drm/i915/guc: keep GuC doorbell & process descriptor mapped in kernel

Don't use kmap_atomic() for doorbell & process descriptor access.
This patch fixes the BUG shown below, where the thread could sleep
while holding a kmap_atomic mapping. In order not to need to call
kmap_atomic() in this code path, we now set up a permanent kernel
mapping of the shared doorbell and process-descriptor page, and
use that in all doorbell and process-descriptor related code.

  BUG: scheduling while atomic: gem_close_race/1941/0x00000002
  Modules linked in: hid_generic usbhid i915 asix usbnet libphy mii
    i2c_algo_bit drm_kms_helper cfbfillrect syscopyarea cfbimgblt
    sysfillrect sysimgblt fb_sys_fops cfbcopyarea drm coretemp i2c_hid
    hid video pinctrl_sunrisepoint pinctrl_intel acpi_pad nls_iso8859_1
    e1000e ptp psmouse pps_core ahci libahci
  CPU: 0 PID: 1941 Comm: gem_close_race Tainted: G     U 4.4.0-160121+ #123
  Hardware name: Intel Corporation Skylake Client platform/Skylake AIO
    DDR3L RVP10, BIOS SKLSE2R1.R00.X100.B01.1509220551 09/22/2015
    0000000000013e40 ffff880166c27a78 ffffffff81280d02 ffff880172c13e40
    ffff880166c27a88 ffffffff810c203a ffff880166c27ac8 ffffffff814ec808
    ffff88016b7c6000 ffff880166c28000 00000000000f4240 0000000000000001
  Call Trace:
    [<ffffffff81280d02>] dump_stack+0x4b/0x79
    [<ffffffff810c203a>] __schedule_bug+0x41/0x4f
    [<ffffffff814ec808>] __schedule+0x5a8/0x690
    [<ffffffff814ec927>] schedule+0x37/0x80
    [<ffffffff814ef3fd>] schedule_hrtimeout_range_clock+0xad/0x130
    [<ffffffff81090be0>] ? hrtimer_init+0x10/0x10
    [<ffffffff814ef3f1>] ?  schedule_hrtimeout_range_clock+0xa1/0x130
    [<ffffffff814ef48e>] schedule_hrtimeout_range+0xe/0x10
    [<ffffffff814eef9b>] usleep_range+0x3b/0x40
    [<ffffffffa01ec109>] i915_guc_wq_check_space+0x119/0x210 [i915]
    [<ffffffffa01da47c>] intel_logical_ring_alloc_request_extras+0x5c/0x70 [i915]
    [<ffffffffa01cdbf1>] i915_gem_request_alloc+0x91/0x170 [i915]
    [<ffffffffa01c1c07>] i915_gem_do_execbuffer.isra.25+0xbc7/0x12a0 [i915]
    [<ffffffffa01cb785>] ?  i915_gem_object_get_pages_gtt+0x225/0x3c0 [i915]
    [<ffffffffa01d1fb6>] ? i915_gem_pwrite_ioctl+0xd6/0x9f0 [i915]
    [<ffffffffa01c2e68>] i915_gem_execbuffer2+0xa8/0x250 [i915]
    [<ffffffffa00f65d8>] drm_ioctl+0x258/0x4f0 [drm]
    [<ffffffffa01c2dc0>] ? i915_gem_execbuffer+0x340/0x340 [i915]
    [<ffffffff8111590d>] do_vfs_ioctl+0x2cd/0x4a0
    [<ffffffff8111eac2>] ? __fget+0x72/0xb0
    [<ffffffff81115b1c>] SyS_ioctl+0x3c/0x70
    [<ffffffff814effd7>] entry_SYSCALL_64_fastpath+0x12/0x6a
  ------------[ cut here ]------------

v4:
  Only tear down doorbell & kunmap() client object if we actually
  succeeded in allocating a client object (Tvrtko Ursulin)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93847
Original-version-by: Alex Dai <yu.dai@intel.com>
Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
Cc: Tvtrko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
index da86bdbba275cebd62d5e88a4d80c3b6056c634e..d251699c53ae3840da72910adf753f0d4b5129d2 100644 (file)
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -179,15 +179,11 @@ static void guc_init_doorbell(struct intel_guc *guc,
                              struct i915_guc_client *client)
 {
        struct guc_doorbell_info *doorbell;
-       void *base;
 
