GRU Driver: kernel services provide by driver

This file contains functions for handling services provided to other
kernel modules that use the GRU.

Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 679 insertions, 0 deletions

diff --git a/drivers/misc/sgi-gru/grukservices.c b/drivers/misc/sgi-gru/grukservices.c
new file mode 100644
index 000000000000..234d165fb11e
--- /dev/null
+++ b/drivers/misc/sgi-gru/grukservices.c
@@ -0,0 +1,679 @@
+/*
+ * SN Platform GRU Driver
+ *
+ *              KERNEL SERVICES THAT USE THE GRU
+ *
+ *  Copyright (c) 2008 Silicon Graphics, Inc.  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; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  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.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
+#include <linux/smp_lock.h>
+#include <linux/spinlock.h>
+#include <linux/device.h>
+#include <linux/miscdevice.h>
+#include <linux/proc_fs.h>
+#include <linux/interrupt.h>
+#include <linux/uaccess.h>
+#include "gru.h"
+#include "grulib.h"
+#include "grutables.h"
+#include "grukservices.h"
+#include "gru_instructions.h"
+#include <asm/uv/uv_hub.h>
+
+/*
+ * Kernel GRU Usage
+ *
+ * The following is an interim algorithm for management of kernel GRU
+ * resources. This will likely be replaced when we better understand the
+ * kernel/user requirements.
+ *
+ * At boot time, the kernel permanently reserves a fixed number of
+ * CBRs/DSRs for each cpu to use. The resources are all taken from
+ * the GRU chiplet 1 on the blade. This leaves the full set of resources
+ * of chiplet 0 available to be allocated to a single user.
+ */
+
+/* Blade percpu resources PERMANENTLY reserved for kernel use */
+#define GRU_NUM_KERNEL_CBR      1
+#define GRU_NUM_KERNEL_DSR_BYTES 256
+#define KERNEL_CTXNUM           15
+
+/* GRU instruction attributes for all instructions */
+#define IMA                     IMA_CB_DELAY
+
+/* GRU cacheline size is always 64 bytes - even on arches with 128 byte lines */
+#define __gru_cacheline_aligned__                               \
+        __attribute__((__aligned__(GRU_CACHE_LINE_BYTES)))
+
+#define MAGIC   0x1234567887654321UL
+
+/* Default retry count for GRU errors on kernel instructions */
+#define EXCEPTION_RETRY_LIMIT   3
+
+/* Status of message queue sections */
+#define MQS_EMPTY               0
+#define MQS_FULL                1
+#define MQS_NOOP                2
+
+/*----------------- RESOURCE MANAGEMENT -------------------------------------*/
+/* optimized for x86_64 */
+struct message_queue {
+        union gru_mesqhead      head __gru_cacheline_aligned__; /* CL 0 */
+        int                     qlines;                         /* DW 1 */
+        long                    hstatus[2];
+        void                    *next __gru_cacheline_aligned__;/* CL 1 */
+        void                    *limit;
+        void                    *start;
+        void                    *start2;
+        char                    data ____cacheline_aligned;     /* CL 2 */
+};
+
+/* First word in every message - used by mesq interface */
+struct message_header {
+        char    present;
+        char    present2;
+        char    lines;
+        char    fill;
+};
+
+#define QLINES(mq)      ((mq) + offsetof(struct message_queue, qlines))
+#define HSTATUS(mq, h)  ((mq) + offsetof(struct message_queue, hstatus[h]))
+
+static int gru_get_cpu_resources(int dsr_bytes, void **cb, void **dsr)
+{
+        struct gru_blade_state *bs;
+        int lcpu;
+
+        BUG_ON(dsr_bytes > GRU_NUM_KERNEL_DSR_BYTES);
+        preempt_disable();
+        bs = gru_base[uv_numa_blade_id()];
+        lcpu = uv_blade_processor_id();
+        *cb = bs->kernel_cb + lcpu * GRU_HANDLE_STRIDE;
+        *dsr = bs->kernel_dsr + lcpu * GRU_NUM_KERNEL_DSR_BYTES;
+        return 0;
+}
+
