[RFC v3 3/7] drm/xe/svm: Clear CPU_AUTORESET_ACTIVE on first GPU fault

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

CPU address mirror VMAs start with cpu_autoreset_active set, indicating
they are still CPU-only.

Clear cpu_autoreset_active after successful fault handling. A successful
return means the fault address already has a valid GPU mapping or PTEs
were installed. Prefetch faults that do not establish a mapping return an
error and do not transition the state.

v2:
  - Move xe_vma_gpu_touch() to the success path in
    xe_svm_handle_pagefault() so prefetch faults that find no range do
    not transition the state. (Matt)
  - Add xe_vma_gpu_touch() helper in xe_vm.h and use
    vma->cpu_autoreset_active instead of vma->gpuva.flags. (Matt)

v3:
  - Drop lockdep_assert_held_write from xe_svm_handle_pagefault. (Matt)
  - Re-fetch the VMA in xe_pagefault_service() before clearing state.
  - Move gpu_touch from xe_svm_handle_pagefault to xe_pagefault_service
    (Matt)

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_pagefault.c | 10 +++++++++-
 drivers/gpu/drm/xe/xe_vm.h        | 13 +++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_pagefault.c b/drivers/gpu/drm/xe/xe_pagefault.c
index dd3c068e1a39..f64d3df08261 100644
--- a/drivers/gpu/drm/xe/xe_pagefault.c
+++ b/drivers/gpu/drm/xe/xe_pagefault.c
@@ -215,8 +215,16 @@ static int xe_pagefault_service(struct xe_pagefault *pf)
 		err = xe_pagefault_handle_vma(gt, vma, atomic);
 
 unlock_vm:
-	if (!err)
+	if (!err) {
+		/* Re-fetch, fault handling may have replaced the VMA. */
+		vma = xe_vm_find_vma_by_addr(vm, pf->consumer.page_addr);
 		vm->usm.last_fault_vma = vma;
+
+		/* First successful GPU fault ends CPU-only state. */
+		if (vma && xe_vma_is_cpu_addr_mirror(vma) &&
+		    xe_vma_has_cpu_autoreset_active(vma))
+			xe_vma_gpu_touch(vma);
+	}
 	up_write(&vm->lock);
 	xe_vm_put(vm);
 
diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
index 0dd201cce968..0ad704b05687 100644
--- a/drivers/gpu/drm/xe/xe_vm.h
+++ b/drivers/gpu/drm/xe/xe_vm.h
@@ -450,4 +450,17 @@ static inline struct drm_exec *xe_vm_validation_exec(struct xe_vm *vm)
 	((READ_ONCE(tile_present) & ~READ_ONCE(tile_invalidated)) & BIT((tile)->id))
 
 void xe_vma_mem_attr_copy(struct xe_vma_mem_attr *to, struct xe_vma_mem_attr *from);
+
+/**
+ * xe_vma_gpu_touch() - Mark a VMA as no longer CPU-only
+ * @vma: VMA to update
+ *
+ * Clear cpu_autoreset_active after the first successful GPU fault-in.
+ * Caller must hold vm->lock in write mode.
+ */
+static inline void xe_vma_gpu_touch(struct xe_vma *vma)
+{
+	lockdep_assert_held_write(&xe_vma_vm(vma)->lock);
+	vma->cpu_autoreset_active = false;
+}
 #endif
-- 
2.43.0