Re: [PATCH v4 2/3] drm/xe: Log when a timed out TLB invalidation ack finally arrives

[Matthew Brost <matthew.brost@intel.com>]

On Fri, Sep 18, 2026 at 03:06:25PM -0700, Matthew Brost wrote:
> On Thu, Sep 17, 2026 at 01:35:52PM -0300, Tales A. Mendonça wrote:
> > When a TLB invalidation fence times out we log the timeout, but if the
> > ack for that seqno later shows up there is no record of it, making it
> > impossible to tell from logs whether the ack was lost forever or merely
> > (very) late.
> > 
> > Track the most recent timed out seqno and log how late its ack arrives,
> > relative to both the original request and the moment the fence was
> > signaled with -ETIME.
> > 
> > On ARL with GuC 70.53.0 this shows the acks are never lost: they
> > consistently arrive ~2.3s after the request, tens of milliseconds after
> > the TDR has already signaled the fence:
> > 
> >   TLB invalidation fence timeout, seqno=10992 recv=10991
> >   TLB invalidation late ack: seqno=10992 recv=10992,
> >     request-to-ack=2314ms, timeout-to-ack=45ms
> > 
> > Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/work_items/8678
> > Signed-off-by: Tales A. Mendonça <talesam@gmail.com>
> 
> I would give this an RB but my colleagues have done a bunch of work on
> SIGID and I haven't been involved at all, so I need some help here.
> 

I discussed with my colleagues - the we agree the TLB component should
hook into SIGID for logging but we will do this as a follow up on top of
this change.

So this is:
Reviewed-by: Matthew Brost <matthew.brost@intel.com> 

> > ---
> >  drivers/gpu/drm/xe/xe_tlb_inval.c       | 19 +++++++++++++++++++
> >  drivers/gpu/drm/xe/xe_tlb_inval_types.h | 17 +++++++++++++++++
> >  2 files changed, 36 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_tlb_inval.c b/drivers/gpu/drm/xe/xe_tlb_inval.c
> > index 7a0c04fac60..7047a347551 100644
> > --- a/drivers/gpu/drm/xe/xe_tlb_inval.c
> > +++ b/drivers/gpu/drm/xe/xe_tlb_inval.c
> > @@ -14,6 +14,7 @@
> >  #include "xe_guc_tlb_inval.h"
> >  #include "xe_mmio.h"
> >  #include "xe_pm.h"
> > +#include "xe_printk.h"
> >  #include "xe_tlb_inval.h"
> >  #include "xe_trace.h"
> >  
> > @@ -99,6 +100,11 @@ static void xe_tlb_inval_fence_timeout(struct work_struct *work)
> >  			fence->seqno, tlb_inval->seqno_recv);
> >  
> >  		timedout_seqno = fence->seqno;
> > +		if (!tlb_inval->timedout_seqno) {
> > +			tlb_inval->timedout_seqno = fence->seqno;
> > +			tlb_inval->timedout_inval_time = fence->inval_time;
> > +			tlb_inval->timedout_time = ktime_get();
> > +		}
> >  
> >  		fence->base.error = -ETIME;
> >  		xe_tlb_inval_fence_signal(fence);
> > @@ -227,6 +233,7 @@ void xe_tlb_inval_reset(struct xe_tlb_inval *tlb_inval)
> >  	else
> >  		pending_seqno = tlb_inval->seqno - 1;
> >  	WRITE_ONCE(tlb_inval->seqno_recv, pending_seqno);
> > +	tlb_inval->timedout_seqno = 0;
> >  
> >  	list_for_each_entry_safe(fence, next,
> >  				 &tlb_inval->pending_fences, link)
> > @@ -454,6 +461,18 @@ void xe_tlb_inval_done_handler(struct xe_tlb_inval *tlb_inval, int seqno)
> >  
> >  	WRITE_ONCE(tlb_inval->seqno_recv, seqno);
> >  
> > +	if (tlb_inval->timedout_seqno &&
> > +	    xe_tlb_inval_seqno_past(tlb_inval, tlb_inval->timedout_seqno)) {
> > +		ktime_t now = ktime_get();
> > +
> > +		xe_warn(xe,
> > +			"TLB invalidation late ack: seqno=%d recv=%d, request-to-ack=%lldms, timeout-to-ack=%lldms",
> > +			tlb_inval->timedout_seqno, seqno,
> > +			ktime_ms_delta(now, tlb_inval->timedout_inval_time),
> > +			ktime_ms_delta(now, tlb_inval->timedout_time));
> 
> Should this be some type SIGID message?
> 
> Matt
> 
> > +		tlb_inval->timedout_seqno = 0;
> > +	}
> > +
> >  	list_for_each_entry_safe(fence, next,
> >  				 &tlb_inval->pending_fences, link) {
> >  		trace_xe_tlb_inval_fence_recv(xe, fence);
> > diff --git a/drivers/gpu/drm/xe/xe_tlb_inval_types.h b/drivers/gpu/drm/xe/xe_tlb_inval_types.h
> > index d77be1aedc9..80d2019fa20 100644
> > --- a/drivers/gpu/drm/xe/xe_tlb_inval_types.h
> > +++ b/drivers/gpu/drm/xe/xe_tlb_inval_types.h
> > @@ -112,6 +112,23 @@ struct xe_tlb_inval {
> >  	 * @pending_lock: protects @pending_fences and updating @seqno_recv.
> >  	 */
> >  	spinlock_t pending_lock;
> > +	/**
> > +	 * @timedout_seqno: seqno of the most recent timed out TLB
> > +	 * invalidation, 0 if none. Used to measure how late the ack for a
> > +	 * timed out invalidation actually arrives. Protected by
> > +	 * @pending_lock.
> > +	 */
> > +	int timedout_seqno;
> > +	/**
> > +	 * @timedout_inval_time: request time of @timedout_seqno. Protected by
> > +	 * @pending_lock.
> > +	 */
> > +	ktime_t timedout_inval_time;
> > +	/**
> > +	 * @timedout_time: time @timedout_seqno was signaled with -ETIME.
> > +	 * Protected by @pending_lock.
> > +	 */
> > +	ktime_t timedout_time;
> >  	/**
> >  	 * @fence_tdr: schedules a delayed call to xe_tlb_fence_timeout after
> >  	 * the timeout interval is over.
> > -- 
> > 2.55.0
> >