Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> The idea behind using an illegal instruction was to hang the GPU must
> faster than simply using the recursive batch. However, we stopped doing
> so on gen8+ as the CS parser was much laxer and allowed the illegal
> command through but still interpreted the packet length (jumping over
> the recursive batch buffer start that followed). Sandybridge doesn't
> just hang the GPU when it encounters an illegal command on the BLT
> engine, it hangs the machine. That goes above and beyond testing our
> hangcheck + reset, so remove the deadly instructions.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> lib/igt_gt.c | 25 +++++--------------------
> 1 file changed, 5 insertions(+), 20 deletions(-)
>
> diff --git a/lib/igt_gt.c b/lib/igt_gt.c
> index 6f7daa5e..d5e8b557 100644
> --- a/lib/igt_gt.c
> +++ b/lib/igt_gt.c
> @@ -270,30 +270,15 @@ igt_hang_t igt_hang_ctx(int fd,
>
> memset(b, 0xc5, sizeof(b));
>
> - /*
> - * We emit invalid command to provoke a gpu hang.
> - * If that doesn't work, we do bb start loop.
> - * Note that the bb start aligment is illegal due this.
> - * But hey, we are here to hang the gpu so whatever works.
> - * We skip 0xfffffff on gen9 as it confuses hw in an such a way that
> - * it will skip over the bb start, causing runaway head and
> - * thus much slower hang detection.
> - */
Daydreaming about MI_HALT,
Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
> len = 2;
> - if (intel_gen(intel_get_drm_devid(fd)) >= 8) {
> - b[0] = MI_NOOP;
> + if (intel_gen(intel_get_drm_devid(fd)) >= 8)
> len++;
> - } else {
> - b[0] = 0xffffffff;
> - }
> -
> - b[1] = MI_BATCH_BUFFER_START | (len - 2);
> - b[1+len] = MI_BATCH_BUFFER_END;
> - b[2+len] = MI_NOOP;
> + b[0] = MI_BATCH_BUFFER_START | (len - 2);
> + b[len] = MI_BATCH_BUFFER_END;
> + b[len+1] = MI_NOOP;
> gem_write(fd, exec.handle, 0, b, sizeof(b));
>
> - reloc.offset = 8;
> - reloc.delta = 4;
> + reloc.offset = sizeof(uint32_t);
> reloc.target_handle = exec.handle;
> reloc.read_domains = I915_GEM_DOMAIN_COMMAND;
>
> --
> 2.13.3
>
> _______________________________________________
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> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
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