+static void gru_free_cpu_resources(void *cb, void *dsr)
+{
+        preempt_enable();
+}
+
+int gru_get_cb_exception_detail(void *cb,
+                struct control_block_extended_exc_detail *excdet)
+{
+        struct gru_control_block_extended *cbe;
+
+        cbe = get_cbe(GRUBASE(cb), get_cb_number(cb));
+        excdet->opc = cbe->opccpy;
+        excdet->exopc = cbe->exopccpy;
+        excdet->ecause = cbe->ecause;
+        excdet->exceptdet0 = cbe->idef1upd;
+        excdet->exceptdet1 = cbe->idef3upd;
+        return 0;
+}
+
+char *gru_get_cb_exception_detail_str(int ret, void *cb,
+                                      char *buf, int size)
+{
+        struct gru_control_block_status *gen = (void *)cb;
+        struct control_block_extended_exc_detail excdet;
+
+        if (ret > 0 && gen->istatus == CBS_EXCEPTION) {
+                gru_get_cb_exception_detail(cb, &excdet);
+                snprintf(buf, size,
+                        "GRU exception: cb %p, opc %d, exopc %d, ecause 0x%x,"
+                        "excdet0 0x%lx, excdet1 0x%x",
+                        gen, excdet.opc, excdet.exopc, excdet.ecause,
+                        excdet.exceptdet0, excdet.exceptdet1);
+        } else {
+                snprintf(buf, size, "No exception");
+        }
+        return buf;
+}
+
+static int gru_wait_idle_or_exception(struct gru_control_block_status *gen)
+{
+        while (gen->istatus >= CBS_ACTIVE) {
+                cpu_relax();
+                barrier();
+        }
+        return gen->istatus;
+}
+
+static int gru_retry_exception(void *cb)
+{
+        struct gru_control_block_status *gen = (void *)cb;
+        struct control_block_extended_exc_detail excdet;
+        int retry = EXCEPTION_RETRY_LIMIT;
+
+        while (1)  {
+                if (gru_get_cb_message_queue_substatus(cb))
+                        break;
+                if (gru_wait_idle_or_exception(gen) == CBS_IDLE)
+                        return CBS_IDLE;
+
+                gru_get_cb_exception_detail(cb, &excdet);
+                if (excdet.ecause & ~EXCEPTION_RETRY_BITS)
+                        break;
+                if (retry-- == 0)
+                        break;
+                gen->icmd = 1;
+                gru_flush_cache(gen);
+        }
+        return CBS_EXCEPTION;
+}
+
+int gru_check_status_proc(void *cb)
+{
+        struct gru_control_block_status *gen = (void *)cb;
+        int ret;
+
+        ret = gen->istatus;
+        if (ret != CBS_EXCEPTION)
+                return ret;
+        return gru_retry_exception(cb);
+
+}
+
+int gru_wait_proc(void *cb)
+{
+        struct gru_control_block_status *gen = (void *)cb;
+        int ret;
+
+        ret = gru_wait_idle_or_exception(gen);
+        if (ret == CBS_EXCEPTION)
+                ret = gru_retry_exception(cb);
+
+        return ret;
+}
+
+void gru_abort(int ret, void *cb, char *str)
+{
+        char buf[GRU_EXC_STR_SIZE];
+
+        panic("GRU FATAL ERROR: %s - %s\n", str,
+              gru_get_cb_exception_detail_str(ret, cb, buf, sizeof(buf)));
+}
+
+void gru_wait_abort_proc(void *cb)
+{
+        int ret;
+
+        ret = gru_wait_proc(cb);
+        if (ret)
+                gru_abort(ret, cb, "gru_wait_abort");
+}
+
+
+/*------------------------------ MESSAGE QUEUES -----------------------------*/
+
+/* Internal status . These are NOT returned to the user. */
+#define MQIE_AGAIN              -1      /* try again */
+
+
+/*
+ * Save/restore the "present" flag that is in the second line of 2-line
+ * messages
+ */
+static inline int get_present2(void *p)
+{
+        struct message_header *mhdr = p + GRU_CACHE_LINE_BYTES;
+        return mhdr->present;
+}
+
+static inline void restore_present2(void *p, int val)
+{
+        struct message_header *mhdr = p + GRU_CACHE_LINE_BYTES;
+        mhdr->present = val;
+}
+
+/*
+ * Create a message queue.
