<div dir="ltr">Wow, this patch made intel-compute-runtime suddenly start working properly instead of causing a "GPU hang" that wasn't really a hang but instead a seqno overflow. </div> <div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, May 7, 2023 at 5:53 PM Matthew Brost <<a href="mailto:matthew.brost@intel.com">matthew.brost@intel.com</a>> wrote: </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On Fri, May 05, 2023 at 03:49:10PM +0100, Matthew Auld wrote: > Checking seqno_recv >= seqno looks like it will incorrectly report true > when the seqno has wrapped (not unlikely given > TLB_INVALIDATION_SEQNO_MAX). Calling xe_gt_tlb_invalidation_wait() might > then return before the flush has been completed by the GuC. > > Fix this by treating a large negative delta as an indication that the > seqno has wrapped around. Similar to how we treat a large positive delta > as an indication that the seqno_recv must have wrapped around, but in > that case the seqno has likely also signalled. > > It looks like we could also potentially make the seqno use the full > 32bits as supported by the GuC. Yea we def could use more of the space but in the end we have the seqno wrap issue. I think I set this to a low value to prove the wrapping protection worked (it didn't) by triigering wraps more often than the wrapping 32 bits. With, this patch LGTM. Reviewed-by: Matthew Brost <<a href="mailto:matthew.brost@intel.com" target="_blank">matthew.brost@intel.com</a>> > > Signed-off-by: Matthew Auld <<a href="mailto:matthew.auld@intel.com" target="_blank">matthew.auld@intel.com</a>> > Cc: Thomas Hellström <<a href="mailto:thomas.hellstrom@linux.intel.com" target="_blank">thomas.hellstrom@linux.intel.com</a>> > Cc: Matthew Brost <<a href="mailto:matthew.brost@intel.com" target="_blank">matthew.brost@intel.com</a>> > --- > drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c b/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c > index 604f189dbd70..67822b3dd353 100644 > --- a/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c > +++ b/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c > @@ -251,14 +251,15 @@ int xe_gt_tlb_invalidation_vma(struct xe_gt *gt, > > static bool tlb_invalidation_seqno_past(struct xe_gt *gt, int seqno) > { > - if (gt->tlb_invalidation.seqno_recv >= seqno) > - return true; > + if (seqno - gt->tlb_invalidation.seqno_recv < > + -(TLB_INVALIDATION_SEQNO_MAX / 2)) > + return false; > > if (seqno - gt->tlb_invalidation.seqno_recv > > (TLB_INVALIDATION_SEQNO_MAX / 2)) > return true; > > - return false; > + return gt->tlb_invalidation.seqno_recv >= seqno; > } > > /** > -- > 2.40.0 > </blockquote></div>