[PATCH 3/3] drm/i915/guc: Track all sent actions to GuC

[John Harrison]

On 5/26/2023 16:55, John.C.Harrison at Intel.com wrote:
> From: Michal Wajdeczko <michal.wajdeczko at intel.com>
>
> For easier debug of any unexpected error responses from GuC that
> might be related to non-blocking fast requests, track action code (and
> stack if under DEBUG_GUC config) for every H2G request.
>
> Signed-off-by: Michal Wajdeczko <michal.wajdeczko at intel.com>
> Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
Reviewed-by: John Harrison <John.C.Harrison at Intel.com>

> ---
>   drivers/gpu/drm/i915/Kconfig.debug        |  1 +
>   drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 68 ++++++++++++++++++++++-
>   drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h | 11 ++++
>   3 files changed, 77 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/Kconfig.debug b/drivers/gpu/drm/i915/Kconfig.debug
> index 47e845353ffad..2d21930d55015 100644
> --- a/drivers/gpu/drm/i915/Kconfig.debug
> +++ b/drivers/gpu/drm/i915/Kconfig.debug
> @@ -157,6 +157,7 @@ config DRM_I915_SW_FENCE_CHECK_DAG
>   config DRM_I915_DEBUG_GUC
>   	bool "Enable additional driver debugging for GuC"
>   	depends on DRM_I915
> +	select STACKDEPOT
>   	default n
>   	help
>   	  Choose this option to turn on extra driver debugging that may affect
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> index 3a71bb582089e..4aa903be1317b 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> @@ -376,6 +376,24 @@ void intel_guc_ct_disable(struct intel_guc_ct *ct)
>   	}
>   }
>   
> +#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
> +static void ct_track_lost_and_found(struct intel_guc_ct *ct, u32 fence, u32 action)
> +{
> +	unsigned int lost = fence % ARRAY_SIZE(ct->requests.lost_and_found);
> +#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GUC)
> +	unsigned long entries[SZ_32];
> +	unsigned int n;
> +
> +	n = stack_trace_save(entries, ARRAY_SIZE(entries), 1);
> +
> +	/* May be called under spinlock, so avoid sleeping */
> +	ct->requests.lost_and_found[lost].stack = stack_depot_save(entries, n, GFP_NOWAIT);
> +#endif
> +	ct->requests.lost_and_found[lost].fence = fence;
> +	ct->requests.lost_and_found[lost].action = action;
> +}
> +#endif
> +
>   static u32 ct_get_next_fence(struct intel_guc_ct *ct)
>   {
>   	/* For now it's trivial */
> @@ -447,6 +465,11 @@ static int ct_write(struct intel_guc_ct *ct,
>   	}
>   	GEM_BUG_ON(tail > size);
>   
> +#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
> +	ct_track_lost_and_found(ct, fence,
> +				FIELD_GET(GUC_HXG_EVENT_MSG_0_ACTION, action[0]));
> +#endif
> +
>   	/*
>   	 * make sure H2G buffer update and LRC tail update (if this triggering a
>   	 * submission) are visible before updating the descriptor tail
> @@ -953,6 +976,43 @@ static int ct_read(struct intel_guc_ct *ct, struct ct_incoming_msg **msg)
>   	return -EPIPE;
>   }
>   
> +#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
> +static bool ct_check_lost_and_found(struct intel_guc_ct *ct, u32 fence)
> +{
> +	unsigned int n;
> +	char *buf = NULL;
> +	bool found = false;
> +
> +	lockdep_assert_held(&ct->requests.lock);
> +
> +	for (n = 0; n < ARRAY_SIZE(ct->requests.lost_and_found); n++) {
> +		if (ct->requests.lost_and_found[n].fence != fence)
> +			continue;
> +		found = true;
> +
> +#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GUC)
> +		buf = kmalloc(SZ_4K, GFP_NOWAIT);
> +		if (buf && stack_depot_snprint(ct->requests.lost_and_found[n].stack,
> +					       buf, SZ_4K, 0)) {
> +			CT_ERROR(ct, "Fence %u was used by action %#04x sent at\n%s",
> +				 fence, ct->requests.lost_and_found[n].action, buf);
> +			break;
> +		}
> +#endif
> +		CT_ERROR(ct, "Fence %u was used by action %#04x\n",
> +			 fence, ct->requests.lost_and_found[n].action);
> +		break;
> +	}
> +	kfree(buf);
> +	return found;
> +}
> +#else
> +static bool ct_check_lost_and_found(struct intel_guc_ct *ct, u32 fence)
> +{
> +	return false;
> +}
> +#endif
> +
>   static int ct_handle_response(struct intel_guc_ct *ct, struct ct_incoming_msg *response)
>   {
>   	u32 len = FIELD_GET(GUC_CTB_MSG_0_NUM_DWORDS, response->msg[0]);
> @@ -996,9 +1056,11 @@ static int ct_handle_response(struct intel_guc_ct *ct, struct ct_incoming_msg *r
>   	if (!found) {
>   		CT_ERROR(ct, "Unsolicited response message: len %u, data %#x (fence %u, last %u)\n",
>   			 len, hxg[0], fence, ct->requests.last_fence);
> -		list_for_each_entry(req, &ct->requests.pending, link)
> -			CT_ERROR(ct, "request %u awaits response\n",
> -				 req->fence);
> +		if (!ct_check_lost_and_found(ct, fence)) {
> +			list_for_each_entry(req, &ct->requests.pending, link)
> +				CT_ERROR(ct, "request %u awaits response\n",
> +					 req->fence);
> +		}
>   		err = -ENOKEY;
>   	}
>   	spin_unlock_irqrestore(&ct->requests.lock, flags);
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h
> index 818415b64f4d1..58e42901ff498 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h
> @@ -8,6 +8,7 @@
>   
>   #include <linux/interrupt.h>
>   #include <linux/spinlock.h>
> +#include <linux/stackdepot.h>
>   #include <linux/workqueue.h>
>   #include <linux/ktime.h>
>   #include <linux/wait.h>
> @@ -81,6 +82,16 @@ struct intel_guc_ct {
>   
>   		struct list_head incoming; /* incoming requests */
>   		struct work_struct worker; /* handler for incoming requests */
> +
> +#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
> +		struct {
> +			u16 fence;
> +			u16 action;
> +#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GUC)
> +			depot_stack_handle_t stack;
> +#endif
> +		} lost_and_found[SZ_16];
> +#endif
>   	} requests;
>   
>   	/** @stall_time: time of first time a CTB submission is stalled */