Re: [PATCH v2 3/5] drm/xe/vf: Wait for default LRCs fixups before using

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

On Thu, Feb 19, 2026 at 12:16:49PM -0800, Matthew Brost wrote:
> On Thu, Feb 19, 2026 at 12:21:56AM +0100, Tomasz Lis wrote:
> > When a context is being created during save/restore, the LRC creation
> > needs to wait for GGTT address space to be shifted. But it also needs
> > to have fixed default LRCs. This is mandatory to avoid the situation
> > where LRC will be created based on data from before the fixups, but
> > reference within exec queue will be set too late for fixups.
> > 
> > This fixes an issue where contexts created during save/restore have
> > a large chance of having one unfixed LRC, due to the xe_lrc_create()
> > being synced for equal start to race with default LRC fixups.
> > 
> > Signed-off-by: Tomasz Lis <tomasz.lis@intel.com>
> 
> This is better than what is in place, so...
> Reviewed-by: Matthew Brost <matthew.brost@intel.com>

A little quick on this RB, see my comment here [1].

[1] https://patchwork.freedesktop.org/patch/705610/?series=161287&rev=2#comment_1298253

> 
> But I think we need to close on why my suggestion in the previous rev
> isn't fixing the issue (off list discussion). If we go this series, then

We still need to figure out why my previous suggestion doesn't work.

> my RB holds for future revs.
> 
> Matt 
> 
> > ---
> >  drivers/gpu/drm/xe/xe_exec_queue.c        |  2 +-
> >  drivers/gpu/drm/xe/xe_gt_sriov_vf.c       | 24 +++++++++++------------
> >  drivers/gpu/drm/xe/xe_gt_sriov_vf.h       |  2 +-
> >  drivers/gpu/drm/xe/xe_gt_sriov_vf_types.h |  4 ++--
> >  4 files changed, 15 insertions(+), 17 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_exec_queue.c b/drivers/gpu/drm/xe/xe_exec_queue.c
> > index e9396ad3390a..6eb561086e1c 100644
> > --- a/drivers/gpu/drm/xe/xe_exec_queue.c
> > +++ b/drivers/gpu/drm/xe/xe_exec_queue.c
> > @@ -309,7 +309,7 @@ static int __xe_exec_queue_init(struct xe_exec_queue *q, u32 exec_queue_flags)
> >  	for (i = 0; i < q->width; ++i) {
> >  		struct xe_lrc *lrc;
> >  
> > -		xe_gt_sriov_vf_wait_valid_ggtt(q->gt);
> > +		xe_gt_sriov_vf_wait_valid_default_lrc(q->gt);
> >  		lrc = xe_lrc_create(q->hwe, q->vm, q->replay_state,
> >  				    xe_lrc_ring_size(), q->msix_vec, flags);
> >  		if (IS_ERR(lrc)) {
> > diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_vf.c b/drivers/gpu/drm/xe/xe_gt_sriov_vf.c
> > index 527ded3c9c22..5ce06031018d 100644
> > --- a/drivers/gpu/drm/xe/xe_gt_sriov_vf.c
> > +++ b/drivers/gpu/drm/xe/xe_gt_sriov_vf.c
> > @@ -536,12 +536,6 @@ static int vf_get_ggtt_info(struct xe_gt *gt)
> >  	 */
> >  	xe_ggtt_shift_nodes(tile->mem.ggtt, start);
> >  
> > -	if (xe_sriov_vf_migration_supported(gt_to_xe(gt))) {
> > -		WRITE_ONCE(gt->sriov.vf.migration.ggtt_need_fixes, false);
> > -		smp_wmb();	/* Ensure above write visible before wake */
> > -		wake_up_all(&gt->sriov.vf.migration.wq);
> > -	}
> > -
> >  	return 0;
> >  }
> >  
> > @@ -844,6 +838,10 @@ static void xe_gt_sriov_vf_default_lrcs_hwsp_rebase(struct xe_gt *gt)
> >  
> >  	for_each_hw_engine(hwe, gt, id)
> >  		xe_default_lrc_update_memirq_regs_with_address(hwe);
> > +
> > +	WRITE_ONCE(gt->sriov.vf.migration.default_lrcs_need_fixes, false);
> > +	smp_wmb();	/* Ensure above write visible before wake */
> > +	wake_up_all(&gt->sriov.vf.migration.wq);

Then with [1], move this wakeup to vf_post_migration_fixups after all fixups.