-       base = kmap_atomic(i915_gem_object_get_page(client->client_obj, 0));
-       doorbell = base + client->doorbell_offset;
+       doorbell = client->client_base + client->doorbell_offset;
 
-       doorbell->db_status = 1;
+       doorbell->db_status = GUC_DOORBELL_ENABLED;
        doorbell->cookie = 0;
-
-       kunmap_atomic(base);
 }
 
 static int guc_ring_doorbell(struct i915_guc_client *gc)
@@ -195,11 +191,9 @@ static int guc_ring_doorbell(struct i915_guc_client *gc)
        struct guc_process_desc *desc;
        union guc_doorbell_qw db_cmp, db_exc, db_ret;
        union guc_doorbell_qw *db;
-       void *base;
        int attempt = 2, ret = -EAGAIN;
 
-       base = kmap_atomic(i915_gem_object_get_page(gc->client_obj, 0));
-       desc = base + gc->proc_desc_offset;
+       desc = gc->client_base + gc->proc_desc_offset;
 
        /* Update the tail so it is visible to GuC */
        desc->tail = gc->wq_tail;
@@ -215,7 +209,7 @@ static int guc_ring_doorbell(struct i915_guc_client *gc)
                db_exc.cookie = 1;
 
        /* pointer of current doorbell cacheline */
-       db = base + gc->doorbell_offset;
+       db = gc->client_base + gc->doorbell_offset;
 
        while (attempt--) {
                /* lets ring the doorbell */
@@ -247,7 +241,6 @@ static int guc_ring_doorbell(struct i915_guc_client *gc)
        /* Finally, update the cached copy of the GuC's WQ head */
        gc->wq_head = desc->head;
 
-       kunmap_atomic(base);
        return ret;
 }
 
@@ -256,16 +249,12 @@ static void guc_disable_doorbell(struct intel_guc *guc,
 {
        struct drm_i915_private *dev_priv = guc_to_i915(guc);
        struct guc_doorbell_info *doorbell;
-       void *base;
        i915_reg_t drbreg = GEN8_DRBREGL(client->doorbell_id);
        int value;
 
-       base = kmap_atomic(i915_gem_object_get_page(client->client_obj, 0));
-       doorbell = base + client->doorbell_offset;
+       doorbell = client->client_base + client->doorbell_offset;
 
-       doorbell->db_status = 0;
-
-       kunmap_atomic(base);
+       doorbell->db_status = GUC_DOORBELL_DISABLED;
 
        I915_WRITE(drbreg, I915_READ(drbreg) & ~GEN8_DRB_VALID);
 
@@ -341,10 +330,8 @@ static void guc_init_proc_desc(struct intel_guc *guc,
                               struct i915_guc_client *client)
 {
        struct guc_process_desc *desc;
-       void *base;
 
-       base = kmap_atomic(i915_gem_object_get_page(client->client_obj, 0));
-       desc = base + client->proc_desc_offset;
+       desc = client->client_base + client->proc_desc_offset;
 
        memset(desc, 0, sizeof(*desc));
 
@@ -361,8 +348,6 @@ static void guc_init_proc_desc(struct intel_guc *guc,
        desc->wq_size_bytes = client->wq_size;
        desc->wq_status = WQ_STATUS_ACTIVE;
        desc->priority = client->priority;
-
-       kunmap_atomic(base);
 }
 
 /*
@@ -474,7 +459,6 @@ static void guc_fini_ctx_desc(struct intel_guc *guc,
 int i915_guc_wq_check_space(struct i915_guc_client *gc)
 {
        struct guc_process_desc *desc;
-       void *base;
        u32 size = sizeof(struct guc_wq_item);
        int ret = -ETIMEDOUT, timeout_counter = 200;
 
