[RFC 5/7] drm/xe/vm: Deactivate madvise notifier on GPU touch

[Arvind Yadav <arvind.yadav@intel.com>]

MADVISE_AUTORESET notifier is only needed while VMA is CPU-only.
After GPU touch, the existing SVM notifier handles munmap.

Add 'active' flag to xe_madvise_notifier, cleared on first GPU touch.
The callback checks this flag and returns early when inactive.

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
---
 drivers/gpu/drm/xe/xe_svm.c        |  5 +++-
 drivers/gpu/drm/xe/xe_vm.h         |  6 ++--
 drivers/gpu/drm/xe/xe_vm_madvise.c | 46 ++++++++++++++++++++++++++++++
 drivers/gpu/drm/xe/xe_vm_madvise.h |  2 ++
 drivers/gpu/drm/xe/xe_vm_types.h   |  2 ++
 5 files changed, 58 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
index b9dbbb245779..3f09f5f6481f 100644
--- a/drivers/gpu/drm/xe/xe_svm.c
+++ b/drivers/gpu/drm/xe/xe_svm.c
@@ -21,6 +21,7 @@
 #include "xe_tile.h"
 #include "xe_ttm_vram_mgr.h"
 #include "xe_vm.h"
+#include "xe_vm_madvise.h"
 #include "xe_vm_types.h"
 #include "xe_vram_types.h"
 
@@ -1367,8 +1368,10 @@ int xe_svm_handle_pagefault(struct xe_vm *vm, struct xe_vma *vma,
 	lockdep_assert_held_write(&vm->lock);
 
 	/* Transition CPU-only -> GPU-touched before installing PTEs. */
-	if (xe_vma_has_cpu_autoreset_active(vma))
+	if (xe_vma_has_cpu_autoreset_active(vma)) {
 		xe_vma_gpu_touch(vma);
+		xe_vm_madvise_gpu_touch(vm, vma);
+	}
 
 retry:
 	need_vram = xe_vma_need_vram_for_atomic(vm->xe, vma, atomic);
diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
index 3dc549550c91..f353ab928e4c 100644
--- a/drivers/gpu/drm/xe/xe_vm.h
+++ b/drivers/gpu/drm/xe/xe_vm.h
@@ -426,12 +426,14 @@ void xe_vma_mem_attr_copy(struct xe_vma_mem_attr *to, struct xe_vma_mem_attr *fr
 
 /**
  * xe_vma_gpu_touch() - Mark VMA as GPU-touched
- * @vma: VMA to mark
+ * @vma: VMA to transition
  *
- * Clear XE_VMA_CPU_AUTORESET_ACTIVE. Must be done before first GPU PTE install.
+ * Clears CPU_AUTORESET_ACTIVE flag. Call xe_vm_madvise_gpu_touch() separately
+ * to deactivate the madvise notifier.
  */
 static inline void xe_vma_gpu_touch(struct xe_vma *vma)
 {
 	vma->gpuva.flags &= ~XE_VMA_CPU_AUTORESET_ACTIVE;
 }
+
 #endif
diff --git a/drivers/gpu/drm/xe/xe_vm_madvise.c b/drivers/gpu/drm/xe/xe_vm_madvise.c
index 4c0ffb100bcc..98663707d039 100644
--- a/drivers/gpu/drm/xe/xe_vm_madvise.c
+++ b/drivers/gpu/drm/xe/xe_vm_madvise.c
@@ -657,6 +657,9 @@ static bool xe_madvise_notifier_callback(struct mmu_interval_notifier *mni,
 	if (range->event != MMU_NOTIFY_UNMAP)
 		return true;
 
