[PATCH v3 4/4] drm/xe/userptr: Defer Waiting for TLB invalidation to the second pass if possible

Thomas Hellström
2026-03-03T13:34:57Z

Now that the two-pass notifier flow uses xe_vma_userptr_do_inval() for
the fence-wait + TLB-invalidate work, extend it to support a further
deferred TLB wait:

- xe_vma_userptr_do_inval(): when the embedded finish handle is free,
submit the TLB invalidation asynchronously (xe_vm_invalidate_vma_submit)
and return &userptr->finish so the mmu_notifier core schedules a third
pass. When the handle is occupied by a concurrent invalidation, fall
back to the synchronous xe_vm_invalidate_vma() path.

- xe_vma_userptr_complete_tlb_inval(): new helper called from
invalidate_finish when tlb_inval_submitted is set. Waits for the
previously submitted batch and unmaps the gpusvm pages.

xe_vma_userptr_invalidate_finish() dispatches between the two helpers
via tlb_inval_submitted, making the three possible flows explicit:

pass1 (fences pending) -> invalidate_finish -> do_inval (sync TLB)
pass1 (fences done) -> do_inval -> invalidate_finish
-> complete_tlb_inval (deferred TLB)
pass1 (finish occupied) -> do_inval (sync TLB, inline)

In multi-GPU scenarios this allows TLB flushes to be submitted on all
GPUs in one pass before any of them are waited on.

Also adds xe_vm_invalidate_vma_submit() which submits the TLB range
invalidation without blocking, populating a xe_tlb_inval_batch that
the caller waits on separately.

v3:
- Add locking asserts and notifier state asserts (Matt Brost)
- Update the locking documentation of the notifier
state members (Matt Brost)
- Remove unrelated code formatting changes (Matt Brost)

Assisted-by: GitHub Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
drivers/gpu/drm/xe/xe_userptr.c | 63 ++++++++++++++++++++++++++++-----
drivers/gpu/drm/xe/xe_userptr.h | 17 +++++++++
drivers/gpu/drm/xe/xe_vm.c | 38 +++++++++++++++-----
drivers/gpu/drm/xe/xe_vm.h | 2 ++
4 files changed, 104 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_userptr.c b/drivers/gpu/drm/xe/xe_userptr.c
index 37032b8125a6..6761005c0b90 100644
--- a/drivers/gpu/drm/xe/xe_userptr.c
+++ b/drivers/gpu/drm/xe/xe_userptr.c
@@ -8,6 +8,7 @@

#include <linux/mm.h>

+#include "xe_tlb_inval.h"
#include "xe_trace_bo.h"

static void xe_userptr_assert_in_notifier(struct xe_vm *vm)
@@ -81,8 +82,8 @@ int xe_vma_userptr_pin_pages(struct xe_userptr_vma *uvma)
&ctx);
}

-static void xe_vma_userptr_do_inval(struct xe_vm *vm, struct xe_userptr_vma *uvma,
- bool is_deferred)
+static struct mmu_interval_notifier_finish *
+xe_vma_userptr_do_inval(struct xe_vm *vm, struct xe_userptr_vma *uvma, bool is_deferred)
{
struct xe_userptr *userptr = &uvma->userptr;
struct xe_vma *vma = &uvma->vma;
@@ -93,6 +94,8 @@ static void xe_vma_userptr_do_inval(struct xe_vm *vm, struct xe_userptr_vma *uvm
long err;

xe_userptr_assert_in_notifier(vm);
+ if (is_deferred)
+ xe_assert(vm->xe, userptr->finish_inuse && !userptr->tlb_inval_submitted);

err = dma_resv_wait_timeout(xe_vm_resv(vm),
DMA_RESV_USAGE_BOOKKEEP,
@@ -100,6 +103,19 @@ static void xe_vma_userptr_do_inval(struct xe_vm *vm, struct xe_userptr_vma *uvm
XE_WARN_ON(err <= 0);