@@ -486,8 +470,7 @@ int i915_guc_wq_check_space(struct i915_guc_client *gc)
        if (CIRC_SPACE(gc->wq_tail, gc->wq_head, gc->wq_size) >= size)
                return 0;
 
-       base = kmap_atomic(i915_gem_object_get_page(gc->client_obj, 0));
-       desc = base + gc->proc_desc_offset;
+       desc = gc->client_base + gc->proc_desc_offset;
 
        while (timeout_counter-- > 0) {
                gc->wq_head = desc->head;
@@ -501,8 +484,6 @@ int i915_guc_wq_check_space(struct i915_guc_client *gc)
                        usleep_range(1000, 2000);
        };
 
-       kunmap_atomic(base);
-
        return ret;
 }
 
@@ -661,21 +642,28 @@ static void guc_client_free(struct drm_device *dev,
        if (!client)
                return;
 
-       if (client->doorbell_id != GUC_INVALID_DOORBELL_ID) {
-               /*
-                * First disable the doorbell, then tell the GuC we've
-                * finished with it, finally deallocate it in our bitmap
-                */
-               guc_disable_doorbell(guc, client);
-               host2guc_release_doorbell(guc, client);
-               release_doorbell(guc, client->doorbell_id);
-       }
-
        /*
         * XXX: wait for any outstanding submissions before freeing memory.
         * Be sure to drop any locks
         */
 
+       if (client->client_base) {
+               /*
+                * If we got as far as setting up a doorbell, make sure
+                * we shut it down before unmapping & deallocating the
+                * memory. So first disable the doorbell, then tell the
+                * GuC that we've finished with it, finally deallocate
+                * it in our bitmap
+                */
+               if (client->doorbell_id != GUC_INVALID_DOORBELL_ID) {
+                       guc_disable_doorbell(guc, client);
+                       host2guc_release_doorbell(guc, client);
+                       release_doorbell(guc, client->doorbell_id);
+               }
+
+               kunmap(kmap_to_page(client->client_base));
+       }
+
        gem_release_guc_obj(client->client_obj);
 
        if (client->ctx_index != GUC_INVALID_CTX_ID) {
@@ -696,7 +684,7 @@ static void guc_client_free(struct drm_device *dev,
  * @ctx:       the context that owns the client (we use the default render
  *             context)
  *
- * Return:     An i915_guc_client object if success.
+ * Return:     An i915_guc_client object if success, else NULL.
  */
 static struct i915_guc_client *guc_client_alloc(struct drm_device *dev,
                                                uint32_t priority,
@@ -728,7 +716,9 @@ static struct i915_guc_client *guc_client_alloc(struct drm_device *dev,
        if (!obj)
                goto err;
 
+       /* We'll keep just the first (doorbell/proc) page permanently kmap'd. */
        client->client_obj = obj;
+       client->client_base = kmap(i915_gem_object_get_page(obj, 0));
        client->wq_offset = GUC_DB_SIZE;
        client->wq_size = GUC_WQ_SIZE;
 

diff --git a/drivers/gpu/drm/i915/intel_guc.h b/drivers/gpu/drm/i915/intel_guc.h
index 3bb85b127cb0d6fcd336d10168604f03fba11342..06050c241ad4bf276a875387b81028be995fb5cf 100644 (file)
--- a/drivers/gpu/drm/i915/intel_guc.h
+++ b/drivers/gpu/drm/i915/intel_guc.h
@@ -31,6 +31,7 @@ struct drm_i915_gem_request;
 
 struct i915_guc_client {
        struct drm_i915_gem_object *client_obj;
+       void *client_base;              /* first page (only) of above   */
        struct intel_context *owner;
        struct intel_guc *guc;
        uint32_t priority;
@@ -52,6 +53,7 @@ struct i915_guc_client {
        uint32_t q_fail;
        uint32_t b_fail;
        int retcode;
+       int spare;                      /* pad to 32 DWords             */
 };
 
 enum intel_guc_fw_status {