2 files changed, 2475 insertions, 0 deletions

diff --git a/drivers/net/tile/Makefile b/drivers/net/tile/Makefile
new file mode 100644
index 00000000000..f634f142cab
--- /dev/null
+++ b/drivers/net/tile/Makefile
@@ -0,0 +1,10 @@
+#
+# Makefile for the TILE on-chip networking support.
+#
+
+obj-$(CONFIG_TILE_NET) += tile_net.o
+ifdef CONFIG_TILEGX
+tile_net-objs := tilegx.o mpipe.o iorpc_mpipe.o dma_queue.o
+else
+tile_net-objs := tilepro.o
+endif
diff --git a/drivers/net/tile/tilepro.c b/drivers/net/tile/tilepro.c
new file mode 100644
index 00000000000..1e2af96fc29
--- /dev/null
+++ b/drivers/net/tile/tilepro.c
@@ -0,0 +1,2465 @@
+/*
+ * Copyright 2011 Tilera Corporation. All Rights Reserved.
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful, but
+ *   WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ *   NON INFRINGEMENT.  See the GNU General Public License for
+ *   more details.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/moduleparam.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>      /* printk() */
+#include <linux/slab.h>        /* kmalloc() */
+#include <linux/errno.h>       /* error codes */
+#include <linux/types.h>       /* size_t */
+#include <linux/interrupt.h>
+#include <linux/in.h>
+#include <linux/netdevice.h>   /* struct device, and other headers */
+#include <linux/etherdevice.h> /* eth_type_trans */
+#include <linux/skbuff.h>
+#include <linux/ioctl.h>
+#include <linux/cdev.h>
+#include <linux/hugetlb.h>
+#include <linux/in6.h>
+#include <linux/timer.h>
+#include <linux/io.h>
+#include <asm/checksum.h>
+#include <asm/homecache.h>
+
+#include <hv/drv_xgbe_intf.h>
+#include <hv/drv_xgbe_impl.h>
+#include <hv/hypervisor.h>
+#include <hv/netio_intf.h>
+
+/* For TSO */
+#include <linux/ip.h>
+#include <linux/tcp.h>
+
+
+/*
+ * First, "tile_net_init_module()" initializes all four "devices" which
+ * can be used by linux.
+ *
+ * Then, "ifconfig DEVICE up" calls "tile_net_open()", which analyzes
+ * the network cpus, then uses "tile_net_open_aux()" to initialize
+ * LIPP/LEPP, and then uses "tile_net_open_inner()" to register all
+ * the tiles, provide buffers to LIPP, allow ingress to start, and
+ * turn on hypervisor interrupt handling (and NAPI) on all tiles.
+ *
+ * If registration fails due to the link being down, then "retry_work"
+ * is used to keep calling "tile_net_open_inner()" until it succeeds.
+ *
+ * If "ifconfig DEVICE down" is called, it uses "tile_net_stop()" to
+ * stop egress, drain the LIPP buffers, unregister all the tiles, stop
+ * LIPP/LEPP, and wipe the LEPP queue.
+ *
+ * We start out with the ingress interrupt enabled on each CPU.  When
+ * this interrupt fires, we disable it, and call "napi_schedule()".
+ * This will cause "tile_net_poll()" to be called, which will pull
+ * packets from the netio queue, filtering them out, or passing them
+ * to "netif_receive_skb()".  If our budget is exhausted, we will
+ * return, knowing we will be called again later.  Otherwise, we
+ * reenable the ingress interrupt, and call "napi_complete()".
+ *
+ * HACK: Since disabling the ingress interrupt is not reliable, we
+ * ignore the interrupt if the global "active" flag is false.
+ *
+ *
+ * NOTE: The use of "native_driver" ensures that EPP exists, and that
+ * we are using "LIPP" and "LEPP".
+ *
+ * NOTE: Failing to free completions for an arbitrarily long time
+ * (which is defined to be illegal) does in fact cause bizarre
+ * problems.  The "egress_timer" helps prevent this from happening.
+ */
+
+
+/* HACK: Allow use of "jumbo" packets. */
+/* This should be 1500 if "jumbo" is not set in LIPP. */
+/* This should be at most 10226 (10240 - 14) if "jumbo" is set in LIPP. */
+/* ISSUE: This has not been thoroughly tested (except at 1500). */
+#define TILE_NET_MTU 1500
+
+/* HACK: Define to support GSO. */
+/* ISSUE: This may actually hurt performance of the TCP blaster. */
+/* #define TILE_NET_GSO */
+
+/* Define this to collapse "duplicate" acks. */
+/* #define IGNORE_DUP_ACKS */
+
+/* HACK: Define this to verify incoming packets. */
+/* #define TILE_NET_VERIFY_INGRESS */
+
+/* Use 3000 to enable the Linux Traffic Control (QoS) layer, else 0. */
+#define TILE_NET_TX_QUEUE_LEN 0
+
+/* Define to dump packets (prints out the whole packet on tx and rx). */
+/* #define TILE_NET_DUMP_PACKETS */
+
+/* Define to enable debug spew (all PDEBUG's are enabled). */
+/* #define TILE_NET_DEBUG */
+
+
+/* Define to activate paranoia checks. */
+/* #define TILE_NET_PARANOIA */
+
+/* Default transmit lockup timeout period, in jiffies. */
+#define TILE_NET_TIMEOUT (5 * HZ)
+
+/* Default retry interval for bringing up the NetIO interface, in jiffies. */
+#define TILE_NET_RETRY_INTERVAL (5 * HZ)
+
+/* Number of ports (xgbe0, xgbe1, gbe0, gbe1). */
+#define TILE_NET_DEVS 4
+
+
+
+/* Paranoia. */
+#if NET_IP_ALIGN != LIPP_PACKET_PADDING
+#error "NET_IP_ALIGN must match LIPP_PACKET_PADDING."
+#endif
+
+
+/* Debug print. */
+#ifdef TILE_NET_DEBUG
+#define PDEBUG(fmt, args...) net_printk(fmt, ## args)
+#else
+#define PDEBUG(fmt, args...)
+#endif
+
+
+MODULE_AUTHOR("Tilera");
+MODULE_LICENSE("GPL");
+
+
+/*
+ * Queue of incoming packets for a specific cpu and device.
+ *
+ * Includes a pointer to the "system" data, and the actual "user" data.
+ */
+struct tile_netio_queue {
+        netio_queue_impl_t *__system_part;
+        netio_queue_user_impl_t __user_part;
+
+};
+
+
+/*
+ * Statistics counters for a specific cpu and device.
+ */
+struct tile_net_stats_t {
+        u32 rx_packets;
+        u32 rx_bytes;
+        u32 tx_packets;
+        u32 tx_bytes;
+};
+
+
+/*
+ * Info for a specific cpu and device.
+ *
+ * ISSUE: There is a "dev" pointer in "napi" as well.
+ */
+struct tile_net_cpu {
+        /* The NAPI struct. */
+        struct napi_struct napi;
+        /* Packet queue. */
+        struct tile_netio_queue queue;
+        /* Statistics. */
+        struct tile_net_stats_t stats;
+        /* True iff NAPI is enabled. */
+        bool napi_enabled;
+        /* True if this tile has succcessfully registered with the IPP. */
+        bool registered;
+        /* True if the link was down last time we tried to register. */
+        bool link_down;
+        /* True if "egress_timer" is scheduled. */
+        bool egress_timer_scheduled;
+        /* Number of small sk_buffs which must still be provided. */
+        unsigned int num_needed_small_buffers;
+        /* Number of large sk_buffs which must still be provided. */
+        unsigned int num_needed_large_buffers;
+        /* A timer for handling egress completions. */
+        struct timer_list egress_timer;
+};
+
+
+/*
+ * Info for a specific device.
+ */
+struct tile_net_priv {
+        /* Our network device. */
+        struct net_device *dev;
+        /* Pages making up the egress queue. */
+        struct page *eq_pages;
+        /* Address of the actual egress queue. */
+        lepp_queue_t *eq;
+        /* Protects "eq". */
+        spinlock_t eq_lock;
+        /* The hypervisor handle for this interface. */
+        int hv_devhdl;
+        /* The intr bit mask that IDs this device. */
+        u32 intr_id;
+        /* True iff "tile_net_open_aux()" has succeeded. */
+        bool partly_opened;
+        /* True iff the device is "active". */
+        bool active;
+        /* Effective network cpus. */
+        struct cpumask network_cpus_map;
+        /* Number of network cpus. */
+        int network_cpus_count;
+        /* Credits per network cpu. */
+        int network_cpus_credits;
+        /* Network stats. */
+        struct net_device_stats stats;
+        /* For NetIO bringup retries. */
+        struct delayed_work retry_work;
+        /* Quick access to per cpu data. */
+        struct tile_net_cpu *cpu[NR_CPUS];
+};
+
+/* Log2 of the number of small pages needed for the egress queue. */
+#define EQ_ORDER  get_order(sizeof(lepp_queue_t))
+/* Size of the egress queue's pages. */
+#define EQ_SIZE   (1 << (PAGE_SHIFT + EQ_ORDER))
+
+/*
+ * The actual devices (xgbe0, xgbe1, gbe0, gbe1).
+ */
+static struct net_device *tile_net_devs[TILE_NET_DEVS];
+
+/*
+ * The "tile_net_cpu" structures for each device.
+ */
+static DEFINE_PER_CPU(struct tile_net_cpu, hv_xgbe0);
+static DEFINE_PER_CPU(struct tile_net_cpu, hv_xgbe1);
+static DEFINE_PER_CPU(struct tile_net_cpu, hv_gbe0);
+static DEFINE_PER_CPU(struct tile_net_cpu, hv_gbe1);
+
+
+/*
+ * True if "network_cpus" was specified.
+ */
+static bool network_cpus_used;
+
+/*
+ * The actual cpus in "network_cpus".
+ */
+static struct cpumask network_cpus_map;
+
+
+
+#ifdef TILE_NET_DEBUG
+/*
+ * printk with extra stuff.
+ *
+ * We print the CPU we're running in brackets.
+ */
+static void net_printk(char *fmt, ...)
+{
+        int i;
+        int len;
+        va_list args;
+        static char buf[256];
+
+        len = sprintf(buf, "tile_net[%2.2d]: ", smp_processor_id());
+        va_start(args, fmt);
+        i = vscnprintf(buf + len, sizeof(buf) - len - 1, fmt, args);
+        va_end(args);
+        buf[255] = '\0';
+        pr_notice(buf);
+}
+#endif
+
+
+#ifdef TILE_NET_DUMP_PACKETS
+/*
+ * Dump a packet.