+ *      qlines - message queue size in cache lines. Includes 2-line header.
+ */
+int gru_create_message_queue(void *p, unsigned int bytes)
+{
+        struct message_queue *mq = p;
+        unsigned int qlines;
+
+        qlines = bytes / GRU_CACHE_LINE_BYTES - 2;
+        memset(mq, 0, bytes);
+        mq->start = &mq->data;
+        mq->start2 = &mq->data + (qlines / 2 - 1) * GRU_CACHE_LINE_BYTES;
+        mq->next = &mq->data;
+        mq->limit = &mq->data + (qlines - 2) * GRU_CACHE_LINE_BYTES;
+        mq->qlines = qlines;
+        mq->hstatus[0] = 0;
+        mq->hstatus[1] = 1;
+        mq->head = gru_mesq_head(2, qlines / 2 + 1);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(gru_create_message_queue);
+
+/*
+ * Send a NOOP message to a message queue
+ *      Returns:
+ *               0 - if queue is full after the send. This is the normal case
+ *                   but various races can change this.
+ *              -1 - if mesq sent successfully but queue not full
+ *              >0 - unexpected error. MQE_xxx returned
+ */
+static int send_noop_message(void *cb,
+                                unsigned long mq, void *mesg)
+{
+        const struct message_header noop_header = {
+                                        .present = MQS_NOOP, .lines = 1};
+        unsigned long m;
+        int substatus, ret;
+        struct message_header save_mhdr, *mhdr = mesg;
+
+        STAT(mesq_noop);
+        save_mhdr = *mhdr;
+        *mhdr = noop_header;
+        gru_mesq(cb, mq, gru_get_tri(mhdr), 1, IMA);
+        ret = gru_wait(cb);
+
+        if (ret) {
+                substatus = gru_get_cb_message_queue_substatus(cb);
+                switch (substatus) {
+                case CBSS_NO_ERROR:
+                        STAT(mesq_noop_unexpected_error);
+                        ret = MQE_UNEXPECTED_CB_ERR;
+                        break;
+                case CBSS_LB_OVERFLOWED:
+                        STAT(mesq_noop_lb_overflow);
+                        ret = MQE_CONGESTION;
+                        break;
+                case CBSS_QLIMIT_REACHED:
+                        STAT(mesq_noop_qlimit_reached);
+                        ret = 0;
+                        break;
+                case CBSS_AMO_NACKED:
+                        STAT(mesq_noop_amo_nacked);
+                        ret = MQE_CONGESTION;
+                        break;
+                case CBSS_PUT_NACKED:
+                        STAT(mesq_noop_put_nacked);
+                        m = mq + (gru_get_amo_value_head(cb) << 6);
+                        gru_vstore(cb, m, gru_get_tri(mesg), XTYPE_CL, 1, 1,
+                                                IMA);
+                        if (gru_wait(cb) == CBS_IDLE)
+                                ret = MQIE_AGAIN;
+                        else
+                                ret = MQE_UNEXPECTED_CB_ERR;
+                        break;
+                case CBSS_PAGE_OVERFLOW:
+                default:
+                        BUG();
+                }
+        }
+        *mhdr = save_mhdr;
+        return ret;
+}
+
+/*
+ * Handle a gru_mesq full.
+ */
+static int send_message_queue_full(void *cb,
+                           unsigned long mq, void *mesg, int lines)
+{
+        union gru_mesqhead mqh;
+        unsigned int limit, head;
+        unsigned long avalue;
+        int half, qlines, save;
+
+        /* Determine if switching to first/second half of q */
+        avalue = gru_get_amo_value(cb);
+        head = gru_get_amo_value_head(cb);
+        limit = gru_get_amo_value_limit(cb);
+
+        /*
+         * Fetch "qlines" from the queue header. Since the queue may be
+         * in memory that can't be accessed using socket addresses, use
+         * the GRU to access the data. Use DSR space from the message.
