xen: Add xen_create_contiguous_region

A memory region must be physically contiguous in order to be accessed
through DMA.  This patch adds xen_create_contiguous_region, which
ensures a region of contiguous virtual memory is also physically
contiguous.

Based on Stephen Tweedie's port of the 2.6.18-xen version.

Remove contiguous_bitmap[] as it's no longer needed.

Ported from linux-2.6.18-xen.hg 707:e410857fd83c

[ Impact: add Xen-internal API to make pages phys-contig ]

Signed-off-by: Alex Nixon <alex.nixon@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 201 insertions, 0 deletions

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 9e0d82fc21e4..eb51402dd99a 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -53,6 +53,7 @@
 #include <asm/paravirt.h>
 #include <asm/e820.h>
 #include <asm/linkage.h>
+#include <asm/page.h>
 
 #include <asm/xen/hypercall.h>
 #include <asm/xen/hypervisor.h>
@@ -2027,6 +2028,206 @@ void __init xen_init_mmu_ops(void)
         pv_mmu_ops = xen_mmu_ops;
 }
 
+/* Protected by xen_reservation_lock. */
+#define MAX_CONTIG_ORDER 9 /* 2MB */
+static unsigned long discontig_frames[1<<MAX_CONTIG_ORDER];
+
+#define VOID_PTE (mfn_pte(0, __pgprot(0)))
+static void xen_zap_pfn_range(unsigned long vaddr, unsigned int order,
+                                unsigned long *in_frames,
+                                unsigned long *out_frames)
+{
+        int i;
+        struct multicall_space mcs;
+
+        xen_mc_batch();
+        for (i = 0; i < (1UL<<order); i++, vaddr += PAGE_SIZE) {
+                mcs = __xen_mc_entry(0);
+
+                if (in_frames)
+                        in_frames[i] = virt_to_mfn(vaddr);
+
+                MULTI_update_va_mapping(mcs.mc, vaddr, VOID_PTE, 0);
+                set_phys_to_machine(virt_to_pfn(vaddr), INVALID_P2M_ENTRY);
+
+                if (out_frames)
+                        out_frames[i] = virt_to_pfn(vaddr);
+        }
+        xen_mc_issue(0);
+}
+
+/*
+ * Update the pfn-to-mfn mappings for a virtual address range, either to
+ * point to an array of mfns, or contiguously from a single starting
+ * mfn.
+ */
+static void xen_remap_exchanged_ptes(unsigned long vaddr, int order,
+                                     unsigned long *mfns,
+                                     unsigned long first_mfn)
+{
+        unsigned i, limit;
+        unsigned long mfn;
+
+        xen_mc_batch();
+
+        limit = 1u << order;
+        for (i = 0; i < limit; i++, vaddr += PAGE_SIZE) {
+                struct multicall_space mcs;
+                unsigned flags;
+
+                mcs = __xen_mc_entry(0);
+                if (mfns)
+                        mfn = mfns[i];
+                else
+                        mfn = first_mfn + i;
+
+                if (i < (limit - 1))
+                        flags = 0;
+                else {
+                        if (order == 0)
+                                flags = UVMF_INVLPG | UVMF_ALL;
+                        else
+                                flags = UVMF_TLB_FLUSH | UVMF_ALL;
+                }
+
+                MULTI_update_va_mapping(mcs.mc, vaddr,
+                                mfn_pte(mfn, PAGE_KERNEL), flags);
+
+                set_phys_to_machine(virt_to_pfn(vaddr), mfn);
+        }
+
+        xen_mc_issue(0);
+}
+
+/*
+ * Perform the hypercall to exchange a region of our pfns to point to
+ * memory with the required contiguous alignment.  Takes the pfns as
+ * input, and populates mfns as output.
+ *
+ * Returns a success code indicating whether the hypervisor was able to
+ * satisfy the request or not.
+ */
+static int xen_exchange_memory(unsigned long extents_in, unsigned int order_in,
+                               unsigned long *pfns_in,
+                               unsigned long extents_out,
+                               unsigned int order_out,
+                               unsigned long *mfns_out,
+                               unsigned int address_bits)