+ */
+static void dump_packet(unsigned char *data, unsigned long length, char *s)
+{
+        int my_cpu = smp_processor_id();
+
+        unsigned long i;
+        char buf[128];
+
+        static unsigned int count;
+
+        pr_info("dump_packet(data %p, length 0x%lx s %s count 0x%x)\n",
+               data, length, s, count++);
+
+        pr_info("\n");
+
+        for (i = 0; i < length; i++) {
+                if ((i & 0xf) == 0)
+                        sprintf(buf, "[%02d] %8.8lx:", my_cpu, i);
+                sprintf(buf + strlen(buf), " %2.2x", data[i]);
+                if ((i & 0xf) == 0xf || i == length - 1) {
+                        strcat(buf, "\n");
+                        pr_info("%s", buf);
+                }
+        }
+}
+#endif
+
+
+/*
+ * Provide support for the __netio_fastio1() swint
+ * (see <hv/drv_xgbe_intf.h> for how it is used).
+ *
+ * The fastio swint2 call may clobber all the caller-saved registers.
+ * It rarely clobbers memory, but we allow for the possibility in
+ * the signature just to be on the safe side.
+ *
+ * Also, gcc doesn't seem to allow an input operand to be
+ * clobbered, so we fake it with dummy outputs.
+ *
+ * This function can't be static because of the way it is declared
+ * in the netio header.
+ */
+inline int __netio_fastio1(u32 fastio_index, u32 arg0)
+{
+        long result, clobber_r1, clobber_r10;
+        asm volatile("swint2"
+                     : "=R00" (result),
+                       "=R01" (clobber_r1), "=R10" (clobber_r10)
+                     : "R10" (fastio_index), "R01" (arg0)
+                     : "memory", "r2", "r3", "r4",
+                       "r5", "r6", "r7", "r8", "r9",
+                       "r11", "r12", "r13", "r14",
+                       "r15", "r16", "r17", "r18", "r19",
+                       "r20", "r21", "r22", "r23", "r24",
+                       "r25", "r26", "r27", "r28", "r29");
+        return result;
+}
+
+
+/*
+ * Provide a linux buffer to LIPP.
+ */
+static void tile_net_provide_linux_buffer(struct tile_net_cpu *info,
+                                          void *va, bool small)
+{
+        struct tile_netio_queue *queue = &info->queue;
+
+        /* Convert "va" and "small" to "linux_buffer_t". */
+        unsigned int buffer = ((unsigned int)(__pa(va) >> 7) << 1) + small;
+
+        __netio_fastio_free_buffer(queue->__user_part.__fastio_index, buffer);
+}
+
+
+/*
+ * Provide a linux buffer for LIPP.
+ *
+ * Note that the ACTUAL allocation for each buffer is a "struct sk_buff",
+ * plus a chunk of memory that includes not only the requested bytes, but
+ * also NET_SKB_PAD bytes of initial padding, and a "struct skb_shared_info".
+ *
+ * Note that "struct skb_shared_info" is 88 bytes with 64K pages and
+ * 268 bytes with 4K pages (since the frags[] array needs 18 entries).
+ *
+ * Without jumbo packets, the maximum packet size will be 1536 bytes,
+ * and we use 2 bytes (NET_IP_ALIGN) of padding.  ISSUE: If we told
+ * the hardware to clip at 1518 bytes instead of 1536 bytes, then we
+ * could save an entire cache line, but in practice, we don't need it.
+ *
+ * Since CPAs are 38 bits, and we can only encode the high 31 bits in
+ * a "linux_buffer_t", the low 7 bits must be zero, and thus, we must
+ * align the actual "va" mod 128.
+ *
+ * We assume that the underlying "head" will be aligned mod 64.  Note
+ * that in practice, we have seen "head" NOT aligned mod 128 even when
+ * using 2048 byte allocations, which is surprising.
+ *
+ * If "head" WAS always aligned mod 128, we could change LIPP to
+ * assume that the low SIX bits are zero, and the 7th bit is one, that
+ * is, align the actual "va" mod 128 plus 64, which would be "free".
+ *
+ * For now, the actual "head" pointer points at NET_SKB_PAD bytes of
+ * padding, plus 28 or 92 bytes of extra padding, plus the sk_buff
+ * pointer, plus the NET_IP_ALIGN padding, plus 126 or 1536 bytes for
+ * the actual packet, plus 62 bytes of empty padding, plus some
+ * padding and the "struct skb_shared_info".
+ *
+ * With 64K pages, a large buffer thus needs 32+92+4+2+1536+62+88
+ * bytes, or 1816 bytes, which fits comfortably into 2048 bytes.
+ *
+ * With 64K pages, a small buffer thus needs 32+92+4+2+126+88
+ * bytes, or 344 bytes, which means we are wasting 64+ bytes, and
+ * could presumably increase the size of small buffers.
+ *
+ * With 4K pages, a large buffer thus needs 32+92+4+2+1536+62+268
+ * bytes, or 1996 bytes, which fits comfortably into 2048 bytes.
+ *
+ * With 4K pages, a small buffer thus needs 32+92+4+2+126+268
+ * bytes, or 524 bytes, which is annoyingly wasteful.
+ *
+ * Maybe we should increase LIPP_SMALL_PACKET_SIZE to 192?
+ *
+ * ISSUE: Maybe we should increase "NET_SKB_PAD" to 64?
+ */
+static bool tile_net_provide_needed_buffer(struct tile_net_cpu *info,
+                                           bool small)
+{
+#if TILE_NET_MTU <= 1536
+        /* Without "jumbo", 2 + 1536 should be sufficient. */
+        unsigned int large_size = NET_IP_ALIGN + 1536;
+#else
+        /* ISSUE: This has not been tested. */
+        unsigned int large_size = NET_IP_ALIGN + TILE_NET_MTU + 100;
+#endif
+
+        /* Avoid "false sharing" with last cache line. */
+        /* ISSUE: This is already done by "dev_alloc_skb()". */
+        unsigned int len =
+                 (((small ? LIPP_SMALL_PACKET_SIZE : large_size) +
+                   CHIP_L2_LINE_SIZE() - 1) & -CHIP_L2_LINE_SIZE());
+
+        unsigned int padding = 128 - NET_SKB_PAD;
+        unsigned int align;
+
+        struct sk_buff *skb;
+        void *va;
+
+        struct sk_buff **skb_ptr;
+
+        /* Request 96 extra bytes for alignment purposes. */
+        skb = dev_alloc_skb(len + padding);
+        if (skb == NULL)
+                return false;
+
+        /* Skip 32 or 96 bytes to align "data" mod 128. */
+        align = -(long)skb->data & (128 - 1);
+        BUG_ON(align > padding);
+        skb_reserve(skb, align);
+
+        /* This address is given to IPP. */
+        va = skb->data;
+
+        /* Buffers must not span a huge page. */
+        BUG_ON(((((long)va & ~HPAGE_MASK) + len) & HPAGE_MASK) != 0);
+
+#ifdef TILE_NET_PARANOIA
+#if CHIP_HAS_CBOX_HOME_MAP()
+        if (hash_default) {
+                HV_PTE pte = *virt_to_pte(current->mm, (unsigned long)va);
+                if (hv_pte_get_mode(pte) != HV_PTE_MODE_CACHE_HASH_L3)
+                        panic("Non-HFH ingress buffer! VA=%p Mode=%d PTE=%llx",
+                              va, hv_pte_get_mode(pte), hv_pte_val(pte));
+        }
+#endif
+#endif
+
+        /* Invalidate the packet buffer. */
+        if (!hash_default)
+                __inv_buffer(va, len);
+
+        /* Skip two bytes to satisfy LIPP assumptions. */
+        /* Note that this aligns IP on a 16 byte boundary. */
+        /* ISSUE: Do this when the packet arrives? */
+        skb_reserve(skb, NET_IP_ALIGN);
+
+        /* Save a back-pointer to 'skb'. */
+        skb_ptr = va - sizeof(*skb_ptr);
+        *skb_ptr = skb;
+
+        /* Make sure "skb_ptr" has been flushed. */
+        __insn_mf();
+
+        /* Provide the new buffer. */
+        tile_net_provide_linux_buffer(info, va, small);
+
+        return true;
+}
+
+
+/*
+ * Provide linux buffers for LIPP.
+ */
+static void tile_net_provide_needed_buffers(struct tile_net_cpu *info)
+{
+        while (info->num_needed_small_buffers != 0) {
+                if (!tile_net_provide_needed_buffer(info, true))
+                        goto oops;
+                info->num_needed_small_buffers--;
+        }
+
+        while (info->num_needed_large_buffers != 0) {
+                if (!tile_net_provide_needed_buffer(info, false))
+                        goto oops;
+                info->num_needed_large_buffers--;
+        }
+
+        return;
+
+oops:
+
+        /* Add a description to the page allocation failure dump. */
+        pr_notice("Could not provide a linux buffer to LIPP.\n");
+}
+
+
+/*
+ * Grab some LEPP completions, and store them in "comps", of size
+ * "comps_size", and return the number of completions which were
+ * stored, so the caller can free them.
+ */
+static unsigned int tile_net_lepp_grab_comps(lepp_queue_t *eq,
+                                             struct sk_buff *comps[],
+                                             unsigned int comps_size,
+                                             unsigned int min_size)
+{
+        unsigned int n = 0;
+
+        unsigned int comp_head = eq->comp_head;
+        unsigned int comp_busy = eq->comp_busy;
+
+        while (comp_head != comp_busy && n < comps_size) {
+                comps[n++] = eq->comps[comp_head];
+                LEPP_QINC(comp_head);
+        }
+
+        if (n < min_size)
+                return 0;
+
+        eq->comp_head = comp_head;
+
+        return n;
+}
+
+
+/*
+ * Free some comps, and return true iff there are still some pending.
+ */
+static bool tile_net_lepp_free_comps(struct net_device *dev, bool all)
+{
+        struct tile_net_priv *priv = netdev_priv(dev);
+
+        lepp_queue_t *eq = priv->eq;
+
+        struct sk_buff *olds[64];
+        unsigned int wanted = 64;
+        unsigned int i, n;
+        bool pending;
+
+        spin_lock(&priv->eq_lock);
+
+        if (all)
+                eq->comp_busy = eq->comp_tail;
+
+        n = tile_net_lepp_grab_comps(eq, olds, wanted, 0);
+
+        pending = (eq->comp_head != eq->comp_tail);
+
+        spin_unlock(&priv->eq_lock);
+
+        for (i = 0; i < n; i++)
+                kfree_skb(olds[i]);
+
+        return pending;
+}
+
+
+/*
+ * Make sure the egress timer is scheduled.
+ *
+ * Note that we use "schedule if not scheduled" logic instead of the more
+ * obvious "reschedule" logic, because "reschedule" is fairly expensive.
+ */
+static void tile_net_schedule_egress_timer(struct tile_net_cpu *info)
+{
+        if (!info->egress_timer_scheduled) {
+                mod_timer_pinned(&info->egress_timer, jiffies + 1);
+                info->egress_timer_scheduled = true;
+        }
+}
+
+
+/*
+ * The "function" for "info->egress_timer".
+ *
+ * This timer will reschedule itself as long as there are any pending
+ * completions expected (on behalf of any tile).
+ *
+ * ISSUE: Realistically, will the timer ever stop scheduling itself?