if (xe_vm_in_fault_mode(vm) && userptr->initial_bind) {
+ if (!userptr->finish_inuse) {
+ /*
+ * Defer the TLB wait to an extra pass so the caller
+ * can pipeline TLB flushes across GPUs before waiting
+ * on any of them.
+ */
+ xe_assert(vm->xe, !userptr->tlb_inval_submitted);
+ userptr->finish_inuse = true;
+ userptr->tlb_inval_submitted = true;
+ err = xe_vm_invalidate_vma_submit(vma, &userptr->inval_batch);
+ XE_WARN_ON(err);
+ return &userptr->finish;
+ }
err = xe_vm_invalidate_vma(vma);
XE_WARN_ON(err);
}
@@ -108,6 +124,28 @@ static void xe_vma_userptr_do_inval(struct xe_vm *vm, struct xe_userptr_vma *uvm
userptr->finish_inuse = false;
drm_gpusvm_unmap_pages(&vm->svm.gpusvm, &uvma->userptr.pages,
xe_vma_size(vma) >> PAGE_SHIFT, &ctx);
+ return NULL;
+}
+
+static void
+xe_vma_userptr_complete_tlb_inval(struct xe_vm *vm, struct xe_userptr_vma *uvma)
+{
+ struct xe_userptr *userptr = &uvma->userptr;
+ struct xe_vma *vma = &uvma->vma;
+ struct drm_gpusvm_ctx ctx = {
+ .in_notifier = true,
+ .read_only = xe_vma_read_only(vma),
+ };
+
+ xe_userptr_assert_in_notifier(vm);
+ xe_assert(vm->xe, userptr->finish_inuse);
+ xe_assert(vm->xe, userptr->tlb_inval_submitted);
+
+ xe_tlb_inval_batch_wait(&userptr->inval_batch);
+ userptr->tlb_inval_submitted = false;
+ userptr->finish_inuse = false;
+ drm_gpusvm_unmap_pages(&vm->svm.gpusvm, &uvma->userptr.pages,
+ xe_vma_size(vma) >> PAGE_SHIFT, &ctx);
}

static struct mmu_interval_notifier_finish *
@@ -153,11 +191,10 @@ xe_vma_userptr_invalidate_pass1(struct xe_vm *vm, struct xe_userptr_vma *uvma)
* If it's already in use, or all fences are already signaled,
* proceed directly to invalidation without deferring.
*/
- if (signaled || userptr->finish_inuse) {
- xe_vma_userptr_do_inval(vm, uvma, false);
- return NULL;
- }
+ if (signaled || userptr->finish_inuse)
+ return xe_vma_userptr_do_inval(vm, uvma, false);

+ /* Defer: the notifier core will call invalidate_finish once done. */
userptr->finish_inuse = true;

return &userptr->finish;
@@ -205,7 +242,15 @@ static void xe_vma_userptr_invalidate_finish(struct mmu_interval_notifier_finish
xe_vma_start(vma), xe_vma_size(vma));

down_write(&vm->svm.gpusvm.notifier_lock);
- xe_vma_userptr_do_inval(vm, uvma, true);
+ /*
+ * If a TLB invalidation was previously submitted (deferred from the
+ * synchronous pass1 fallback), wait for it and unmap pages.
+ * Otherwise, fences have now completed: invalidate the TLB and unmap.
+ */
+ if (uvma->userptr.tlb_inval_submitted)
+ xe_vma_userptr_complete_tlb_inval(vm, uvma);
+ else
+ xe_vma_userptr_do_inval(vm, uvma, true);
up_write(&vm->svm.gpusvm.notifier_lock);
trace_xe_vma_userptr_invalidate_complete(vma);
}
@@ -243,7 +288,9 @@ void xe_vma_userptr_force_invalidate(struct xe_userptr_vma *uvma)

finish = xe_vma_userptr_invalidate_pass1(vm, uvma);
if (finish)
- xe_vma_userptr_do_inval(vm, uvma, true);
+ finish = xe_vma_userptr_do_inval(vm, uvma, true);
+ if (finish)
+ xe_vma_userptr_complete_tlb_inval(vm, uvma);
}
#endif

diff --git a/drivers/gpu/drm/xe/xe_userptr.h b/drivers/gpu/drm/xe/xe_userptr.h
index e1830c2f5fd2..2a3cd1b5efbb 100644
--- a/drivers/gpu/drm/xe/xe_userptr.h
+++ b/drivers/gpu/drm/xe/xe_userptr.h
@@ -14,6 +14,8 @@