+	if (!atomic_read(&notifier->active))
+		return true;
+
 	/*
 	 * Best-effort: skip in non-blockable contexts to avoid building up work.
 	 * Correctness does not rely on this notifier - CPU_AUTORESET_ACTIVE flag
@@ -857,6 +860,7 @@ int xe_vm_madvise_register_notifier_range(struct xe_vm *vm, u64 start, u64 end)
 	notifier->vm = xe_vm_get(vm);
 	notifier->vma_start = start;
 	notifier->vma_end = end;
+	atomic_set(&notifier->active, 1);
 	INIT_LIST_HEAD(&notifier->list);
 
 	err = mmu_interval_notifier_insert(&notifier->mmu_notifier,
@@ -894,3 +898,45 @@ int xe_vm_madvise_register_notifier_range(struct xe_vm *vm, u64 start, u64 end)
 
 	return 0;
 }
+
+/**
+ * xe_vm_deactivate_madvise_notifier_for_range - Deactivate notifier for a range
+ * @vm: VM
+ * @start: Start address (page-aligned)
+ * @end: End address (page-aligned)
+ *
+ * Called when GPU touches a VMA - disables munmap processing for this range.
+ * Notifier remains registered but callback becomes a no-op until VM teardown.
+ */
+void xe_vm_deactivate_madvise_notifier_for_range(struct xe_vm *vm, u64 start, u64 end)
+{
+	struct xe_madvise_notifier *notifier;
+
+	/* Skip if madvise infrastructure not initialized */
+	if (!READ_ONCE(vm->svm.madvise_work.wq))
+		return;
+
+	mutex_lock(&vm->svm.madvise_notifiers.lock);
+	/* Deactivate overlapping notifiers (VMA splits may create multiple) */
+	list_for_each_entry(notifier, &vm->svm.madvise_notifiers.list, list) {
+		if (notifier->vma_start < end && notifier->vma_end > start)
+			atomic_set(&notifier->active, 0);
+	}
+	mutex_unlock(&vm->svm.madvise_notifiers.lock);
+}
+
+/**
+ * xe_vm_madvise_gpu_touch() - Deactivate madvise notifier on GPU touch
+ * @vm: VM
+ * @vma: VMA that was GPU-touched
+ *
+ * Deactivates the madvise notifier for this VMA's range after GPU touch.
+ * Call after xe_vma_gpu_touch() clears the CPU_AUTORESET_ACTIVE flag.
+ */
+void xe_vm_madvise_gpu_touch(struct xe_vm *vm, struct xe_vma *vma)
+{
+	if (vma->gpuva.flags & XE_VMA_MADV_AUTORESET)
+		xe_vm_deactivate_madvise_notifier_for_range(vm,
+							    xe_vma_start(vma),
+							    xe_vma_end(vma));
+}
diff --git a/drivers/gpu/drm/xe/xe_vm_madvise.h b/drivers/gpu/drm/xe/xe_vm_madvise.h
index ba9cd7912113..91417062a33e 100644
--- a/drivers/gpu/drm/xe/xe_vm_madvise.h
+++ b/drivers/gpu/drm/xe/xe_vm_madvise.h
@@ -19,5 +19,7 @@ int xe_vm_madvise_ioctl(struct drm_device *dev, void *data,
 int xe_vm_madvise_init(struct xe_vm *vm);
 void xe_vm_madvise_fini(struct xe_vm *vm);
 int xe_vm_madvise_register_notifier_range(struct xe_vm *vm, u64 start, u64 end);
+void xe_vm_deactivate_madvise_notifier_for_range(struct xe_vm *vm, u64 start, u64 end);
+void xe_vm_madvise_gpu_touch(struct xe_vm *vm, struct xe_vma *vma);
 
 #endif
diff --git a/drivers/gpu/drm/xe/xe_vm_types.h b/drivers/gpu/drm/xe/xe_vm_types.h
index eb978995000c..9cdae3492472 100644
--- a/drivers/gpu/drm/xe/xe_vm_types.h
+++ b/drivers/gpu/drm/xe/xe_vm_types.h
@@ -48,6 +48,8 @@ struct xe_madvise_notifier {
 	u64 vma_end;
 	/** @list: Link in vm->svm.madvise_notifiers.list */
 	struct list_head list;
+	/** @active: Cleared when GPU touches VMA to avoid callback overhead */
+	atomic_t active;
 };
 
 #if IS_ENABLED(CONFIG_DRM_XE_DEBUG)
-- 
2.43.0