[Intel-gfx] [PATCH i-g-t v3] tests/drv_hangman: test for acthd increasing through invalid VM space

[Mika Kuoppala]

daniele.ceraolospurio at intel.com writes:

> From: Daniele Ceraolo Spurio <daniele.ceraolospurio at 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
>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Cc: Arun Siluvery <arun.siluvery at linux.intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> ---
>  tests/drv_hangman.c | 39 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
>
> diff --git a/tests/drv_hangman.c b/tests/drv_hangman.c
> index 8a465cf..2360f26 100644
> --- a/tests/drv_hangman.c
> +++ b/tests/drv_hangman.c
> @@ -288,6 +288,42 @@ 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);
> +	igt_assert_eq(gem_wait(fd, handle, &timeout_ns), 0);

Chris pointed out in irc that if end up timeouting, that
means runaway head is there still progressing.

In order to make the gpu usable again, we need to forcereset
the gpu. Stop rings doesn't help at here anymore so
forcing 'echo 1 >i915_wedged_set should do the trick.

-Mika



> +
> +	close(fd);
> +}
> +
>  igt_main
>  {
>  	const struct intel_execution_engine *e;
> @@ -314,4 +350,7 @@ igt_main
>  			test_error_state_capture(e->exec_id | e->flags,
>  						 e->full_name);
>  	}
> +
> +	igt_subtest("hangcheck-unterminated")
> +		hangcheck_unterminated();
>  }
> -- 
> 1.9.1