daniele.ceraolospurio@xxxxxxxxx writes:
> From: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxx>
> Cc: Arun Siluvery <arun.siluvery@xxxxxxxxxxxxxxx>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Daniele Ceraolo Spurio
> <daniele.ceraolospurio@xxxxxxxxx>
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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