Re: [PATCH i-g-t v4 2/2] tests/drv_hangman: test for acthd increasing through invalid VM space

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

daniele.ceraolospurio@intel.com writes:

> From: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
>
> The hangcheck logic will not flag an hang if acthd keeps increasing.
> However, if a malformed batch jumps to an invalid offset in the ppgtt it
> can potentially continue executing through the whole address space
> without triggering the hangcheck mechanism.
>
> This patch adds a test to simulate the issue. I've kept the test running
> for more than 10 minutes before killing it on a BDW and no hang occurred.
> I've sampled i915_hangcheck_info a few times during the run and got the
> following:
>
> Hangcheck active, fires in 468ms
> render ring:
> 	seqno = fffff55e [current fffff55e]
> 	ACTHD = 0x47df685ecc [current 0x4926b81d90]
> 	max ACTHD = 0x47df685ecc
> 	score = 0
> 	action = 2
> 	instdone read = 0xffd7ffff 0xffffffff 0xffffffff 0xffffffff
> 	instdone accu = 0x00000000 0x00000000 0x00000000 0x00000000
>
> Hangcheck active, fires in 424ms
> render ring:
> 	seqno = fffff55e [current fffff55e]
> 	ACTHD = 0x6c953d3a34 [current 0x6de5e76fa4]
> 	max ACTHD = 0x6c953d3a34
> 	score = 0
> 	action = 2
> 	instdone read = 0xffd7ffff 0xffffffff 0xffffffff 0xffffffff
> 	instdone accu = 0x00000000 0x00000000 0x00000000 0x00000000
>
> Hangcheck active, fires in 1692ms
> render ring:
> 	seqno = fffff55e [current fffff55e]
> 	ACTHD = 0x1f49b0366dc [current 0x1f4dcbd88ec]
> 	max ACTHD = 0x1f49b0366dc
> 	score = 0
> 	action = 2
> 	instdone read = 0xffd7ffff 0xffffffff 0xffffffff 0xffffffff
> 	instdone accu = 0x00000000 0x00000000 0x00000000 0x00000000
>
> v2: use the new gem_wait() function (Chris)
>
> v3: switch to unterminated batch and rename test, remove redundant
>     check, update test requirements (Chris), update top comment
>
> v4: force gpu reset if the hang detection fails (Mika)
>
> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> Cc: Arun Siluvery <arun.siluvery@linux.intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Daniele Ceraolo Spurio
> <daniele.ceraolospurio@intel.com>

Both patches pushed. Thank you all.
-Mika

> ---
>  tests/drv_hangman.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
>
> diff --git a/tests/drv_hangman.c b/tests/drv_hangman.c
> index a4f187a..a1a3faa 100644
> --- a/tests/drv_hangman.c
> +++ b/tests/drv_hangman.c
> @@ -284,6 +284,47 @@ static void test_error_state_capture(unsigned ring_id,
>  	check_error_state(gen, cmd_parser, ring_name, offset);
>  }
>  
> +
> +/* This test covers the case where we end up in an uninitialised area of the
> + * ppgtt and keep executing through it. This is particularly relevant if 48b
> + * ppgtt is enabled because the ppgtt is massively bigger compared to the 32b
> + * case and it takes a lot more time to wrap, so the acthd can potentially keep
> + * increasing for a long time
> + */
> +#define NSEC_PER_SEC	1000000000L
> +static void hangcheck_unterminated(void)
> +{
> +	int fd;
> +	/* timeout needs to be greater than ~5*hangcheck */
> +	int64_t timeout_ns = 100 * NSEC_PER_SEC; /* 100 seconds */
> +	struct drm_i915_gem_execbuffer2 execbuf;
> +	struct drm_i915_gem_exec_object2 gem_exec;
> +	uint32_t handle;
> +
> +	fd = drm_open_driver(DRIVER_INTEL);
> +	igt_require(gem_uses_full_ppgtt(fd));
> +	igt_require_hang_ring(fd, 0);
> +
> +	handle = gem_create(fd, 4096);
> +
> +	memset(&gem_exec, 0, sizeof(gem_exec));
> +	gem_exec.handle = handle;
> +
> +	memset(&execbuf, 0, sizeof(execbuf));
> +	execbuf.buffers_ptr = (uintptr_t)&gem_exec;
> +	execbuf.buffer_count = 1;
> +	execbuf.batch_len = 8;
> +
> +	gem_execbuf(fd, &execbuf);
> +	if (gem_wait(fd, handle, &timeout_ns) != 0) {
> +		/* need to manually trigger an hang to clean before failing */
> +		igt_force_gpu_reset();
> +		igt_assert_f(0, "unterminated batch did not trigger an hang!");
> +	}
> +
> +	close(fd);
> +}
> +
>  igt_main
>  {
>  	const struct intel_execution_engine *e;
> @@ -310,4 +351,7 @@ igt_main
>  			test_error_state_capture(e->exec_id | e->flags,
>  						 e->full_name);
>  	}
> +
> +	igt_subtest("hangcheck-unterminated")
> +		hangcheck_unterminated();
>  }
> -- 
> 1.9.1
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