+ *
+ * ISSUE: This timer is almost never actually needed, so just use a global
+ * timer that can run on any tile.
+ *
+ * ISSUE: Maybe instead track number of expected completions, and free
+ * only that many, resetting to zero if "pending" is ever false.
+ */
+static void tile_net_handle_egress_timer(unsigned long arg)
+{
+        struct tile_net_cpu *info = (struct tile_net_cpu *)arg;
+        struct net_device *dev = info->napi.dev;
+
+        /* The timer is no longer scheduled. */
+        info->egress_timer_scheduled = false;
+
+        /* Free comps, and reschedule timer if more are pending. */
+        if (tile_net_lepp_free_comps(dev, false))
+                tile_net_schedule_egress_timer(info);
+}
+
+
+#ifdef IGNORE_DUP_ACKS
+
+/*
+ * Help detect "duplicate" ACKs.  These are sequential packets (for a
+ * given flow) which are exactly 66 bytes long, sharing everything but
+ * ID=2@0x12, Hsum=2@0x18, Ack=4@0x2a, WinSize=2@0x30, Csum=2@0x32,
+ * Tstamps=10@0x38.  The ID's are +1, the Hsum's are -1, the Ack's are
+ * +N, and the Tstamps are usually identical.
+ *
+ * NOTE: Apparently truly duplicate acks (with identical "ack" values),
+ * should not be collapsed, as they are used for some kind of flow control.
+ */
+static bool is_dup_ack(char *s1, char *s2, unsigned int len)
+{
+        int i;
+
+        unsigned long long ignorable = 0;
+
+        /* Identification. */
+        ignorable |= (1ULL << 0x12);
+        ignorable |= (1ULL << 0x13);
+
+        /* Header checksum. */
+        ignorable |= (1ULL << 0x18);
+        ignorable |= (1ULL << 0x19);
+
+        /* ACK. */
+        ignorable |= (1ULL << 0x2a);
+        ignorable |= (1ULL << 0x2b);
+        ignorable |= (1ULL << 0x2c);
+        ignorable |= (1ULL << 0x2d);
+
+        /* WinSize. */
+        ignorable |= (1ULL << 0x30);
+        ignorable |= (1ULL << 0x31);
+
+        /* Checksum. */
+        ignorable |= (1ULL << 0x32);
+        ignorable |= (1ULL << 0x33);
+
+        for (i = 0; i < len; i++, ignorable >>= 1) {
+
+                if ((ignorable & 1) || (s1[i] == s2[i]))
+                        continue;
+
+#ifdef TILE_NET_DEBUG
+                /* HACK: Mention non-timestamp diffs. */
+                if (i < 0x38 && i != 0x2f &&
+                    net_ratelimit())
+                        pr_info("Diff at 0x%x\n", i);
+#endif
+
+                return false;
+        }
+
+#ifdef TILE_NET_NO_SUPPRESS_DUP_ACKS
+        /* HACK: Do not suppress truly duplicate ACKs. */
+        /* ISSUE: Is this actually necessary or helpful? */
+        if (s1[0x2a] == s2[0x2a] &&
+            s1[0x2b] == s2[0x2b] &&
+            s1[0x2c] == s2[0x2c] &&
+            s1[0x2d] == s2[0x2d]) {
+                return false;
+        }
+#endif
+
+        return true;
+}
+
+#endif
+
+
+
+static void tile_net_discard_aux(struct tile_net_cpu *info, int index)
+{
+        struct tile_netio_queue *queue = &info->queue;
+        netio_queue_impl_t *qsp = queue->__system_part;
+        netio_queue_user_impl_t *qup = &queue->__user_part;
+
+        int index2_aux = index + sizeof(netio_pkt_t);
+        int index2 =
+                ((index2_aux ==
+                  qsp->__packet_receive_queue.__last_packet_plus_one) ?
+                 0 : index2_aux);
+
+        netio_pkt_t *pkt = (netio_pkt_t *)((unsigned long) &qsp[1] + index);
+
+        /* Extract the "linux_buffer_t". */
+        unsigned int buffer = pkt->__packet.word;
+
+        /* Convert "linux_buffer_t" to "va". */
+        void *va = __va((phys_addr_t)(buffer >> 1) << 7);
+
+        /* Acquire the associated "skb". */
+        struct sk_buff **skb_ptr = va - sizeof(*skb_ptr);
+        struct sk_buff *skb = *skb_ptr;
+
+        kfree_skb(skb);
+
+        /* Consume this packet. */
+        qup->__packet_receive_read = index2;
+}
+
+
+/*
+ * Like "tile_net_poll()", but just discard packets.
+ */
+static void tile_net_discard_packets(struct net_device *dev)
+{
+        struct tile_net_priv *priv = netdev_priv(dev);
+        int my_cpu = smp_processor_id();
+        struct tile_net_cpu *info = priv->cpu[my_cpu];
+        struct tile_netio_queue *queue = &info->queue;
+        netio_queue_impl_t *qsp = queue->__system_part;
+        netio_queue_user_impl_t *qup = &queue->__user_part;
+
+        while (qup->__packet_receive_read !=
+               qsp->__packet_receive_queue.__packet_write) {
+                int index = qup->__packet_receive_read;
+                tile_net_discard_aux(info, index);
+        }
+}
+
+
+/*
+ * Handle the next packet.  Return true if "processed", false if "filtered".
+ */
+static bool tile_net_poll_aux(struct tile_net_cpu *info, int index)
+{
+        struct net_device *dev = info->napi.dev;
+
+        struct tile_netio_queue *queue = &info->queue;
+        netio_queue_impl_t *qsp = queue->__system_part;
+        netio_queue_user_impl_t *qup = &queue->__user_part;
+        struct tile_net_stats_t *stats = &info->stats;
+
+        int filter;
+
+        int index2_aux = index + sizeof(netio_pkt_t);
+        int index2 =
+                ((index2_aux ==
+                  qsp->__packet_receive_queue.__last_packet_plus_one) ?
+                 0 : index2_aux);
+
+        netio_pkt_t *pkt = (netio_pkt_t *)((unsigned long) &qsp[1] + index);
+
+        netio_pkt_metadata_t *metadata = NETIO_PKT_METADATA(pkt);
+
+        /* Extract the packet size.  FIXME: Shouldn't the second line */
+        /* get subtracted?  Mostly moot, since it should be "zero". */
+        unsigned long len =
+                (NETIO_PKT_CUSTOM_LENGTH(pkt) +
+                 NET_IP_ALIGN - NETIO_PACKET_PADDING);
+
+        /* Extract the "linux_buffer_t". */
+        unsigned int buffer = pkt->__packet.word;
+
+        /* Extract "small" (vs "large"). */
+        bool small = ((buffer & 1) != 0);
+
+        /* Convert "linux_buffer_t" to "va". */
+        void *va = __va((phys_addr_t)(buffer >> 1) << 7);
+
+        /* Extract the packet data pointer. */
+        /* Compare to "NETIO_PKT_CUSTOM_DATA(pkt)". */
+        unsigned char *buf = va + NET_IP_ALIGN;
+
+        /* Invalidate the packet buffer. */
+        if (!hash_default)
+                __inv_buffer(buf, len);
+
+        /* ISSUE: Is this needed? */
+        dev->last_rx = jiffies;
+
+#ifdef TILE_NET_DUMP_PACKETS
+        dump_packet(buf, len, "rx");
+#endif /* TILE_NET_DUMP_PACKETS */
+
+#ifdef TILE_NET_VERIFY_INGRESS
+        if (!NETIO_PKT_L4_CSUM_CORRECT_M(metadata, pkt) &&
+            NETIO_PKT_L4_CSUM_CALCULATED_M(metadata, pkt)) {
+                /* Bug 6624: Includes UDP packets with a "zero" checksum. */
+                pr_warning("Bad L4 checksum on %d byte packet.\n", len);
+        }
+        if (!NETIO_PKT_L3_CSUM_CORRECT_M(metadata, pkt) &&
+            NETIO_PKT_L3_CSUM_CALCULATED_M(metadata, pkt)) {
+                dump_packet(buf, len, "rx");
+                panic("Bad L3 checksum.");
+        }
+        switch (NETIO_PKT_STATUS_M(metadata, pkt)) {
+        case NETIO_PKT_STATUS_OVERSIZE:
+                if (len >= 64) {
+                        dump_packet(buf, len, "rx");
+                        panic("Unexpected OVERSIZE.");
+                }
+                break;
+        case NETIO_PKT_STATUS_BAD:
+                pr_warning("Unexpected BAD %ld byte packet.\n", len);
+        }
+#endif
+
+        filter = 0;
+
+        /* ISSUE: Filter TCP packets with "bad" checksums? */
+
+        if (!(dev->flags & IFF_UP)) {
+                /* Filter packets received before we're up. */
+                filter = 1;
+        } else if (NETIO_PKT_STATUS_M(metadata, pkt) == NETIO_PKT_STATUS_BAD) {
+                /* Filter "truncated" packets. */
+                filter = 1;
+        } else if (!(dev->flags & IFF_PROMISC)) {
+                /* FIXME: Implement HW multicast filter. */
+                if (!is_multicast_ether_addr(buf)) {
+                        /* Filter packets not for our address. */
+                        const u8 *mine = dev->dev_addr;
+                        filter = compare_ether_addr(mine, buf);
+                }
+        }
+
+        if (filter) {
+
+                /* ISSUE: Update "drop" statistics? */
+
+                tile_net_provide_linux_buffer(info, va, small);
+
+        } else {
+
+                /* Acquire the associated "skb". */
+                struct sk_buff **skb_ptr = va - sizeof(*skb_ptr);
+                struct sk_buff *skb = *skb_ptr;
+
+                /* Paranoia. */
+                if (skb->data != buf)
+                        panic("Corrupt linux buffer from LIPP! "
+                              "VA=%p, skb=%p, skb->data=%p\n",
+                              va, skb, skb->data);
+
+                /* Encode the actual packet length. */
+                skb_put(skb, len);
+
+                /* NOTE: This call also sets "skb->dev = dev". */
+                skb->protocol = eth_type_trans(skb, dev);
+
+                /* Avoid recomputing "good" TCP/UDP checksums. */
+                if (NETIO_PKT_L4_CSUM_CORRECT_M(metadata, pkt))
+                        skb->ip_summed = CHECKSUM_UNNECESSARY;
+
+                netif_receive_skb(skb);
+
+                stats->rx_packets++;
+                stats->rx_bytes += len;
+
+                if (small)
+                        info->num_needed_small_buffers++;
+                else
+                        info->num_needed_large_buffers++;
+        }
+
+        /* Return four credits after every fourth packet. */
+        if (--qup->__receive_credit_remaining == 0) {
+                u32 interval = qup->__receive_credit_interval;
+                qup->__receive_credit_remaining = interval;
+                __netio_fastio_return_credits(qup->__fastio_index, interval);
+        }
+
+        /* Consume this packet. */
+        qup->__packet_receive_read = index2;
+
+        return !filter;
+}
+
+
+/*
+ * Handle some packets for the given device on the current CPU.