+{
+        long rc;
+        int success;
+
+        struct xen_memory_exchange exchange = {
+                .in = {
+                        .nr_extents   = extents_in,
+                        .extent_order = order_in,
+                        .extent_start = pfns_in,
+                        .domid        = DOMID_SELF
+                },
+                .out = {
+                        .nr_extents   = extents_out,
+                        .extent_order = order_out,
+                        .extent_start = mfns_out,
+                        .address_bits = address_bits,
+                        .domid        = DOMID_SELF
+                }
+        };
+
+        BUG_ON(extents_in << order_in != extents_out << order_out);
+
+        rc = HYPERVISOR_memory_op(XENMEM_exchange, &exchange);
+        success = (exchange.nr_exchanged == extents_in);
+
+        BUG_ON(!success && ((exchange.nr_exchanged != 0) || (rc == 0)));
+        BUG_ON(success && (rc != 0));
+
+        return success;
+}
+
+int xen_create_contiguous_region(unsigned long vstart, unsigned int order,
+                                 unsigned int address_bits)
+{
+        unsigned long *in_frames = discontig_frames, out_frame;
+        unsigned long  flags;
+        int            success;
+
+        /*
+         * Currently an auto-translated guest will not perform I/O, nor will
+         * it require PAE page directories below 4GB. Therefore any calls to
+         * this function are redundant and can be ignored.
+         */
+
+        if (xen_feature(XENFEAT_auto_translated_physmap))
+                return 0;
+
+        if (unlikely(order > MAX_CONTIG_ORDER))
+                return -ENOMEM;
+
+        memset((void *) vstart, 0, PAGE_SIZE << order);
+
+        vm_unmap_aliases();
+
+        spin_lock_irqsave(&xen_reservation_lock, flags);
+
+        /* 1. Zap current PTEs, remembering MFNs. */
+        xen_zap_pfn_range(vstart, order, in_frames, NULL);
+
+        /* 2. Get a new contiguous memory extent. */
+        out_frame = virt_to_pfn(vstart);
+        success = xen_exchange_memory(1UL << order, 0, in_frames,
+                                      1, order, &out_frame,
+                                      address_bits);
+
+        /* 3. Map the new extent in place of old pages. */
+        if (success)
+                xen_remap_exchanged_ptes(vstart, order, NULL, out_frame);
+        else
+                xen_remap_exchanged_ptes(vstart, order, in_frames, 0);
+
+        spin_unlock_irqrestore(&xen_reservation_lock, flags);
+
+        return success ? 0 : -ENOMEM;
+}
+EXPORT_SYMBOL_GPL(xen_create_contiguous_region);
+
+void xen_destroy_contiguous_region(unsigned long vstart, unsigned int order)
+{
+        unsigned long *out_frames = discontig_frames, in_frame;
+        unsigned long  flags;
+        int success;
+
+        if (xen_feature(XENFEAT_auto_translated_physmap))
+                return;
+
+        if (unlikely(order > MAX_CONTIG_ORDER))
+                return;
+
+        memset((void *) vstart, 0, PAGE_SIZE << order);
+
+        vm_unmap_aliases();
+
+        spin_lock_irqsave(&xen_reservation_lock, flags);
+
+        /* 1. Find start MFN of contiguous extent. */
+        in_frame = virt_to_mfn(vstart);
+
+        /* 2. Zap current PTEs. */
+        xen_zap_pfn_range(vstart, order, NULL, out_frames);
+
+        /* 3. Do the exchange for non-contiguous MFNs. */
+        success = xen_exchange_memory(1, order, &in_frame, 1UL << order,
+                                        0, out_frames, 0);
+
+        /* 4. Map new pages in place of old pages. */
+        if (success)
+                xen_remap_exchanged_ptes(vstart, order, out_frames, 0);
+        else
+                xen_remap_exchanged_ptes(vstart, order, NULL, in_frame);
+
+        spin_unlock_irqrestore(&xen_reservation_lock, flags);
+}
+EXPORT_SYMBOL_GPL(xen_destroy_contiguous_region);
+
 #ifdef CONFIG_XEN_DEBUG_FS
 
 static struct dentry *d_mmu_debug;