[PATCH] drm/xe: Skip media GT TLB invalidation when VM has no queues mapped

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

If no exec queues from a VM are mapped on the media GT, issuing a
PPGTT TLB invalidation for that GT requires an rc6 wake which is
expensive.

Skip the media GT TLB invalidation when the VM has no exec queues
mapped on it. If TLB invalidations are already in-flight on that GT
we can't break fence ordering, so issue a dummy GGTT invalidation
instead to maintain seqno ordering.

This optimization is particularly impactful for SVM workloads which
may or may not use the media GT. Average TLB invalidation time drops
from ~75us to ~18us in such benchmarks.

Assisted-by: GitHub Copilot:claude-sonnet-4.6 # Documentation only.
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
 drivers/gpu/drm/xe/xe_guc_tlb_inval.c | 43 +++++++++++++++++++++++++--
 1 file changed, 41 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_guc_tlb_inval.c b/drivers/gpu/drm/xe/xe_guc_tlb_inval.c
index ced58f46f846..20c34469d9a5 100644
--- a/drivers/gpu/drm/xe/xe_guc_tlb_inval.c
+++ b/drivers/gpu/drm/xe/xe_guc_tlb_inval.c
@@ -205,14 +205,53 @@ static int send_tlb_inval_asid_ppgtt(struct xe_tlb_inval *tlb_inval, u32 seqno,
 				     struct drm_suballoc *prl_sa)
 {
 	struct xe_guc *guc = tlb_inval->private;
+	struct xe_device *xe = guc_to_xe(guc);
+	struct xe_gt *gt = guc_to_gt(guc);
+	struct xe_vm *vm;
+	int err = 0, id = guc_to_gt(guc)->info.id;
 
 	lockdep_assert_held(&tlb_inval->seqno_lock);
 
 	if (guc_to_xe(guc)->info.force_execlist)
 		return -ECANCELED;
 
-	return send_tlb_inval_ppgtt(guc, seqno, start, end, asid,
-				    XE_GUC_TLB_INVAL_PAGE_SELECTIVE, prl_sa);
+	if (!xe_gt_is_media_type(gt))
+		return send_tlb_inval_ppgtt(guc, seqno, start, end, asid,
+					    XE_GUC_TLB_INVAL_PAGE_SELECTIVE,
+					    prl_sa);
+
+	/* Try to skip media GT TLB invalidations */
+
+	vm = xe_device_asid_to_vm(xe, asid);
+	if (IS_ERR(vm))
+		return PTR_ERR(vm);
+
+	down_read(&vm->exec_queues.lock);
+
+	if (!vm->exec_queues.count[id]) {
+		/*
+		 * We can't break fence ordering for TLB invalidation jobs, if
+		 * TLB invalidations are inflight issue a dummy invalidation to
+		 * maintain ordering. Nor can we move safely the seqno_recv when
+		 * returning -ECANCELED if TLB invalidations are in flight. Use
+		 * GGTT invalidation as dummy invalidation given ASID
+		 * invalidations are unsupported here.
+		 */
+		if (xe_tlb_inval_idle(tlb_inval))
+			err = -ECANCELED;
+		else
+			err = send_tlb_inval_ggtt(tlb_inval, seqno);
+		goto err_unlock;
+	}
+
+	err = send_tlb_inval_ppgtt(guc, seqno, start, end, asid,
+				   XE_GUC_TLB_INVAL_PAGE_SELECTIVE, prl_sa);
+
+err_unlock:
+	up_read(&vm->exec_queues.lock);
+	xe_vm_put(vm);
+
+	return err;
 }
 
 static int send_tlb_inval_ctx_ppgtt(struct xe_tlb_inval *tlb_inval, u32 seqno,
-- 
2.34.1