+ *
+ * If "tile_net_stop()" is called on some other tile while this
+ * function is running, we will return, hopefully before that
+ * other tile asks us to call "napi_disable()".
+ *
+ * The "rotting packet" race condition occurs if a packet arrives
+ * during the extremely narrow window between the queue appearing to
+ * be empty, and the ingress interrupt being re-enabled.  This happens
+ * a LOT under heavy network load.
+ */
+static int tile_net_poll(struct napi_struct *napi, int budget)
+{
+        struct net_device *dev = napi->dev;
+        struct tile_net_priv *priv = netdev_priv(dev);
+        int my_cpu = smp_processor_id();
+        struct tile_net_cpu *info = priv->cpu[my_cpu];
+        struct tile_netio_queue *queue = &info->queue;
+        netio_queue_impl_t *qsp = queue->__system_part;
+        netio_queue_user_impl_t *qup = &queue->__user_part;
+
+        unsigned int work = 0;
+
+        while (priv->active) {
+                int index = qup->__packet_receive_read;
+                if (index == qsp->__packet_receive_queue.__packet_write)
+                        break;
+
+                if (tile_net_poll_aux(info, index)) {
+                        if (++work >= budget)
+                                goto done;
+                }
+        }
+
+        napi_complete(&info->napi);
+
+        if (!priv->active)
+                goto done;
+
+        /* Re-enable the ingress interrupt. */
+        enable_percpu_irq(priv->intr_id);
+
+        /* HACK: Avoid the "rotting packet" problem (see above). */
+        if (qup->__packet_receive_read !=
+            qsp->__packet_receive_queue.__packet_write) {
+                /* ISSUE: Sometimes this returns zero, presumably */
+                /* because an interrupt was handled for this tile. */
+                (void)napi_reschedule(&info->napi);
+        }
+
+done:
+
+        if (priv->active)
+                tile_net_provide_needed_buffers(info);
+
+        return work;
+}
+
+
+/*
+ * Handle an ingress interrupt for the given device on the current cpu.
+ *
+ * ISSUE: Sometimes this gets called after "disable_percpu_irq()" has
+ * been called!  This is probably due to "pending hypervisor downcalls".
+ *
+ * ISSUE: Is there any race condition between the "napi_schedule()" here
+ * and the "napi_complete()" call above?
+ */
+static irqreturn_t tile_net_handle_ingress_interrupt(int irq, void *dev_ptr)
+{
+        struct net_device *dev = (struct net_device *)dev_ptr;
+        struct tile_net_priv *priv = netdev_priv(dev);
+        int my_cpu = smp_processor_id();
+        struct tile_net_cpu *info = priv->cpu[my_cpu];
+
+        /* Disable the ingress interrupt. */
+        disable_percpu_irq(priv->intr_id);
+
+        /* Ignore unwanted interrupts. */
+        if (!priv->active)
+                return IRQ_HANDLED;
+
+        /* ISSUE: Sometimes "info->napi_enabled" is false here. */
+
+        napi_schedule(&info->napi);
+
+        return IRQ_HANDLED;
+}
+
+
+/*
+ * One time initialization per interface.
+ */
+static int tile_net_open_aux(struct net_device *dev)
+{
+        struct tile_net_priv *priv = netdev_priv(dev);
+
+        int ret;
+        int dummy;
+        unsigned int epp_lotar;
+
+        /*
+         * Find out where EPP memory should be homed.
+         */
+        ret = hv_dev_pread(priv->hv_devhdl, 0,
+                           (HV_VirtAddr)&epp_lotar, sizeof(epp_lotar),
+                           NETIO_EPP_SHM_OFF);
+        if (ret < 0) {
+                pr_err("could not read epp_shm_queue lotar.\n");
+                return -EIO;
+        }
+
+        /*
+         * Home the page on the EPP.
+         */
+        {
+                int epp_home = hv_lotar_to_cpu(epp_lotar);
+                homecache_change_page_home(priv->eq_pages, EQ_ORDER, epp_home);
+        }
+
+        /*
+         * Register the EPP shared memory queue.
+         */
+        {
+                netio_ipp_address_t ea = {
+                        .va = 0,
+                        .pa = __pa(priv->eq),
+                        .pte = hv_pte(0),
+                        .size = EQ_SIZE,
+                };
+                ea.pte = hv_pte_set_lotar(ea.pte, epp_lotar);
+                ea.pte = hv_pte_set_mode(ea.pte, HV_PTE_MODE_CACHE_TILE_L3);
+                ret = hv_dev_pwrite(priv->hv_devhdl, 0,
+                                    (HV_VirtAddr)&ea,
+                                    sizeof(ea),
+                                    NETIO_EPP_SHM_OFF);
+                if (ret < 0)
+                        return -EIO;
+        }
+
+        /*
+         * Start LIPP/LEPP.
+         */
+        if (hv_dev_pwrite(priv->hv_devhdl, 0, (HV_VirtAddr)&dummy,
+                          sizeof(dummy), NETIO_IPP_START_SHIM_OFF) < 0) {
+                pr_warning("Failed to start LIPP/LEPP.\n");
+                return -EIO;
+        }
+
+        return 0;
+}
+
+
+/*
+ * Register with hypervisor on the current CPU.
+ *
+ * Strangely, this function does important things even if it "fails",
+ * which is especially common if the link is not up yet.  Hopefully
+ * these things are all "harmless" if done twice!
+ */
+static void tile_net_register(void *dev_ptr)
+{
+        struct net_device *dev = (struct net_device *)dev_ptr;
+        struct tile_net_priv *priv = netdev_priv(dev);
+        int my_cpu = smp_processor_id();
+        struct tile_net_cpu *info;
+
+        struct tile_netio_queue *queue;
+
+        /* Only network cpus can receive packets. */
+        int queue_id =
+                cpumask_test_cpu(my_cpu, &priv->network_cpus_map) ? 0 : 255;
+
+        netio_input_config_t config = {
+                .flags = 0,
+                .num_receive_packets = priv->network_cpus_credits,
+                .queue_id = queue_id
+        };
+
+        int ret = 0;
+        netio_queue_impl_t *queuep;
+
+        PDEBUG("tile_net_register(queue_id %d)\n", queue_id);
+
+        if (!strcmp(dev->name, "xgbe0"))
+                info = &__get_cpu_var(hv_xgbe0);
+        else if (!strcmp(dev->name, "xgbe1"))
+                info = &__get_cpu_var(hv_xgbe1);
+        else if (!strcmp(dev->name, "gbe0"))
+                info = &__get_cpu_var(hv_gbe0);
+        else if (!strcmp(dev->name, "gbe1"))
+                info = &__get_cpu_var(hv_gbe1);
+        else
+                BUG();
+
+        /* Initialize the egress timer. */
+        init_timer(&info->egress_timer);
+        info->egress_timer.data = (long)info;
+        info->egress_timer.function = tile_net_handle_egress_timer;
+
+        priv->cpu[my_cpu] = info;
+
+        /*
+         * Register ourselves with LIPP.  This does a lot of stuff,
+         * including invoking the LIPP registration code.
+         */
+        ret = hv_dev_pwrite(priv->hv_devhdl, 0,
+                            (HV_VirtAddr)&config,
+                            sizeof(netio_input_config_t),
+                            NETIO_IPP_INPUT_REGISTER_OFF);
+        PDEBUG("hv_dev_pwrite(NETIO_IPP_INPUT_REGISTER_OFF) returned %d\n",
+               ret);
+        if (ret < 0) {
+                if (ret != NETIO_LINK_DOWN) {
+                        printk(KERN_DEBUG "hv_dev_pwrite "
+                               "NETIO_IPP_INPUT_REGISTER_OFF failure %d\n",
+                               ret);
+                }
+                info->link_down = (ret == NETIO_LINK_DOWN);
+                return;
+        }
+
+        /*
+         * Get the pointer to our queue's system part.
+         */
+
+        ret = hv_dev_pread(priv->hv_devhdl, 0,
+                           (HV_VirtAddr)&queuep,
+                           sizeof(netio_queue_impl_t *),
+                           NETIO_IPP_INPUT_REGISTER_OFF);
+        PDEBUG("hv_dev_pread(NETIO_IPP_INPUT_REGISTER_OFF) returned %d\n",
+               ret);
+        PDEBUG("queuep %p\n", queuep);
+        if (ret <= 0) {
+                /* ISSUE: Shouldn't this be a fatal error? */
+                pr_err("hv_dev_pread NETIO_IPP_INPUT_REGISTER_OFF failure\n");
+                return;
+        }
+
+        queue = &info->queue;
+
+        queue->__system_part = queuep;
+
+        memset(&queue->__user_part, 0, sizeof(netio_queue_user_impl_t));
+
+        /* This is traditionally "config.num_receive_packets / 2". */
+        queue->__user_part.__receive_credit_interval = 4;
+        queue->__user_part.__receive_credit_remaining =
+                queue->__user_part.__receive_credit_interval;
+
+        /*
+         * Get a fastio index from the hypervisor.
+         * ISSUE: Shouldn't this check the result?
+         */
+        ret = hv_dev_pread(priv->hv_devhdl, 0,
+                           (HV_VirtAddr)&queue->__user_part.__fastio_index,
+                           sizeof(queue->__user_part.__fastio_index),
+                           NETIO_IPP_GET_FASTIO_OFF);
+        PDEBUG("hv_dev_pread(NETIO_IPP_GET_FASTIO_OFF) returned %d\n", ret);
+
+        /* Now we are registered. */
+        info->registered = true;
+}
+
+
+/*
+ * Deregister with hypervisor on the current CPU.
+ *
+ * This simply discards all our credits, so no more packets will be
+ * delivered to this tile.  There may still be packets in our queue.
+ *
+ * Also, disable the ingress interrupt.
+ */
+static void tile_net_deregister(void *dev_ptr)
+{
+        struct net_device *dev = (struct net_device *)dev_ptr;
+        struct tile_net_priv *priv = netdev_priv(dev);
+        int my_cpu = smp_processor_id();
+        struct tile_net_cpu *info = priv->cpu[my_cpu];
+
+        /* Disable the ingress interrupt. */
+        disable_percpu_irq(priv->intr_id);
+
+        /* Do nothing else if not registered. */
+        if (info == NULL || !info->registered)
+                return;
+
+        {
+                struct tile_netio_queue *queue = &info->queue;
+                netio_queue_user_impl_t *qup = &queue->__user_part;
+
+                /* Discard all our credits. */
+                __netio_fastio_return_credits(qup->__fastio_index, -1);
+        }
+}
+
+
+/*
+ * Unregister with hypervisor on the current CPU.
+ *
+ * Also, disable the ingress interrupt.