#include <drm/drm_gpusvm.h>

+#include "xe_tlb_inval_types.h"
+
struct xe_vm;
struct xe_vma;
struct xe_userptr_vma;
@@ -63,12 +65,27 @@ struct xe_userptr {
* alternatively by the same lock in read mode *and* the vm resv held.
*/
struct mmu_interval_notifier_finish finish;
+ /**
+ * @inval_batch: TLB invalidation batch for deferred completion.
+ * Stores an in-flight TLB invalidation submitted during a two-pass
+ * notifier so the wait can be deferred to a subsequent pass, allowing
+ * multiple GPUs to be signalled before any of them are waited on.
+ * Protected using the same locking as @finish.
+ */
+ struct xe_tlb_inval_batch inval_batch;
/**
* @finish_inuse: Whether @finish is currently in use by an in-progress
* two-pass invalidation.
* Protected using the same locking as @finish.
*/
bool finish_inuse;
+ /**
+ * @tlb_inval_submitted: Whether a TLB invalidation has been submitted
+ * via @inval_batch and is pending completion. When set, the next pass
+ * must call xe_tlb_inval_batch_wait() before reusing @inval_batch.
+ * Protected using the same locking as @finish.
+ */
+ bool tlb_inval_submitted;
/**
* @initial_bind: user pointer has been bound at least once.
* write: vm->svm.gpusvm.notifier_lock in read mode and vm->resv held.
diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index a3c2e8cefec7..fdad9329dfb4 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -3967,20 +3967,23 @@ void xe_vm_unlock(struct xe_vm *vm)
}

/**
- * xe_vm_invalidate_vma - invalidate GPU mappings for VMA without a lock
+ * xe_vm_invalidate_vma_submit - Submit a job to invalidate GPU mappings for
+ * VMA.
* @vma: VMA to invalidate
+ * @batch: TLB invalidation batch to populate; caller must later call
+ * xe_tlb_inval_batch_wait() on it to wait for completion
*
* Walks a list of page tables leaves which it memset the entries owned by this
- * VMA to zero, invalidates the TLBs, and block until TLBs invalidation is
- * complete.
+ * VMA to zero, invalidates the TLBs, but doesn't block waiting for TLB flush
+ * to complete, but instead populates @batch which can be waited on using
+ * xe_tlb_inval_batch_wait().
*
* Returns 0 for success, negative error code otherwise.
*/
-int xe_vm_invalidate_vma(struct xe_vma *vma)
+int xe_vm_invalidate_vma_submit(struct xe_vma *vma, struct xe_tlb_inval_batch *batch)
{
struct xe_device *xe = xe_vma_vm(vma)->xe;
struct xe_vm *vm = xe_vma_vm(vma);
- struct xe_tlb_inval_batch batch;
struct xe_tile *tile;
u8 tile_mask = 0;
int ret = 0;
@@ -4023,14 +4026,33 @@ int xe_vm_invalidate_vma(struct xe_vma *vma)

ret = xe_tlb_inval_range_tilemask_submit(xe, xe_vma_vm(vma)->usm.asid,
xe_vma_start(vma), xe_vma_end(vma),
- tile_mask, &batch);
+ tile_mask, batch);

/* WRITE_ONCE pairs with READ_ONCE in xe_vm_has_valid_gpu_mapping() */
WRITE_ONCE(vma->tile_invalidated, vma->tile_mask);
+ return ret;
+}
+
+/**
+ * xe_vm_invalidate_vma - invalidate GPU mappings for VMA without a lock
+ * @vma: VMA to invalidate
+ *
+ * Walks a list of page tables leaves which it memset the entries owned by this
+ * VMA to zero, invalidates the TLBs, and block until TLBs invalidation is
+ * complete.
+ *
+ * Returns 0 for success, negative error code otherwise.
+ */
+int xe_vm_invalidate_vma(struct xe_vma *vma)
+{
+ struct xe_tlb_inval_batch batch;
+ int ret;

- if (!ret)
- xe_tlb_inval_batch_wait(&batch);
+ ret = xe_vm_invalidate_vma_submit(vma, &batch);
+ if (ret)
+ return ret;

+ xe_tlb_inval_batch_wait(&batch);
return ret;
}

diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
index 62f4b6fec0bc..0bc7ed23eeae 100644
--- a/drivers/gpu/drm/xe/xe_vm.h
+++ b/drivers/gpu/drm/xe/xe_vm.h
@@ -242,6 +242,8 @@ struct dma_fence *xe_vm_range_unbind(struct xe_vm *vm,

int xe_vm_invalidate_vma(struct xe_vma *vma);

+int xe_vm_invalidate_vma_submit(struct xe_vma *vma, struct xe_tlb_inval_batch *batch);
+
int xe_vm_validate_protected(struct xe_vm *vm);

static inline void xe_vm_queue_rebind_worker(struct xe_vm *vm)
--
2.53.0