+         */
+        save = *(int *)mesg;
+        gru_vload(cb, QLINES(mq), gru_get_tri(mesg), XTYPE_W, 1, 1, IMA);
+        if (gru_wait(cb) != CBS_IDLE)
+                goto cberr;
+        qlines = *(int *)mesg;
+        *(int *)mesg = save;
+        half = (limit != qlines);
+
+        if (half)
+                mqh = gru_mesq_head(qlines / 2 + 1, qlines);
+        else
+                mqh = gru_mesq_head(2, qlines / 2 + 1);
+
+        /* Try to get lock for switching head pointer */
+        gru_gamir(cb, EOP_IR_CLR, HSTATUS(mq, half), XTYPE_DW, IMA);
+        if (gru_wait(cb) != CBS_IDLE)
+                goto cberr;
+        if (!gru_get_amo_value(cb)) {
+                STAT(mesq_qf_locked);
+                return MQE_QUEUE_FULL;
+        }
+
+        /* Got the lock. Send optional NOP if queue not full, */
+        if (head != limit) {
+                if (send_noop_message(cb, mq, mesg)) {
+                        gru_gamir(cb, EOP_IR_INC, HSTATUS(mq, half),
+                                        XTYPE_DW, IMA);
+                        if (gru_wait(cb) != CBS_IDLE)
+                                goto cberr;
+                        STAT(mesq_qf_noop_not_full);
+                        return MQIE_AGAIN;
+                }
+                avalue++;
+        }
+
+        /* Then flip queuehead to other half of queue. */
+        gru_gamer(cb, EOP_ERR_CSWAP, mq, XTYPE_DW, mqh.val, avalue, IMA);
+        if (gru_wait(cb) != CBS_IDLE)
+                goto cberr;
+
+        /* If not successfully in swapping queue head, clear the hstatus lock */
+        if (gru_get_amo_value(cb) != avalue) {
+                STAT(mesq_qf_switch_head_failed);
+                gru_gamir(cb, EOP_IR_INC, HSTATUS(mq, half), XTYPE_DW, IMA);
+                if (gru_wait(cb) != CBS_IDLE)
+                        goto cberr;
+        }
+        return MQIE_AGAIN;
+cberr:
+        STAT(mesq_qf_unexpected_error);
+        return MQE_UNEXPECTED_CB_ERR;
+}
+
+
+/*
+ * Handle a gru_mesq failure. Some of these failures are software recoverable
+ * or retryable.
+ */
+static int send_message_failure(void *cb,
+                                unsigned long mq,
+                                void *mesg,
+                                int lines)
+{
+        int substatus, ret = 0;
+        unsigned long m;
+
+        substatus = gru_get_cb_message_queue_substatus(cb);
+        switch (substatus) {
+        case CBSS_NO_ERROR:
+                STAT(mesq_send_unexpected_error);
+                ret = MQE_UNEXPECTED_CB_ERR;
+                break;
+        case CBSS_LB_OVERFLOWED:
+                STAT(mesq_send_lb_overflow);
+                ret = MQE_CONGESTION;
+                break;
+        case CBSS_QLIMIT_REACHED:
+                STAT(mesq_send_qlimit_reached);
+                ret = send_message_queue_full(cb, mq, mesg, lines);
+                break;
+        case CBSS_AMO_NACKED:
+                STAT(mesq_send_amo_nacked);
+                ret = MQE_CONGESTION;
+                break;
+        case CBSS_PUT_NACKED:
+                STAT(mesq_send_put_nacked);
+                m =mq + (gru_get_amo_value_head(cb) << 6);
+                gru_vstore(cb, m, gru_get_tri(mesg), XTYPE_CL, lines, 1, IMA);
+                if (gru_wait(cb) == CBS_IDLE)
+                        ret = MQE_OK;
+                else
+                        ret = MQE_UNEXPECTED_CB_ERR;
+                break;
+        default:
+                BUG();
+        }
+        return ret;
+}
+
+/*
+ * Send a message to a message queue
+ *      cb      GRU control block to use to send message
+ *      mq      message queue
