In bugzilla, there are some very weird bugs on SNB GT1 whereby the seqno stop being written, but the GPU is otherwise functional, well the command streamer at least! However, since the seqno were not being updated any waits upon rendering results hung, triggering the GPU hang detector. I found a very similar hang when running igt/gem_exec_whisper on a SNB GT1 and after playing around came to the conclusion that: (a) it depends on timing, enabling debug and other slowdowns masks the bug; (b) it was not context size, as increasing the allocation to 128KiB made no difference; (c) it depended upon placement as restricting the binding to the mappable region works; (d) it depended upon alignment of the context binding, though the bspec still only lists the restriction as 4k Changing the alignment constrainst seems to be least intrusive, and though I have not been able to reproduce this on snb-gt2 and all the recent bugs to the best of my knowledge have been snb-gt1, it is safer to apply the constraint to all snb. Though I am still a little wary that is merely a side-effect that is papering over the issue (for example, it may be placement of the context next to another object that is causng the issue, or it may be finding the new alignment slows down context switches enough etc). Testcase: igt/gem_exec_whisper/render-contexts-interruptible #snb-gt1 References: (e.g.) https://bugs.freedesktop.org/show_bug.cgi?id=93262 Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx --- drivers/gpu/drm/i915/i915_gem_context.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c index 394e525e55f1..f0883a968e11 100644 --- a/drivers/gpu/drm/i915/i915_gem_context.c +++ b/drivers/gpu/drm/i915/i915_gem_context.c @@ -94,7 +94,7 @@ * I've seen in a spec to date, and that was a workaround for a non-shipping * part. It should be safe to decrease this, but it's more future proof as is. */ -#define GEN6_CONTEXT_ALIGN (64<<10) +#define GEN6_CONTEXT_ALIGN (256<<10) #define GEN7_CONTEXT_ALIGN 4096 static size_t get_context_alignment(struct drm_device *dev) -- 2.8.0.rc3 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