+ */
+static void tile_net_unregister(void *dev_ptr)
+{
+        struct net_device *dev = (struct net_device *)dev_ptr;
+        struct tile_net_priv *priv = netdev_priv(dev);
+        int my_cpu = smp_processor_id();
+        struct tile_net_cpu *info = priv->cpu[my_cpu];
+
+        int ret;
+        int dummy = 0;
+
+        /* Disable the ingress interrupt. */
+        disable_percpu_irq(priv->intr_id);
+
+        /* Do nothing else if not registered. */
+        if (info == NULL || !info->registered)
+                return;
+
+        /* Unregister ourselves with LIPP/LEPP. */
+        ret = hv_dev_pwrite(priv->hv_devhdl, 0, (HV_VirtAddr)&dummy,
+                            sizeof(dummy), NETIO_IPP_INPUT_UNREGISTER_OFF);
+        if (ret < 0)
+                panic("Failed to unregister with LIPP/LEPP!\n");
+
+        /* Discard all packets still in our NetIO queue. */
+        tile_net_discard_packets(dev);
+
+        /* Reset state. */
+        info->num_needed_small_buffers = 0;
+        info->num_needed_large_buffers = 0;
+
+        /* Cancel egress timer. */
+        del_timer(&info->egress_timer);
+        info->egress_timer_scheduled = false;
+}
+
+
+/*
+ * Helper function for "tile_net_stop()".
+ *
+ * Also used to handle registration failure in "tile_net_open_inner()",
+ * when the various extra steps in "tile_net_stop()" are not necessary.
+ */
+static void tile_net_stop_aux(struct net_device *dev)
+{
+        struct tile_net_priv *priv = netdev_priv(dev);
+        int i;
+
+        int dummy = 0;
+
+        /*
+         * Unregister all tiles, so LIPP will stop delivering packets.
+         * Also, delete all the "napi" objects (sequentially, to protect
+         * "dev->napi_list").
+         */
+        on_each_cpu(tile_net_unregister, (void *)dev, 1);
+        for_each_online_cpu(i) {
+                struct tile_net_cpu *info = priv->cpu[i];
+                if (info != NULL && info->registered) {
+                        netif_napi_del(&info->napi);
+                        info->registered = false;
+                }
+        }
+
+        /* Stop LIPP/LEPP. */
+        if (hv_dev_pwrite(priv->hv_devhdl, 0, (HV_VirtAddr)&dummy,
+                          sizeof(dummy), NETIO_IPP_STOP_SHIM_OFF) < 0)
+                panic("Failed to stop LIPP/LEPP!\n");
+
+        priv->partly_opened = 0;
+}
+
+
+/*
+ * Disable NAPI for the given device on the current cpu.
+ */
+static void tile_net_stop_disable(void *dev_ptr)
+{
+        struct net_device *dev = (struct net_device *)dev_ptr;
+        struct tile_net_priv *priv = netdev_priv(dev);
+        int my_cpu = smp_processor_id();
+        struct tile_net_cpu *info = priv->cpu[my_cpu];
+
+        /* Disable NAPI if needed. */
+        if (info != NULL && info->napi_enabled) {
+                napi_disable(&info->napi);
+                info->napi_enabled = false;
+        }
+}
+
+
+/*
+ * Enable NAPI and the ingress interrupt for the given device
+ * on the current cpu.
+ *
+ * ISSUE: Only do this for "network cpus"?
+ */
+static void tile_net_open_enable(void *dev_ptr)
+{
+        struct net_device *dev = (struct net_device *)dev_ptr;
+        struct tile_net_priv *priv = netdev_priv(dev);
+        int my_cpu = smp_processor_id();
+        struct tile_net_cpu *info = priv->cpu[my_cpu];
+
+        /* Enable NAPI. */
+        napi_enable(&info->napi);
+        info->napi_enabled = true;
+
+        /* Enable the ingress interrupt. */
+        enable_percpu_irq(priv->intr_id);
+}
+
+
+/*
+ * tile_net_open_inner does most of the work of bringing up the interface.
+ * It's called from tile_net_open(), and also from tile_net_retry_open().
+ * The return value is 0 if the interface was brought up, < 0 if
+ * tile_net_open() should return the return value as an error, and > 0 if
+ * tile_net_open() should return success and schedule a work item to
+ * periodically retry the bringup.
+ */
+static int tile_net_open_inner(struct net_device *dev)
+{
+        struct tile_net_priv *priv = netdev_priv(dev);
+        int my_cpu = smp_processor_id();
+        struct tile_net_cpu *info;
+        struct tile_netio_queue *queue;
+        int result = 0;
+        int i;
+        int dummy = 0;
+
+        /*
+         * First try to register just on the local CPU, and handle any
+         * semi-expected "link down" failure specially.  Note that we
+         * do NOT call "tile_net_stop_aux()", unlike below.
+         */
+        tile_net_register(dev);
+        info = priv->cpu[my_cpu];
+        if (!info->registered) {
+                if (info->link_down)
+                        return 1;
+                return -EAGAIN;
+        }
+
+        /*
+         * Now register everywhere else.  If any registration fails,
+         * even for "link down" (which might not be possible), we
+         * clean up using "tile_net_stop_aux()".  Also, add all the
+         * "napi" objects (sequentially, to protect "dev->napi_list").
+         * ISSUE: Only use "netif_napi_add()" for "network cpus"?
+         */
+        smp_call_function(tile_net_register, (void *)dev, 1);
+        for_each_online_cpu(i) {
+                struct tile_net_cpu *info = priv->cpu[i];
+                if (info->registered)
+                        netif_napi_add(dev, &info->napi, tile_net_poll, 64);
+                else
+                        result = -EAGAIN;
+        }
+        if (result != 0) {
+                tile_net_stop_aux(dev);
+                return result;
+        }
+
+        queue = &info->queue;
+
+        if (priv->intr_id == 0) {
+                unsigned int irq;
+
+                /*
+                 * Acquire the irq allocated by the hypervisor.  Every
+                 * queue gets the same irq.  The "__intr_id" field is
+                 * "1 << irq", so we use "__ffs()" to extract "irq".
+                 */
+                priv->intr_id = queue->__system_part->__intr_id;
+                BUG_ON(priv->intr_id == 0);
+                irq = __ffs(priv->intr_id);
+
+                /*
+                 * Register the ingress interrupt handler for this
+                 * device, permanently.
+                 *
+                 * We used to call "free_irq()" in "tile_net_stop()",
+                 * and then re-register the handler here every time,
+                 * but that caused DNP errors in "handle_IRQ_event()"
+                 * because "desc->action" was NULL.  See bug 9143.
+                 */
+                tile_irq_activate(irq, TILE_IRQ_PERCPU);
+                BUG_ON(request_irq(irq, tile_net_handle_ingress_interrupt,
+                                   0, dev->name, (void *)dev) != 0);
+        }
+
+        {
+                /* Allocate initial buffers. */
+
+                int max_buffers =
+                        priv->network_cpus_count * priv->network_cpus_credits;
+
+                info->num_needed_small_buffers =
+                        min(LIPP_SMALL_BUFFERS, max_buffers);
+
+                info->num_needed_large_buffers =
+                        min(LIPP_LARGE_BUFFERS, max_buffers);
+
+                tile_net_provide_needed_buffers(info);
+
+                if (info->num_needed_small_buffers != 0 ||
+                    info->num_needed_large_buffers != 0)
+                        panic("Insufficient memory for buffer stack!");
+        }
+
+        /* We are about to be active. */
+        priv->active = true;
+
+        /* Make sure "active" is visible to all tiles. */
+        mb();
+
+        /* On each tile, enable NAPI and the ingress interrupt. */
+        on_each_cpu(tile_net_open_enable, (void *)dev, 1);
+
+        /* Start LIPP/LEPP and activate "ingress" at the shim. */
+        if (hv_dev_pwrite(priv->hv_devhdl, 0, (HV_VirtAddr)&dummy,
+                          sizeof(dummy), NETIO_IPP_INPUT_INIT_OFF) < 0)
+                panic("Failed to activate the LIPP Shim!\n");
+
+        /* Start our transmit queue. */
+        netif_start_queue(dev);
+
+        return 0;
+}
+
+
+/*
+ * Called periodically to retry bringing up the NetIO interface,
+ * if it doesn't come up cleanly during tile_net_open().
+ */
+static void tile_net_open_retry(struct work_struct *w)
+{
+        struct delayed_work *dw =
+                container_of(w, struct delayed_work, work);
+
+        struct tile_net_priv *priv =
+                container_of(dw, struct tile_net_priv, retry_work);
+
+        /*
+         * Try to bring the NetIO interface up.  If it fails, reschedule
+         * ourselves to try again later; otherwise, tell Linux we now have
+         * a working link.  ISSUE: What if the return value is negative?
+         */
+        if (tile_net_open_inner(priv->dev) != 0)
+                schedule_delayed_work(&priv->retry_work,
+                                      TILE_NET_RETRY_INTERVAL);
+        else
+                netif_carrier_on(priv->dev);
+}
+
+
+/*
+ * Called when a network interface is made active.
+ *
+ * Returns 0 on success, negative value on failure.
+ *
+ * The open entry point is called when a network interface is made
+ * active by the system (IFF_UP).  At this point all resources needed
+ * for transmit and receive operations are allocated, the interrupt
+ * handler is registered with the OS (if needed), the watchdog timer
+ * is started, and the stack is notified that the interface is ready.
+ *
+ * If the actual link is not available yet, then we tell Linux that
+ * we have no carrier, and we keep checking until the link comes up.
+ */
+static int tile_net_open(struct net_device *dev)
+{
+        int ret = 0;
+        struct tile_net_priv *priv = netdev_priv(dev);
+
+        /*
+         * We rely on priv->partly_opened to tell us if this is the
+         * first time this interface is being brought up. If it is
+         * set, the IPP was already initialized and should not be
+         * initialized again.
+         */
+        if (!priv->partly_opened) {
+
+                int count;
+                int credits;
+
+                /* Initialize LIPP/LEPP, and start the Shim. */
+                ret = tile_net_open_aux(dev);
+                if (ret < 0) {
+                        pr_err("tile_net_open_aux failed: %d\n", ret);
+                        return ret;
+                }
+
+                /* Analyze the network cpus. */
+
+                if (network_cpus_used)
+                        cpumask_copy(&priv->network_cpus_map,
+                                     &network_cpus_map);
+                else
+                        cpumask_copy(&priv->network_cpus_map, cpu_online_mask);
+
+
+                count = cpumask_weight(&priv->network_cpus_map);
+
+                /* Limit credits to available buffers, and apply min. */
+                credits = max(16, (LIPP_LARGE_BUFFERS / count) & ~1);
+
+                /* Apply "GBE" max limit. */
+                /* ISSUE: Use higher limit for XGBE? */
+                credits = min(NETIO_MAX_RECEIVE_PKTS, credits);
+
+                priv->network_cpus_count = count;
+                priv->network_cpus_credits = credits;
+
+#ifdef TILE_NET_DEBUG
+                pr_info("Using %d network cpus, with %d credits each\n",
+                       priv->network_cpus_count, priv->network_cpus_credits);
+#endif
+
+                priv->partly_opened = 1;
+
+        } else {
+                /* FIXME: Is this possible? */
+                /* printk("Already partly opened.\n"); */
+        }
+
+        /*
+         * Attempt to bring up the link.