+ *      mesg    message. ust be vaddr within a GSEG
+ *      bytes   message size (<= 2 CL)
+ */
+int gru_send_message_gpa(unsigned long mq, void *mesg, unsigned int bytes)
+{
+        struct message_header *mhdr;
+        void *cb;
+        void *dsr;
+        int istatus, clines, ret;
+
+        STAT(mesq_send);
+        BUG_ON(bytes < sizeof(int) || bytes > 2 * GRU_CACHE_LINE_BYTES);
+
+        clines = (bytes + GRU_CACHE_LINE_BYTES - 1) / GRU_CACHE_LINE_BYTES;
+        if (gru_get_cpu_resources(bytes, &cb, &dsr))
+                return MQE_BUG_NO_RESOURCES;
+        memcpy(dsr, mesg, bytes);
+        mhdr = dsr;
+        mhdr->present = MQS_FULL;
+        mhdr->lines = clines;
+        if (clines == 2) {
+                mhdr->present2 = get_present2(mhdr);
+                restore_present2(mhdr, MQS_FULL);
+        }
+
+        do {
+                ret = MQE_OK;
+                gru_mesq(cb, mq, gru_get_tri(mhdr), clines, IMA);
+                istatus = gru_wait(cb);
+                if (istatus != CBS_IDLE)
+                        ret = send_message_failure(cb, mq, dsr, clines);
+        } while (ret == MQIE_AGAIN);
+        gru_free_cpu_resources(cb, dsr);
+
+        if (ret)
+                STAT(mesq_send_failed);
+        return ret;
+}
+EXPORT_SYMBOL_GPL(gru_send_message_gpa);
+
+/*
+ * Advance the receive pointer for the queue to the next message.
+ */
+void gru_free_message(void *rmq, void *mesg)
+{
+        struct message_queue *mq = rmq;
+        struct message_header *mhdr = mq->next;
+        void *next, *pnext;
+        int half = -1;
+        int lines = mhdr->lines;
+
+        if (lines == 2)
+                restore_present2(mhdr, MQS_EMPTY);
+        mhdr->present = MQS_EMPTY;
+
+        pnext = mq->next;
+        next = pnext + GRU_CACHE_LINE_BYTES * lines;
+        if (next == mq->limit) {
+                next = mq->start;
+                half = 1;
+        } else if (pnext < mq->start2 && next >= mq->start2) {
+                half = 0;
+        }
+
+        if (half >= 0)
+                mq->hstatus[half] = 1;
+        mq->next = next;
+}
+EXPORT_SYMBOL_GPL(gru_free_message);
+
+/*
+ * Get next message from message queue. Return NULL if no message
+ * present. User must call next_message() to move to next message.
+ *      rmq     message queue
+ */
+void *gru_get_next_message(void *rmq)
+{
+        struct message_queue *mq = rmq;
+        struct message_header *mhdr = mq->next;
+        int present = mhdr->present;
+
+        /* skip NOOP messages */
+        STAT(mesq_receive);
+        while (present == MQS_NOOP) {
+                gru_free_message(rmq, mhdr);
+                mhdr = mq->next;
+                present = mhdr->present;
+        }
+
+        /* Wait for both halves of 2 line messages */
+        if (present == MQS_FULL && mhdr->lines == 2 &&
+                                get_present2(mhdr) == MQS_EMPTY)
+                present = MQS_EMPTY;
+
+        if (!present) {
+                STAT(mesq_receive_none);
+                return NULL;
+        }
+
+        if (mhdr->lines == 2)
+                restore_present2(mhdr, mhdr->present2);
+
+        return mhdr;
+}
+EXPORT_SYMBOL_GPL(gru_get_next_message);
+
+/* ---------------------- GRU DATA COPY FUNCTIONS ---------------------------*/
+
+/*
+ * Copy a block of data using the GRU resources
+ */
+int gru_copy_gpa(unsigned long dest_gpa, unsigned long src_gpa,
+                                unsigned int bytes)
+{
+        void *cb;
+        void *dsr;
+        int ret;
+
+        STAT(copy_gpa);
+        if (gru_get_cpu_resources(GRU_NUM_KERNEL_DSR_BYTES, &cb, &dsr))
