Re: [PATCH v2 09/12] drm/xe: Add xe_tlb_inval_idle helper

["Summers, Stuart" <stuart.summers@intel.com>]

On Mon, 2025-11-10 at 18:48 +0000, Summers, Stuart wrote:
> On Tue, 2025-11-04 at 11:56 -0800, Matthew Brost wrote:
> > Introduce the xe_tlb_inval_idle helper to detect whether any TLB
> > invalidations are currently in flight. This is used in context-
> > based
> > TLB
> > invalidations to determine whether dummy TLB invalidations need to
> > be
> > sent to maintain proper TLB invalidation fence ordering..
> > 
> > v2:
> >  - Implement xe_tlb_inval_idle based on pending list
> > 
> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> 
> I don't have any issue with this patch or the next one, but I want to
> hold on full review until we have a working solution for the
> registration/deregistration placement of this.

Reviewed-by: Stuart Summers <stuart.summers@intel.com>

> 
> Thanks,
> Stuart
> 
> > ---
> >  drivers/gpu/drm/xe/xe_tlb_inval.c | 21 +++++++++++++++++++++
> >  drivers/gpu/drm/xe/xe_tlb_inval.h |  2 ++
> >  2 files changed, 23 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_tlb_inval.c
> > b/drivers/gpu/drm/xe/xe_tlb_inval.c
> > index 7ee081b94f90..7ae6b9f884e9 100644
> > --- a/drivers/gpu/drm/xe/xe_tlb_inval.c
> > +++ b/drivers/gpu/drm/xe/xe_tlb_inval.c
> > @@ -44,11 +44,14 @@ static void xe_tlb_inval_fence_fini(struct
> > xe_tlb_inval_fence *fence)
> >  static void
> >  xe_tlb_inval_fence_signal(struct xe_tlb_inval_fence *fence)
> >  {
> > +       struct xe_tlb_inval *tlb_inval = fence->tlb_inval;
> >         bool stack = test_bit(FENCE_STACK_BIT, &fence->base.flags);
> >  
> >         lockdep_assert_held(&fence->tlb_inval->pending_lock);
> >  
> >         list_del(&fence->link);
> > +       if (list_empty(&tlb_inval->pending_fences))
> > +               cancel_delayed_work(&tlb_inval->fence_tdr);
> >         trace_xe_tlb_inval_fence_signal(fence->tlb_inval->xe,
> > fence);
> >         xe_tlb_inval_fence_fini(fence);
> >         dma_fence_signal(&fence->base);
> > @@ -443,3 +446,21 @@ void xe_tlb_inval_fence_init(struct
> > xe_tlb_inval
> > *tlb_inval,
> >                 dma_fence_get(&fence->base);
> >         fence->tlb_inval = tlb_inval;
> >  }
> > +
> > +/**
> > + * xe_tlb_inval_idle() - Initialize TLB invalidation is idle
> > + * @tlb_inval: TLB invalidation client
> > + *
> > + * Check the TLB invalidation seqno to determine if it is idle
> > (i.e., no TLB
> > + * invalidations are in flight). Expected to be called in the
> > backend after the
> > + * fence has been added to the pending list, and takes this into
> > account.
> > + *
> > + * Return: True if TLB invalidation client is idle, False
> > otherwise
> > + */
> > +bool xe_tlb_inval_idle(struct xe_tlb_inval *tlb_inval)
> > +{
> > +       lockdep_assert_held(&tlb_inval->seqno_lock);
> > +
> > +       guard(spinlock_irq)(&tlb_inval->pending_lock);
> > +       return list_is_singular(&tlb_inval->pending_fences);
> > +}
> > diff --git a/drivers/gpu/drm/xe/xe_tlb_inval.h
> > b/drivers/gpu/drm/xe/xe_tlb_inval.h
> > index 05614915463a..44a6d9177489 100644
> > --- a/drivers/gpu/drm/xe/xe_tlb_inval.h
> > +++ b/drivers/gpu/drm/xe/xe_tlb_inval.h
> > @@ -43,4 +43,6 @@ xe_tlb_inval_fence_wait(struct xe_tlb_inval_fence
> > *fence)
> >  
> >  void xe_tlb_inval_done_handler(struct xe_tlb_inval *tlb_inval, int
> > seqno);
> >  
> > +bool xe_tlb_inval_idle(struct xe_tlb_inval *tlb_inval);
> > +
> >  #endif /* _XE_TLB_INVAL_ */
>