+         */
+        ret = tile_net_open_inner(dev);
+        if (ret <= 0) {
+                if (ret == 0)
+                        netif_carrier_on(dev);
+                return ret;
+        }
+
+        /*
+         * We were unable to bring up the NetIO interface, but we want to
+         * try again in a little bit.  Tell Linux that we have no carrier
+         * so it doesn't try to use the interface before the link comes up
+         * and then remember to try again later.
+         */
+        netif_carrier_off(dev);
+        schedule_delayed_work(&priv->retry_work, TILE_NET_RETRY_INTERVAL);
+
+        return 0;
+}
+
+
+static int tile_net_drain_lipp_buffers(struct tile_net_priv *priv)
+{
+        int n = 0;
+
+        /* Drain all the LIPP buffers. */
+        while (true) {
+                int buffer;
+
+                /* NOTE: This should never fail. */
+                if (hv_dev_pread(priv->hv_devhdl, 0, (HV_VirtAddr)&buffer,
+                                 sizeof(buffer), NETIO_IPP_DRAIN_OFF) < 0)
+                        break;
+
+                /* Stop when done. */
+                if (buffer == 0)
+                        break;
+
+                {
+                        /* Convert "linux_buffer_t" to "va". */
+                        void *va = __va((phys_addr_t)(buffer >> 1) << 7);
+
+                        /* Acquire the associated "skb". */
+                        struct sk_buff **skb_ptr = va - sizeof(*skb_ptr);
+                        struct sk_buff *skb = *skb_ptr;
+
+                        kfree_skb(skb);
+                }
+
+                n++;
+        }
+
+        return n;
+}
+
+
+/*
+ * Disables a network interface.
+ *
+ * Returns 0, this is not allowed to fail.
+ *
+ * The close entry point is called when an interface is de-activated
+ * by the OS.  The hardware is still under the drivers control, but
+ * needs to be disabled.  A global MAC reset is issued to stop the
+ * hardware, and all transmit and receive resources are freed.
+ *
+ * ISSUE: How closely does "netif_running(dev)" mirror "priv->active"?
+ *
+ * Before we are called by "__dev_close()", "netif_running()" will
+ * have been cleared, so no NEW calls to "tile_net_poll()" will be
+ * made by "netpoll_poll_dev()".
+ *
+ * Often, this can cause some tiles to still have packets in their
+ * queues, so we must call "tile_net_discard_packets()" later.
+ *
+ * Note that some other tile may still be INSIDE "tile_net_poll()",
+ * and in fact, many will be, if there is heavy network load.
+ *
+ * Calling "on_each_cpu(tile_net_stop_disable, (void *)dev, 1)" when
+ * any tile is still "napi_schedule()"'d will induce a horrible crash
+ * when "msleep()" is called.  This includes tiles which are inside
+ * "tile_net_poll()" which have not yet called "napi_complete()".
+ *
+ * So, we must first try to wait long enough for other tiles to finish
+ * with any current "tile_net_poll()" call, and, hopefully, to clear
+ * the "scheduled" flag.  ISSUE: It is unclear what happens to tiles
+ * which have called "napi_schedule()" but which had not yet tried to
+ * call "tile_net_poll()", or which exhausted their budget inside
+ * "tile_net_poll()" just before this function was called.
+ */
+static int tile_net_stop(struct net_device *dev)
+{
+        struct tile_net_priv *priv = netdev_priv(dev);
+
+        PDEBUG("tile_net_stop()\n");
+
+        /* Start discarding packets. */
+        priv->active = false;
+
+        /* Make sure "active" is visible to all tiles. */
+        mb();
+
+        /*
+         * On each tile, make sure no NEW packets get delivered, and
+         * disable the ingress interrupt.
+         *
+         * Note that the ingress interrupt can fire AFTER this,
+         * presumably due to packets which were recently delivered,
+         * but it will have no effect.
+         */
+        on_each_cpu(tile_net_deregister, (void *)dev, 1);
+
+        /* Optimistically drain LIPP buffers. */
+        (void)tile_net_drain_lipp_buffers(priv);
+
+        /* ISSUE: Only needed if not yet fully open. */
+        cancel_delayed_work_sync(&priv->retry_work);
+
+        /* Can't transmit any more. */
+        netif_stop_queue(dev);
+
+        /* Disable NAPI on each tile. */
+        on_each_cpu(tile_net_stop_disable, (void *)dev, 1);
+
+        /*
+         * Drain any remaining LIPP buffers.  NOTE: This "printk()"
+         * has never been observed, but in theory it could happen.
+         */
+        if (tile_net_drain_lipp_buffers(priv) != 0)
+                printk("Had to drain some extra LIPP buffers!\n");
+
+        /* Stop LIPP/LEPP. */
+        tile_net_stop_aux(dev);
+
+        /*
+         * ISSUE: It appears that, in practice anyway, by the time we
+         * get here, there are no pending completions, but just in case,
+         * we free (all of) them anyway.
+         */
+        while (tile_net_lepp_free_comps(dev, true))
+                /* loop */;
+
+        /* Wipe the EPP queue, and wait till the stores hit the EPP. */
+        memset(priv->eq, 0, sizeof(lepp_queue_t));
+        mb();
+
+        return 0;
+}
+
+
+/*
+ * Prepare the "frags" info for the resulting LEPP command.
+ *
+ * If needed, flush the memory used by the frags.
+ */
+static unsigned int tile_net_tx_frags(lepp_frag_t *frags,
+                                      struct sk_buff *skb,
+                                      void *b_data, unsigned int b_len)
+{
+        unsigned int i, n = 0;
+
+        struct skb_shared_info *sh = skb_shinfo(skb);
+
+        phys_addr_t cpa;
+
+        if (b_len != 0) {
+
+                if (!hash_default)
+                        finv_buffer_remote(b_data, b_len, 0);
+
+                cpa = __pa(b_data);
+                frags[n].cpa_lo = cpa;
+                frags[n].cpa_hi = cpa >> 32;
+                frags[n].length = b_len;
+                frags[n].hash_for_home = hash_default;
+                n++;
+        }
+
+        for (i = 0; i < sh->nr_frags; i++) {
+
+                skb_frag_t *f = &sh->frags[i];
+                unsigned long pfn = page_to_pfn(f->page);
+
+                /* FIXME: Compute "hash_for_home" properly. */
+                /* ISSUE: The hypervisor checks CHIP_HAS_REV1_DMA_PACKETS(). */
+                int hash_for_home = hash_default;
+
+                /* FIXME: Hmmm. */
+                if (!hash_default) {
+                        void *va = pfn_to_kaddr(pfn) + f->page_offset;
+                        BUG_ON(PageHighMem(f->page));
+                        finv_buffer_remote(va, f->size, 0);
+                }
+
+                cpa = ((phys_addr_t)pfn << PAGE_SHIFT) + f->page_offset;
+                frags[n].cpa_lo = cpa;
+                frags[n].cpa_hi = cpa >> 32;
+                frags[n].length = f->size;
+                frags[n].hash_for_home = hash_for_home;
+                n++;
+        }
+
+        return n;
+}
+
+
+/*
+ * This function takes "skb", consisting of a header template and a
+ * payload, and hands it to LEPP, to emit as one or more segments,
+ * each consisting of a possibly modified header, plus a piece of the
+ * payload, via a process known as "tcp segmentation offload".
+ *
+ * Usually, "data" will contain the header template, of size "sh_len",
+ * and "sh->frags" will contain "skb->data_len" bytes of payload, and
+ * there will be "sh->gso_segs" segments.
+ *
+ * Sometimes, if "sendfile()" requires copying, we will be called with
+ * "data" containing the header and payload, with "frags" being empty.
+ *
+ * In theory, "sh->nr_frags" could be 3, but in practice, it seems
+ * that this will never actually happen.
+ *
+ * See "emulate_large_send_offload()" for some reference code, which
+ * does not handle checksumming.
+ *
+ * ISSUE: How do we make sure that high memory DMA does not migrate?
+ */
+static int tile_net_tx_tso(struct sk_buff *skb, struct net_device *dev)
+{
+        struct tile_net_priv *priv = netdev_priv(dev);
+        int my_cpu = smp_processor_id();
+        struct tile_net_cpu *info = priv->cpu[my_cpu];
+        struct tile_net_stats_t *stats = &info->stats;
+
+        struct skb_shared_info *sh = skb_shinfo(skb);
+
+        unsigned char *data = skb->data;
+
+        /* The ip header follows the ethernet header. */
+        struct iphdr *ih = ip_hdr(skb);
+        unsigned int ih_len = ih->ihl * 4;
+
+        /* Note that "nh == ih", by definition. */
+        unsigned char *nh = skb_network_header(skb);
+        unsigned int eh_len = nh - data;
+
+        /* The tcp header follows the ip header. */
+        struct tcphdr *th = (struct tcphdr *)(nh + ih_len);
+        unsigned int th_len = th->doff * 4;
+
+        /* The total number of header bytes. */
+        /* NOTE: This may be less than skb_headlen(skb). */
+        unsigned int sh_len = eh_len + ih_len + th_len;
+
+        /* The number of payload bytes at "skb->data + sh_len". */
+        /* This is non-zero for sendfile() without HIGHDMA. */
+        unsigned int b_len = skb_headlen(skb) - sh_len;
+
+        /* The total number of payload bytes. */
+        unsigned int d_len = b_len + skb->data_len;
+
+        /* The maximum payload size. */
+        unsigned int p_len = sh->gso_size;
+
+        /* The total number of segments. */
+        unsigned int num_segs = sh->gso_segs;
+
+        /* The temporary copy of the command. */
+        u32 cmd_body[(LEPP_MAX_CMD_SIZE + 3) / 4];
+        lepp_tso_cmd_t *cmd = (lepp_tso_cmd_t *)cmd_body;
+
+        /* Analyze the "frags". */
+        unsigned int num_frags =
+                tile_net_tx_frags(cmd->frags, skb, data + sh_len, b_len);
+
+        /* The size of the command, including frags and header. */
+        size_t cmd_size = LEPP_TSO_CMD_SIZE(num_frags, sh_len);
+
+        /* The command header. */
+        lepp_tso_cmd_t cmd_init = {
+                .tso = true,
+                .header_size = sh_len,
+                .ip_offset = eh_len,
+                .tcp_offset = eh_len + ih_len,
+                .payload_size = p_len,
+                .num_frags = num_frags,
+        };
+
+        unsigned long irqflags;
+
+        lepp_queue_t *eq = priv->eq;
+
+        struct sk_buff *olds[8];
+        unsigned int wanted = 8;
+        unsigned int i, nolds = 0;
+
+        unsigned int cmd_head, cmd_tail, cmd_next;
+        unsigned int comp_tail;
+
+
+        /* Paranoia. */
+        BUG_ON(skb->protocol != htons(ETH_P_IP));
+        BUG_ON(ih->protocol != IPPROTO_TCP);
+        BUG_ON(skb->ip_summed != CHECKSUM_PARTIAL);
+        BUG_ON(num_frags > LEPP_MAX_FRAGS);
+        /*--BUG_ON(num_segs != (d_len + (p_len - 1)) / p_len); */
+        BUG_ON(num_segs <= 1);
+
+
+        /* Finish preparing the command. */
+
+        /* Copy the command header. */
+        *cmd = cmd_init;
+
+        /* Copy the "header". */
+        memcpy(&cmd->frags[num_frags], data, sh_len);
+
+
+        /* Prefetch and wait, to minimize time spent holding the spinlock. */
+        prefetch_L1(&eq->comp_tail);
+        prefetch_L1(&eq->cmd_tail);
+        mb();
+
+
+        /* Enqueue the command. */
+
+        spin_lock_irqsave(&priv->eq_lock, irqflags);
+
+        /*
+         * Handle completions if needed to make room.