Matt

> >  }
> >  
> >  static void vf_start_migration_recovery(struct xe_gt *gt)
> > @@ -858,7 +856,7 @@ static void vf_start_migration_recovery(struct xe_gt *gt)
> >  	    !gt->sriov.vf.migration.recovery_teardown) {
> >  		gt->sriov.vf.migration.recovery_queued = true;
> >  		WRITE_ONCE(gt->sriov.vf.migration.recovery_inprogress, true);
> > -		WRITE_ONCE(gt->sriov.vf.migration.ggtt_need_fixes, true);
> > +		WRITE_ONCE(gt->sriov.vf.migration.default_lrcs_need_fixes, true);
> >  		smp_wmb();	/* Ensure above writes visible before wake */
> >  
> >  		xe_guc_ct_wake_waiters(&gt->uc.guc.ct);
> > @@ -1303,7 +1301,7 @@ static void vf_post_migration_abort(struct xe_gt *gt)
> >  {
> >  	spin_lock_irq(&gt->sriov.vf.migration.lock);
> >  	WRITE_ONCE(gt->sriov.vf.migration.recovery_inprogress, false);
> > -	WRITE_ONCE(gt->sriov.vf.migration.ggtt_need_fixes, false);
> > +	WRITE_ONCE(gt->sriov.vf.migration.default_lrcs_need_fixes, false);
> >  	spin_unlock_irq(&gt->sriov.vf.migration.lock);
> >  
> >  	wake_up_all(&gt->sriov.vf.migration.wq);
> > @@ -1499,7 +1497,7 @@ bool xe_gt_sriov_vf_recovery_pending(struct xe_gt *gt)
> >  	return READ_ONCE(gt->sriov.vf.migration.recovery_inprogress);
> >  }
> >  
> > -static bool vf_valid_ggtt(struct xe_gt *gt)
> > +static bool vf_valid_default_lrc(struct xe_gt *gt)
> >  {
> >  	struct xe_memirq *memirq = &gt_to_tile(gt)->memirq;
> >  	bool irq_pending = xe_device_uses_memirq(gt_to_xe(gt)) &&
> > @@ -1507,17 +1505,17 @@ static bool vf_valid_ggtt(struct xe_gt *gt)
> >  
> >  	xe_gt_assert(gt, IS_SRIOV_VF(gt_to_xe(gt)));
> >  
> > -	if (irq_pending || READ_ONCE(gt->sriov.vf.migration.ggtt_need_fixes))
> > +	if (irq_pending || READ_ONCE(gt->sriov.vf.migration.default_lrcs_need_fixes))
> >  		return false;
> >  
> >  	return true;
> >  }
> >  
> >  /**
> > - * xe_gt_sriov_vf_wait_valid_ggtt() - VF wait for valid GGTT addresses
> > + * xe_gt_sriov_vf_wait_valid_default_lrc() - wait for valid GGTT refs in default LRCs
> >   * @gt: the &xe_gt
> >   */
> > -void xe_gt_sriov_vf_wait_valid_ggtt(struct xe_gt *gt)
> > +void xe_gt_sriov_vf_wait_valid_default_lrc(struct xe_gt *gt)
> >  {
> >  	int ret;
> >  
> > @@ -1526,7 +1524,7 @@ void xe_gt_sriov_vf_wait_valid_ggtt(struct xe_gt *gt)
> >  		return;
> >  
> >  	ret = wait_event_interruptible_timeout(gt->sriov.vf.migration.wq,
> > -					       vf_valid_ggtt(gt),
> > +					       vf_valid_default_lrc(gt),
> >  					       HZ * 5);
> >  	xe_gt_WARN_ON(gt, !ret);
> >  }
> > diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_vf.h b/drivers/gpu/drm/xe/xe_gt_sriov_vf.h
> > index 7d97189c2d3d..70232dc38f9a 100644
> > --- a/drivers/gpu/drm/xe/xe_gt_sriov_vf.h
> > +++ b/drivers/gpu/drm/xe/xe_gt_sriov_vf.h
> > @@ -39,6 +39,6 @@ void xe_gt_sriov_vf_print_config(struct xe_gt *gt, struct drm_printer *p);
> >  void xe_gt_sriov_vf_print_runtime(struct xe_gt *gt, struct drm_printer *p);
> >  void xe_gt_sriov_vf_print_version(struct xe_gt *gt, struct drm_printer *p);
> >  
> > -void xe_gt_sriov_vf_wait_valid_ggtt(struct xe_gt *gt);
> > +void xe_gt_sriov_vf_wait_valid_default_lrc(struct xe_gt *gt);
> >  
> >  #endif
> > diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_vf_types.h b/drivers/gpu/drm/xe/xe_gt_sriov_vf_types.h
> > index 4ef881b9b662..8be181bf3cf3 100644
> > --- a/drivers/gpu/drm/xe/xe_gt_sriov_vf_types.h
> > +++ b/drivers/gpu/drm/xe/xe_gt_sriov_vf_types.h
> > @@ -73,8 +73,8 @@ struct xe_gt_sriov_vf_migration {
> >  	bool recovery_queued;
> >  	/** @recovery_inprogress: VF post migration recovery in progress */
> >  	bool recovery_inprogress;
> > -	/** @ggtt_need_fixes: VF GGTT needs fixes */
> > -	bool ggtt_need_fixes;
> > +	/** @default_lrcs_need_fixes: GGTT refs within default LRCs need fixes */
> > +	bool default_lrcs_need_fixes;
> >  };
> >  
> >  /**
> > -- 
> > 2.25.1
> >