On Fri, 23 Dec 2022, Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> wrote: > On 23/12/2022 12:18, Andi Shyti wrote: >> From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> >> >> On Haswell, in particular, we see an issue where resets fails because >> the engine resumes from an incorrect RING_HEAD. Since the RING_HEAD >> doesn't point to the remaining requests to re-run, but may instead point >> into the uninitialised portion of the ring, the GPU may be then fed >> invalid instructions from a privileged context, often pushing the GPU >> into an unrecoverable hang. >> >> If at first the write doesn't succeed, try, try again. >> >> References: https://gitlab.freedesktop.org/drm/intel/-/issues/5432 >> References: https://gitlab.freedesktop.org/drm/intel/-/issues/3303 >> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> >> Cc: Andrzej Hajda <andrzej.hajda@xxxxxxxxx> >> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx> >> Signed-off-by: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx> >> --- >> .../gpu/drm/i915/gt/intel_ring_submission.c | 44 +++++++++++++------ >> drivers/gpu/drm/i915/i915_utils.h | 8 ++++ >> 2 files changed, 38 insertions(+), 14 deletions(-) >> >> diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c b/drivers/gpu/drm/i915/gt/intel_ring_submission.c >> index 827adb0cfaea6..cdf283f5b1427 100644 >> --- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c >> +++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c >> @@ -192,6 +192,7 @@ static bool stop_ring(struct intel_engine_cs *engine) >> static int xcs_resume(struct intel_engine_cs *engine) >> { >> struct intel_ring *ring = engine->legacy.ring; >> + ktime_t kt; >> >> ENGINE_TRACE(engine, "ring:{HEAD:%04x, TAIL:%04x}\n", >> ring->head, ring->tail); >> @@ -230,9 +231,20 @@ static int xcs_resume(struct intel_engine_cs *engine) >> set_pp_dir(engine); >> >> /* First wake the ring up to an empty/idle ring */ >> - ENGINE_WRITE_FW(engine, RING_HEAD, ring->head); >> + until_timeout_ns(kt, 2 * NSEC_PER_MSEC) { >> + ENGINE_WRITE_FW(engine, RING_HEAD, ring->head); >> + if (ENGINE_READ_FW(engine, RING_HEAD) == ring->head) >> + break; >> + } > > 2ms?! Shudder.. > > #define done \ > ({ \ > ENGINE_WRITE_FW(engine, RING_HEAD, ring->head); \ > ENGINE_READ_FW(engine, RING_HEAD) == ring->head; \ > }) > _wait_for_atomic(done, 2 * USEC_PER_MSEC, needs_to_be_atomic_or_not?); > #undef done > > Should work and avoid the need to add yet another helper, please > double-check. Not as pretty, but accumulating generic sounding helpers > in i915_utils.h is a bit frowned upon. Yeah, please no more helpers like this. They're not helping. BR, Jani. > > Regards, > > Tvrtko > >> + >> ENGINE_WRITE_FW(engine, RING_TAIL, ring->head); >> - ENGINE_POSTING_READ(engine, RING_TAIL); >> + if (ENGINE_READ_FW(engine, RING_HEAD) != ENGINE_READ_FW(engine, RING_TAIL)) { >> + ENGINE_TRACE(engine, "failed to reset empty ring: [%x, %x]: %x\n", >> + ENGINE_READ_FW(engine, RING_HEAD), >> + ENGINE_READ_FW(engine, RING_TAIL), >> + ring->head); >> + goto err; >> + } >> >> ENGINE_WRITE_FW(engine, RING_CTL, >> RING_CTL_SIZE(ring->size) | RING_VALID); >> @@ -241,12 +253,16 @@ static int xcs_resume(struct intel_engine_cs *engine) >> if (__intel_wait_for_register_fw(engine->uncore, >> RING_CTL(engine->mmio_base), >> RING_VALID, RING_VALID, >> - 5000, 0, NULL)) >> + 5000, 0, NULL)) { >> + ENGINE_TRACE(engine, "failed to restart\n"); >> goto err; >> + } >> >> - if (GRAPHICS_VER(engine->i915) > 2) >> + if (GRAPHICS_VER(engine->i915) > 2) { >> ENGINE_WRITE_FW(engine, >> RING_MI_MODE, _MASKED_BIT_DISABLE(STOP_RING)); >> + ENGINE_POSTING_READ(engine, RING_MI_MODE); >> + } >> >> /* Now awake, let it get started */ >> if (ring->tail != ring->head) { >> @@ -259,16 +275,16 @@ static int xcs_resume(struct intel_engine_cs *engine) >> return 0; >> >> err: >> - drm_err(&engine->i915->drm, >> - "%s initialization failed; " >> - "ctl %08x (valid? %d) head %08x [%08x] tail %08x [%08x] start %08x [expected %08x]\n", >> - engine->name, >> - ENGINE_READ(engine, RING_CTL), >> - ENGINE_READ(engine, RING_CTL) & RING_VALID, >> - ENGINE_READ(engine, RING_HEAD), ring->head, >> - ENGINE_READ(engine, RING_TAIL), ring->tail, >> - ENGINE_READ(engine, RING_START), >> - i915_ggtt_offset(ring->vma)); >> + ENGINE_TRACE(engine, >> + "initialization failed; " >> + "ctl %08x (valid? %d) head %08x [%08x] tail %08x [%08x] start %08x [expected %08x]\n", >> + ENGINE_READ(engine, RING_CTL), >> + ENGINE_READ(engine, RING_CTL) & RING_VALID, >> + ENGINE_READ(engine, RING_HEAD), ring->head, >> + ENGINE_READ(engine, RING_TAIL), ring->tail, >> + ENGINE_READ(engine, RING_START), >> + i915_ggtt_offset(ring->vma)); >> + GEM_TRACE_DUMP(); >> return -EIO; >> } >> >> diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h >> index b64192d9c7daa..f24a25c0685e1 100644 >> --- a/drivers/gpu/drm/i915/i915_utils.h >> +++ b/drivers/gpu/drm/i915/i915_utils.h >> @@ -254,6 +254,14 @@ wait_remaining_ms_from_jiffies(unsigned long timestamp_jiffies, int to_wait_ms) >> } >> } >> >> +/** >> + * until_timeout_ns - Keep retrying (busy spin) until the duration has passed >> + */ >> +#define until_timeout_ns(end, timeout_ns) \ >> + for ((end) = ktime_get() + (timeout_ns); \ >> + ktime_before(ktime_get(), (end)); \ >> + cpu_relax()) >> + > /** >> * __wait_for - magic wait macro >> * -- Jani Nikula, Intel Open Source Graphics Center