+         * HACK: Spin until there is sufficient room.
+         */
+        if (lepp_num_free_comp_slots(eq) == 0) {
+                nolds = tile_net_lepp_grab_comps(eq, olds, wanted, 0);
+                if (nolds == 0) {
+busy:
+                        spin_unlock_irqrestore(&priv->eq_lock, irqflags);
+                        return NETDEV_TX_BUSY;
+                }
+        }
+
+        cmd_head = eq->cmd_head;
+        cmd_tail = eq->cmd_tail;
+
+        /* Prepare to advance, detecting full queue. */
+        cmd_next = cmd_tail + cmd_size;
+        if (cmd_tail < cmd_head && cmd_next >= cmd_head)
+                goto busy;
+        if (cmd_next > LEPP_CMD_LIMIT) {
+                cmd_next = 0;
+                if (cmd_next == cmd_head)
+                        goto busy;
+        }
+
+        /* Copy the command. */
+        memcpy(&eq->cmds[cmd_tail], cmd, cmd_size);
+
+        /* Advance. */
+        cmd_tail = cmd_next;
+
+        /* Record "skb" for eventual freeing. */
+        comp_tail = eq->comp_tail;
+        eq->comps[comp_tail] = skb;
+        LEPP_QINC(comp_tail);
+        eq->comp_tail = comp_tail;
+
+        /* Flush before allowing LEPP to handle the command. */
+        /* ISSUE: Is this the optimal location for the flush? */
+        __insn_mf();
+
+        eq->cmd_tail = cmd_tail;
+
+        /* NOTE: Using "4" here is more efficient than "0" or "2", */
+        /* and, strangely, more efficient than pre-checking the number */
+        /* of available completions, and comparing it to 4. */
+        if (nolds == 0)
+                nolds = tile_net_lepp_grab_comps(eq, olds, wanted, 4);
+
+        spin_unlock_irqrestore(&priv->eq_lock, irqflags);
+
+        /* Handle completions. */
+        for (i = 0; i < nolds; i++)
+                kfree_skb(olds[i]);
+
+        /* Update stats. */
+        stats->tx_packets += num_segs;
+        stats->tx_bytes += (num_segs * sh_len) + d_len;
+
+        /* Make sure the egress timer is scheduled. */
+        tile_net_schedule_egress_timer(info);
+
+        return NETDEV_TX_OK;
+}
+
+
+/*
+ * Transmit a packet (called by the kernel via "hard_start_xmit" hook).
+ */
+static int tile_net_tx(struct sk_buff *skb, struct net_device *dev)
+{
+        struct tile_net_priv *priv = netdev_priv(dev);
+        int my_cpu = smp_processor_id();
+        struct tile_net_cpu *info = priv->cpu[my_cpu];
+        struct tile_net_stats_t *stats = &info->stats;
+
+        unsigned long irqflags;
+
+        struct skb_shared_info *sh = skb_shinfo(skb);
+
+        unsigned int len = skb->len;
+        unsigned char *data = skb->data;
+
+        unsigned int csum_start = skb_checksum_start_offset(skb);
+
+        lepp_frag_t frags[LEPP_MAX_FRAGS];
+
+        unsigned int num_frags;
+
+        lepp_queue_t *eq = priv->eq;
+
+        struct sk_buff *olds[8];
+        unsigned int wanted = 8;
+        unsigned int i, nolds = 0;
+
+        unsigned int cmd_size = sizeof(lepp_cmd_t);
+
+        unsigned int cmd_head, cmd_tail, cmd_next;
+        unsigned int comp_tail;
+
+        lepp_cmd_t cmds[LEPP_MAX_FRAGS];
+
+
+        /*
+         * This is paranoia, since we think that if the link doesn't come
+         * up, telling Linux we have no carrier will keep it from trying
+         * to transmit.  If it does, though, we can't execute this routine,
+         * since data structures we depend on aren't set up yet.
+         */
+        if (!info->registered)
+                return NETDEV_TX_BUSY;
+
+
+        /* Save the timestamp. */
+        dev->trans_start = jiffies;
+
+
+#ifdef TILE_NET_PARANOIA
+#if CHIP_HAS_CBOX_HOME_MAP()
+        if (hash_default) {
+                HV_PTE pte = *virt_to_pte(current->mm, (unsigned long)data);
+                if (hv_pte_get_mode(pte) != HV_PTE_MODE_CACHE_HASH_L3)
+                        panic("Non-HFH egress buffer! VA=%p Mode=%d PTE=%llx",
+                              data, hv_pte_get_mode(pte), hv_pte_val(pte));
+        }
+#endif
+#endif
+
+
+#ifdef TILE_NET_DUMP_PACKETS
+        /* ISSUE: Does not dump the "frags". */
+        dump_packet(data, skb_headlen(skb), "tx");
+#endif /* TILE_NET_DUMP_PACKETS */
+
+
+        if (sh->gso_size != 0)
+                return tile_net_tx_tso(skb, dev);
+
+
+        /* Prepare the commands. */
+
+        num_frags = tile_net_tx_frags(frags, skb, data, skb_headlen(skb));
+
+        for (i = 0; i < num_frags; i++) {
+
+                bool final = (i == num_frags - 1);
+
+                lepp_cmd_t cmd = {
+                        .cpa_lo = frags[i].cpa_lo,
+                        .cpa_hi = frags[i].cpa_hi,
+                        .length = frags[i].length,
+                        .hash_for_home = frags[i].hash_for_home,
+                        .send_completion = final,
+                        .end_of_packet = final
+                };
+
+                if (i == 0 && skb->ip_summed == CHECKSUM_PARTIAL) {
+                        cmd.compute_checksum = 1;
+                        cmd.checksum_data.bits.start_byte = csum_start;
+                        cmd.checksum_data.bits.count = len - csum_start;
+                        cmd.checksum_data.bits.destination_byte =
+                                csum_start + skb->csum_offset;
+                }
+
+                cmds[i] = cmd;
+        }
+
+
+        /* Prefetch and wait, to minimize time spent holding the spinlock. */
+        prefetch_L1(&eq->comp_tail);
+        prefetch_L1(&eq->cmd_tail);
+        mb();
+
+
+        /* Enqueue the commands. */
+
+        spin_lock_irqsave(&priv->eq_lock, irqflags);
+
+        /*
+         * Handle completions if needed to make room.
+         * HACK: Spin until there is sufficient room.
+         */
+        if (lepp_num_free_comp_slots(eq) == 0) {
+                nolds = tile_net_lepp_grab_comps(eq, olds, wanted, 0);
+                if (nolds == 0) {
+busy:
+                        spin_unlock_irqrestore(&priv->eq_lock, irqflags);
+                        return NETDEV_TX_BUSY;
+                }
+        }
+
+        cmd_head = eq->cmd_head;
+        cmd_tail = eq->cmd_tail;
+
+        /* Copy the commands, or fail. */
+        for (i = 0; i < num_frags; i++) {
+
+                /* Prepare to advance, detecting full queue. */
+                cmd_next = cmd_tail + cmd_size;
+                if (cmd_tail < cmd_head && cmd_next >= cmd_head)
+                        goto busy;
+                if (cmd_next > LEPP_CMD_LIMIT) {
+                        cmd_next = 0;
+                        if (cmd_next == cmd_head)
+                                goto busy;
+                }
+
+                /* Copy the command. */
+                *(lepp_cmd_t *)&eq->cmds[cmd_tail] = cmds[i];
+
+                /* Advance. */
+                cmd_tail = cmd_next;
+        }
+
+        /* Record "skb" for eventual freeing. */
+        comp_tail = eq->comp_tail;
+        eq->comps[comp_tail] = skb;
+        LEPP_QINC(comp_tail);
+        eq->comp_tail = comp_tail;
+
+        /* Flush before allowing LEPP to handle the command. */
+        /* ISSUE: Is this the optimal location for the flush? */
+        __insn_mf();
+
+        eq->cmd_tail = cmd_tail;
+
+        /* NOTE: Using "4" here is more efficient than "0" or "2", */
+        /* and, strangely, more efficient than pre-checking the number */
+        /* of available completions, and comparing it to 4. */
+        if (nolds == 0)
+                nolds = tile_net_lepp_grab_comps(eq, olds, wanted, 4);
+
+        spin_unlock_irqrestore(&priv->eq_lock, irqflags);
+
+        /* Handle completions. */
+        for (i = 0; i < nolds; i++)
+                kfree_skb(olds[i]);
+
+        /* HACK: Track "expanded" size for short packets (e.g. 42 < 60). */
+        stats->tx_packets++;
+        stats->tx_bytes += ((len >= ETH_ZLEN) ? len : ETH_ZLEN);
+
+        /* Make sure the egress timer is scheduled. */
+        tile_net_schedule_egress_timer(info);
+
+        return NETDEV_TX_OK;
+}
+
+
+/*
+ * Deal with a transmit timeout.
+ */
+static void tile_net_tx_timeout(struct net_device *dev)
+{
+        PDEBUG("tile_net_tx_timeout()\n");
+        PDEBUG("Transmit timeout at %ld, latency %ld\n", jiffies,
+               jiffies - dev->trans_start);
+
+        /* XXX: ISSUE: This doesn't seem useful for us. */
+        netif_wake_queue(dev);
+}
+
+
+/*
+ * Ioctl commands.
+ */
+static int tile_net_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
+{
+        return -EOPNOTSUPP;
+}
+
+
+/*
+ * Get System Network Statistics.
+ *
+ * Returns the address of the device statistics structure.
