Re: [PATCH 1/3] drm/i915/guc: keep GuC doorbell & process descriptor mapped in kernel

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 19/04/16 16:08, Dave Gordon wrote:
> 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>
> ---
>   drivers/gpu/drm/i915/i915_guc_submission.c | 66 +++++++++++++-----------------
>   drivers/gpu/drm/i915/intel_guc.h           |  2 +
>   2 files changed, 30 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
> index da86bdb..d251699 100644
> --- 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 3bb85b1..06050c241a 100644
> --- 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 {
>

Looks correct,

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx