Re: [PATCH 3/3] drm/xe/ggtt: invalidate engine GGTT TLBs for multi-queue GTs

[Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>]

On Fri, Aug 21, 2026 at 01:12:38PM +0530, tilak.tirumalesh.tangudu@intel.com wrote:
>From: Tangudu Tilak Tirumalesh <tilak.tirumalesh.tangudu@intel.com>
>
>Engines cache GGTT translations in their own TLBs, which the
>xe_tlb_inval_ggtt() does not touch.
>After a GGTT unmap the engines can still hit the stale translation and
>read the old page.
>
>Issue a FULL_INTRA_VF invalidation on GGTT unmap, gated on the GT
>having any multi-queue engine class.

NIT...probably good to keep the name consistent.
"Issue a INVAL_FULL (intra vf) invalidation...."?

>
>Assisted-by: Claude:claude-opus-4-8
>Signed-off-by: Tangudu Tilak Tirumalesh <tilak.tirumalesh.tangudu@intel.com>
>---
> drivers/gpu/drm/xe/xe_ggtt.c | 23 ++++++++++++++++++++++-
> 1 file changed, 22 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/gpu/drm/xe/xe_ggtt.c b/drivers/gpu/drm/xe/xe_ggtt.c
>index 3564345fd740..60eb9a3d29cc 100644
>--- a/drivers/gpu/drm/xe/xe_ggtt.c
>+++ b/drivers/gpu/drm/xe/xe_ggtt.c
>@@ -458,6 +458,7 @@ int xe_ggtt_init_early(struct xe_ggtt *ggtt)
> ALLOW_ERROR_INJECTION(xe_ggtt_init_early, ERRNO); /* See xe_pci_probe() */
>
> static void xe_ggtt_invalidate(struct xe_ggtt *ggtt);
>+static void xe_ggtt_invalidate_engine(struct xe_ggtt *ggtt);
>
> static void xe_ggtt_initial_clear(struct xe_ggtt *ggtt)
> {
>@@ -493,8 +494,11 @@ static void ggtt_node_remove(struct xe_ggtt_node *node)
> 			      xe_ggtt_node_size(node), use_scratch);
> 	drm_mm_remove_node(&node->base);
> 	node->base.size = 0;
>-	if (bound && node->invalidate_on_remove)
>+	if (bound && node->invalidate_on_remove) {
> 		xe_ggtt_invalidate(ggtt);
>+		/* Drain engine TLBs so a recycled range can't hit a stale entry. */
>+		xe_ggtt_invalidate_engine(ggtt);
>+	}
> 	mutex_unlock(&ggtt->lock);
>
> 	ggtt_node_fini(node);
>@@ -603,6 +607,23 @@ static void xe_ggtt_invalidate(struct xe_ggtt *ggtt)
> 	ggtt_invalidate_gt_tlb(ggtt->tile->media_gt);
> }
>
>+/*
>+ * Drain engine-side GGTT TLBs on teardown so a recycled range's next
>+ * occupant can't hit a predecessor's cached translation.
>+ */
>+static void xe_ggtt_invalidate_engine(struct xe_ggtt *ggtt)
>+{
>+	struct xe_gt *gt = ggtt->tile->primary_gt;
>+	int err;
>+
>+	if (!gt || !gt->info.multi_queue_engine_class_mask)
>+		return;
>+

As mentioned in other patch, probably good to abstract this into a
separate function with proper name and comment.

Niranjana

>+	err = xe_tlb_inval_ggtt_full(&gt->tlb_inval);
>+	xe_gt_WARN(gt, err, "Failed to invalidate engine GGTT TLBs (%pe)",
>+		   ERR_PTR(err));
>+}
>+
> /**
>  * xe_ggtt_shift_nodes() - Shift GGTT nodes to adjust for a change in usable address range.
>  * @ggtt: the &xe_ggtt struct instance
>-- 
>2.46.0
>