Re: [PATCH] drm/i915/selftests: Try to recover from a wedged GPU during reset tests

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> If we see the seqno stop progressing, we abandon the test for fear that
> the GPU died following the reset. However, during test teardown we still
> wait for the GPU to idle before continuing, but we have already
> confirmed that the GPU is dead. Furthermore, since we are inside a reset
> test, we have disabled the hangchecker, and so there is no safety net and
> we wait indefinitely. Detect the stuck GPU and declare it wedged as a
> state of emergency so we can escape.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Jari Tahvanainen <jari.tahvanainen@intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/selftests/intel_hangcheck.c | 25 +++++++++++++++++++-----
>  1 file changed, 20 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/selftests/intel_hangcheck.c b/drivers/gpu/drm/i915/selftests/intel_hangcheck.c
> index 02e52a146ed8..913fe752f6b4 100644
> --- a/drivers/gpu/drm/i915/selftests/intel_hangcheck.c
> +++ b/drivers/gpu/drm/i915/selftests/intel_hangcheck.c
> @@ -165,6 +165,7 @@ static int emit_recurse_batch(struct hang *h,
>  		*batch++ = lower_32_bits(vma->node.start);
>  	}
>  	*batch++ = MI_BATCH_BUFFER_END; /* not reached */
> +	wmb();
>

Why not the big hammer with i915_gem_chipset_flush() here?

>  	flags = 0;
>  	if (INTEL_GEN(vm->i915) <= 5)
> @@ -621,7 +622,12 @@ static int igt_wait_reset(void *arg)
>  	__i915_add_request(rq, true);
>  
>  	if (!wait_for_hang(&h, rq)) {
> -		pr_err("Failed to start request %x\n", rq->fence.seqno);
> +		pr_err("Failed to start request %x, at %x\n",
> +		       rq->fence.seqno, hws_seqno(&h, rq));
> +
> +		i915_reset(i915, 0);
> +		i915_gem_set_wedged(i915);
> +
>  		err = -EIO;
>  		goto out_rq;
>  	}
> @@ -708,10 +714,14 @@ static int igt_reset_queue(void *arg)
>  			__i915_add_request(rq, true);
>  
>  			if (!wait_for_hang(&h, prev)) {
> -				pr_err("Failed to start request %x\n",
> -				       prev->fence.seqno);
> +				pr_err("Failed to start request %x, at %x\n",
> +				       rq->fence.seqno, hws_seqno(&h, rq));

As you pointed out the debug in here is for wrong request.

Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>

>  				i915_gem_request_put(rq);
>  				i915_gem_request_put(prev);
> +
> +				i915_reset(i915, 0);
> +				i915_gem_set_wedged(i915);
> +
>  				err = -EIO;
>  				goto fini;
>  			}
> @@ -806,7 +816,12 @@ static int igt_handle_error(void *arg)
>  	__i915_add_request(rq, true);
>  
>  	if (!wait_for_hang(&h, rq)) {
> -		pr_err("Failed to start request %x\n", rq->fence.seqno);
> +		pr_err("Failed to start request %x, at %x\n",
> +		       rq->fence.seqno, hws_seqno(&h, rq));
> +
> +		i915_reset(i915, 0);
> +		i915_gem_set_wedged(i915);
> +
>  		err = -EIO;
>  		goto err_request;
>  	}
> @@ -843,8 +858,8 @@ static int igt_handle_error(void *arg)
>  int intel_hangcheck_live_selftests(struct drm_i915_private *i915)
>  {
>  	static const struct i915_subtest tests[] = {
> +		SUBTEST(igt_global_reset), /* attempt to recover GPU first */
>  		SUBTEST(igt_hang_sanitycheck),
> -		SUBTEST(igt_global_reset),
>  		SUBTEST(igt_reset_engine),
>  		SUBTEST(igt_reset_active_engines),
>  		SUBTEST(igt_wait_reset),
> -- 
> 2.14.1
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