+ */
+static struct net_device_stats *tile_net_get_stats(struct net_device *dev)
+{
+        struct tile_net_priv *priv = netdev_priv(dev);
+        u32 rx_packets = 0;
+        u32 tx_packets = 0;
+        u32 rx_bytes = 0;
+        u32 tx_bytes = 0;
+        int i;
+
+        for_each_online_cpu(i) {
+                if (priv->cpu[i]) {
+                        rx_packets += priv->cpu[i]->stats.rx_packets;
+                        rx_bytes += priv->cpu[i]->stats.rx_bytes;
+                        tx_packets += priv->cpu[i]->stats.tx_packets;
+                        tx_bytes += priv->cpu[i]->stats.tx_bytes;
+                }
+        }
+
+        priv->stats.rx_packets = rx_packets;
+        priv->stats.rx_bytes = rx_bytes;
+        priv->stats.tx_packets = tx_packets;
+        priv->stats.tx_bytes = tx_bytes;
+
+        return &priv->stats;
+}
+
+
+/*
+ * Change the "mtu".
+ *
+ * The "change_mtu" method is usually not needed.
+ * If you need it, it must be like this.
+ */
+static int tile_net_change_mtu(struct net_device *dev, int new_mtu)
+{
+        PDEBUG("tile_net_change_mtu()\n");
+
+        /* Check ranges. */
+        if ((new_mtu < 68) || (new_mtu > 1500))
+                return -EINVAL;
+
+        /* Accept the value. */
+        dev->mtu = new_mtu;
+
+        return 0;
+}
+
+
+/*
+ * Change the Ethernet Address of the NIC.
+ *
+ * The hypervisor driver does not support changing MAC address.  However,
+ * the IPP does not do anything with the MAC address, so the address which
+ * gets used on outgoing packets, and which is accepted on incoming packets,
+ * is completely up to the NetIO program or kernel driver which is actually
+ * handling them.
+ *
+ * Returns 0 on success, negative on failure.
+ */
+static int tile_net_set_mac_address(struct net_device *dev, void *p)
+{
+        struct sockaddr *addr = p;
+
+        if (!is_valid_ether_addr(addr->sa_data))
+                return -EINVAL;
+
+        /* ISSUE: Note that "dev_addr" is now a pointer. */
+        memcpy(dev->dev_addr, addr->sa_data, dev->addr_len);
+
+        return 0;
+}
+
+
+/*
+ * Obtain the MAC address from the hypervisor.
+ * This must be done before opening the device.
+ */
+static int tile_net_get_mac(struct net_device *dev)
+{
+        struct tile_net_priv *priv = netdev_priv(dev);
+
+        char hv_dev_name[32];
+        int len;
+
+        __netio_getset_offset_t offset = { .word = NETIO_IPP_PARAM_OFF };
+
+        int ret;
+
+        /* For example, "xgbe0". */
+        strcpy(hv_dev_name, dev->name);
+        len = strlen(hv_dev_name);
+
+        /* For example, "xgbe/0". */
+        hv_dev_name[len] = hv_dev_name[len - 1];
+        hv_dev_name[len - 1] = '/';
+        len++;
+
+        /* For example, "xgbe/0/native_hash". */
+        strcpy(hv_dev_name + len, hash_default ? "/native_hash" : "/native");
+
+        /* Get the hypervisor handle for this device. */
+        priv->hv_devhdl = hv_dev_open((HV_VirtAddr)hv_dev_name, 0);
+        PDEBUG("hv_dev_open(%s) returned %d %p\n",
+               hv_dev_name, priv->hv_devhdl, &priv->hv_devhdl);
+        if (priv->hv_devhdl < 0) {
+                if (priv->hv_devhdl == HV_ENODEV)
+                        printk(KERN_DEBUG "Ignoring unconfigured device %s\n",
+                                 hv_dev_name);
+                else
+                        printk(KERN_DEBUG "hv_dev_open(%s) returned %d\n",
+                                 hv_dev_name, priv->hv_devhdl);
+                return -1;
+        }
+
+        /*
+         * Read the hardware address from the hypervisor.
+         * ISSUE: Note that "dev_addr" is now a pointer.
+         */
+        offset.bits.class = NETIO_PARAM;
+        offset.bits.addr = NETIO_PARAM_MAC;
+        ret = hv_dev_pread(priv->hv_devhdl, 0,
+                           (HV_VirtAddr)dev->dev_addr, dev->addr_len,
+                           offset.word);
+        PDEBUG("hv_dev_pread(NETIO_PARAM_MAC) returned %d\n", ret);
+        if (ret <= 0) {
+                printk(KERN_DEBUG "hv_dev_pread(NETIO_PARAM_MAC) %s failed\n",
+                       dev->name);
+                /*
+                 * Since the device is configured by the hypervisor but we
+                 * can't get its MAC address, we are most likely running
+                 * the simulator, so let's generate a random MAC address.
+                 */
+                random_ether_addr(dev->dev_addr);
+        }
+
+        return 0;
+}
+
+
+static struct net_device_ops tile_net_ops = {
+        .ndo_open = tile_net_open,
+        .ndo_stop = tile_net_stop,
+        .ndo_start_xmit = tile_net_tx,
+        .ndo_do_ioctl = tile_net_ioctl,
+        .ndo_get_stats = tile_net_get_stats,
+        .ndo_change_mtu = tile_net_change_mtu,
+        .ndo_tx_timeout = tile_net_tx_timeout,
+        .ndo_set_mac_address = tile_net_set_mac_address
+};
+
+
+/*
+ * The setup function.
+ *
+ * This uses ether_setup() to assign various fields in dev, including
+ * setting IFF_BROADCAST and IFF_MULTICAST, then sets some extra fields.
+ */
+static void tile_net_setup(struct net_device *dev)
+{
+        PDEBUG("tile_net_setup()\n");
+
+        ether_setup(dev);
+
+        dev->netdev_ops = &tile_net_ops;
+
+        dev->watchdog_timeo = TILE_NET_TIMEOUT;
+
+        /* We want lockless xmit. */
+        dev->features |= NETIF_F_LLTX;
+
+        /* We support hardware tx checksums. */
+        dev->features |= NETIF_F_HW_CSUM;
+
+        /* We support scatter/gather. */
+        dev->features |= NETIF_F_SG;
+
+        /* We support TSO. */
+        dev->features |= NETIF_F_TSO;
+
+#ifdef TILE_NET_GSO
+        /* We support GSO. */
+        dev->features |= NETIF_F_GSO;
+#endif
+
+        if (hash_default)
+                dev->features |= NETIF_F_HIGHDMA;
+
+        /* ISSUE: We should support NETIF_F_UFO. */
+
+        dev->tx_queue_len = TILE_NET_TX_QUEUE_LEN;
+
+        dev->mtu = TILE_NET_MTU;
+}
+
+
+/*
+ * Allocate the device structure, register the device, and obtain the
+ * MAC address from the hypervisor.
+ */
+static struct net_device *tile_net_dev_init(const char *name)
+{
+        int ret;
+        struct net_device *dev;
+        struct tile_net_priv *priv;
+
+        /*
+         * Allocate the device structure.  This allocates "priv", calls
+         * tile_net_setup(), and saves "name".  Normally, "name" is a
+         * template, instantiated by register_netdev(), but not for us.
+         */
+        dev = alloc_netdev(sizeof(*priv), name, tile_net_setup);
+        if (!dev) {
+                pr_err("alloc_netdev(%s) failed\n", name);
+                return NULL;
+        }
+
+        priv = netdev_priv(dev);
+
+        /* Initialize "priv". */
+
+        memset(priv, 0, sizeof(*priv));
+
+        /* Save "dev" for "tile_net_open_retry()". */
+        priv->dev = dev;
+
+        INIT_DELAYED_WORK(&priv->retry_work, tile_net_open_retry);
+
+        spin_lock_init(&priv->eq_lock);
+
+        /* Allocate "eq". */
+        priv->eq_pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, EQ_ORDER);
+        if (!priv->eq_pages) {
+                free_netdev(dev);
+                return NULL;
+        }
+        priv->eq = page_address(priv->eq_pages);
+
+        /* Register the network device. */
+        ret = register_netdev(dev);
+        if (ret) {
+                pr_err("register_netdev %s failed %d\n", dev->name, ret);
+                __free_pages(priv->eq_pages, EQ_ORDER);
+                free_netdev(dev);
+                return NULL;
+        }
+
+        /* Get the MAC address. */
+        ret = tile_net_get_mac(dev);
+        if (ret < 0) {
+                unregister_netdev(dev);
+                __free_pages(priv->eq_pages, EQ_ORDER);
+                free_netdev(dev);
+                return NULL;
+        }
+
+        return dev;
+}
+
+
+/*
+ * Module cleanup.
+ *
+ * FIXME: If compiled as a module, this module cannot be "unloaded",
+ * because the "ingress interrupt handler" is registered permanently.
+ */
+static void tile_net_cleanup(void)
+{
+        int i;
+
+        for (i = 0; i < TILE_NET_DEVS; i++) {
+                if (tile_net_devs[i]) {
+                        struct net_device *dev = tile_net_devs[i];
+                        struct tile_net_priv *priv = netdev_priv(dev);
+                        unregister_netdev(dev);
+                        finv_buffer_remote(priv->eq, EQ_SIZE, 0);
+                        __free_pages(priv->eq_pages, EQ_ORDER);
+                        free_netdev(dev);
+                }
+        }
+}
+
+
+/*
+ * Module initialization.
+ */
+static int tile_net_init_module(void)
+{
+        pr_info("Tilera IPP Net Driver\n");
+
+        tile_net_devs[0] = tile_net_dev_init("xgbe0");
+        tile_net_devs[1] = tile_net_dev_init("xgbe1");
+        tile_net_devs[2] = tile_net_dev_init("gbe0");
+        tile_net_devs[3] = tile_net_dev_init("gbe1");
+
+        return 0;
+}
+
+
+module_init(tile_net_init_module);
+module_exit(tile_net_cleanup);
+
+
+#ifndef MODULE
+
+/*
+ * The "network_cpus" boot argument specifies the cpus that are dedicated
+ * to handle ingress packets.
+ *
+ * The parameter should be in the form "network_cpus=m-n[,x-y]", where
+ * m, n, x, y are integer numbers that represent the cpus that can be
+ * neither a dedicated cpu nor a dataplane cpu.
+ */
+static int __init network_cpus_setup(char *str)
+{
+        int rc = cpulist_parse_crop(str, &network_cpus_map);
+        if (rc != 0) {
+                pr_warning("network_cpus=%s: malformed cpu list\n",
+                       str);
+        } else {
+
+                /* Remove dedicated cpus. */
+                cpumask_and(&network_cpus_map, &network_cpus_map,
+                            cpu_possible_mask);
+
+
+                if (cpumask_empty(&network_cpus_map)) {
+                        pr_warning("Ignoring network_cpus='%s'.\n",
+                               str);
+                } else {
+                        char buf[1024];
+                        cpulist_scnprintf(buf, sizeof(buf), &network_cpus_map);
+                        pr_info("Linux network CPUs: %s\n", buf);
+                        network_cpus_used = true;
+                }
+        }
+
+        return 0;
+}
+__setup("network_cpus=", network_cpus_setup);
+
+#endif