+                return MQE_BUG_NO_RESOURCES;
+        gru_bcopy(cb, src_gpa, dest_gpa, gru_get_tri(dsr),
+                  XTYPE_B, bytes, GRU_NUM_KERNEL_DSR_BYTES, IMA);
+        ret = gru_wait(cb);
+        gru_free_cpu_resources(cb, dsr);
+        return ret;
+}
+EXPORT_SYMBOL_GPL(gru_copy_gpa);
+
+/* ------------------- KERNEL QUICKTESTS RUN AT STARTUP ----------------*/
+/*      Temp - will delete after we gain confidence in the GRU          */
+static __cacheline_aligned unsigned long word0;
+static __cacheline_aligned unsigned long word1;
+
+static int quicktest(struct gru_state *gru)
+{
+        void *cb;
+        void *ds;
+        unsigned long *p;
+
+        cb = get_gseg_base_address_cb(gru->gs_gru_base_vaddr, KERNEL_CTXNUM, 0);
+        ds = get_gseg_base_address_ds(gru->gs_gru_base_vaddr, KERNEL_CTXNUM, 0);
+        p = ds;
+        word0 = MAGIC;
+
+        gru_vload(cb, uv_gpa(&word0), 0, XTYPE_DW, 1, 1, IMA);
+        if (gru_wait(cb) != CBS_IDLE)
+                BUG();
+
+        if (*(unsigned long *)ds != MAGIC)
+                BUG();
+        gru_vstore(cb, uv_gpa(&word1), 0, XTYPE_DW, 1, 1, IMA);
+        if (gru_wait(cb) != CBS_IDLE)
+                BUG();
+
+        if (word0 != word1 || word0 != MAGIC) {
+                printk
+                    ("GRU quicktest err: gru %d, found 0x%lx, expected 0x%lx\n",
+                     gru->gs_gid, word1, MAGIC);
+                BUG();          /* ZZZ should not be fatal */
+        }
+
+        return 0;
+}
+
+
+int gru_kservices_init(struct gru_state *gru)
+{
+        struct gru_blade_state *bs;
+        struct gru_context_configuration_handle *cch;
+        unsigned long cbr_map, dsr_map;
+        int err, num, cpus_possible;
+
+        /*
+         * Currently, resources are reserved ONLY on the second chiplet
+         * on each blade. This leaves ALL resources on chiplet 0 available
+         * for user code.
+         */
+        bs = gru->gs_blade;
+        if (gru != &bs->bs_grus[1])
+                return 0;
+
+        cpus_possible = uv_blade_nr_possible_cpus(gru->gs_blade_id);
+
+        num = GRU_NUM_KERNEL_CBR * cpus_possible;
+        cbr_map = reserve_gru_cb_resources(gru, GRU_CB_COUNT_TO_AU(num), NULL);
+        gru->gs_reserved_cbrs += num;
+
+        num = GRU_NUM_KERNEL_DSR_BYTES * cpus_possible;
+        dsr_map = reserve_gru_ds_resources(gru, GRU_DS_BYTES_TO_AU(num), NULL);
+        gru->gs_reserved_dsr_bytes += num;
+
+        gru->gs_active_contexts++;
+        __set_bit(KERNEL_CTXNUM, &gru->gs_context_map);
+        cch = get_cch(gru->gs_gru_base_vaddr, KERNEL_CTXNUM);
+
+        bs->kernel_cb = get_gseg_base_address_cb(gru->gs_gru_base_vaddr,
+                                        KERNEL_CTXNUM, 0);
+        bs->kernel_dsr = get_gseg_base_address_ds(gru->gs_gru_base_vaddr,
+                                        KERNEL_CTXNUM, 0);
+
+        lock_cch_handle(cch);
+        cch->tfm_fault_bit_enable = 0;
+        cch->tlb_int_enable = 0;
+        cch->tfm_done_bit_enable = 0;
+        cch->unmap_enable = 1;
+        err = cch_allocate(cch, 0, cbr_map, dsr_map);
+        if (err) {
+                gru_dbg(grudev,
+                        "Unable to allocate kernel CCH: gru %d, err %d\n",
+                        gru->gs_gid, err);
+                BUG();
+        }
+        if (cch_start(cch)) {
+                gru_dbg(grudev, "Unable to start kernel CCH: gru %d, err %d\n",
+                        gru->gs_gid, err);
+                BUG();
+        }
+        unlock_cch_handle(cch);
+
+        if (options & GRU_QUICKLOOK)
+                quicktest(gru);
+        return 0;
+}