[PATCH 09/15] drm/xe/eudebug: userptr vm pread/pwrite

[Mika Kuoppala]

Implement debugger vm access for userptrs.

When bind is done, take ref to current task so that
we know from which vm the address was bound. Then during
debugger pread/pwrite we use this target task as
parameter to access the debuggee vm with access_process_vm().

This is based on suggestions from Simona, Thomas and Joonas.

v2: need to add offset into vma (Dominik)

Cc: Simona Vetter <simona at ffwll.ch>
Cc: Matthew Brost <matthew.brost at intel.com>
Cc: Andrzej Hajda <andrzej.hajda at intel.com>
Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Cc: Dominik Grzegorzek <dominik.grzegorzek at intel.com>
Cc: Christian König <christian.koenig at amd.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
---
 drivers/gpu/drm/xe/xe_eudebug_vm.c | 16 ++++++++++++++++
 drivers/gpu/drm/xe/xe_vm.c         |  4 ++++
 drivers/gpu/drm/xe/xe_vm.h         | 26 ++++++++++++++++++++++++++
 drivers/gpu/drm/xe/xe_vm_types.h   |  6 ++++++
 4 files changed, 52 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_eudebug_vm.c b/drivers/gpu/drm/xe/xe_eudebug_vm.c
index 6392482683f9..6799dbfe71f1 100644
--- a/drivers/gpu/drm/xe/xe_eudebug_vm.c
+++ b/drivers/gpu/drm/xe/xe_eudebug_vm.c
@@ -51,6 +51,22 @@ static int xe_eudebug_vma_access(struct xe_vma *vma,
 		xe_bo_put(bo);
 
 		return ret;
+	} else if (xe_vma_is_userptr(vma)) {
+		struct xe_userptr *userptr = &to_userptr_vma(vma)->userptr;
+
+		if (XE_WARN_ON(!userptr->eudebug.task))
+			return -EINVAL;
+
+		/*
+		 * access_remote_vm() would fit as userptr notifier has
+		 * mm ref so we would not need to carry task ref at all.
+		 * But access_remote_vm is not exported. access_process_vm()
+		 * is exported so use it instead.
+		 */
+		return access_process_vm(userptr->eudebug.task,
+					 xe_vma_userptr(vma) + offset_in_vma,
+					 buf, bytes,
+					 write ? FOLL_WRITE : 0);
 	}
 
 	return -EINVAL;
diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index 7787c442892a..ce854ebc0aee 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -1264,6 +1264,8 @@ static struct xe_vma *xe_vma_create(struct xe_vm *vm,
 			}
 
 			userptr->notifier_seq = LONG_MAX;
+
+			xe_eudebug_track_userptr_task(userptr);
 		}
 
 		xe_vm_get(vm);
@@ -1288,6 +1290,8 @@ static void xe_vma_destroy_late(struct xe_vma *vma)
 		if (userptr->sg)
 			xe_hmm_userptr_free_sg(uvma);
 
+		xe_eudebug_untrack_userptr_task(userptr);
+
 		/*
 		 * Since userptr pages are not pinned, we can't remove
 		 * the notifier until we're sure the GPU is not accessing
diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
index 3475a118f666..8c28ba095397 100644
--- a/drivers/gpu/drm/xe/xe_vm.h
+++ b/drivers/gpu/drm/xe/xe_vm.h
@@ -401,4 +401,30 @@ static inline void xe_vma_userptr_force_invalidate(struct xe_userptr_vma *uvma)
 {
 }
 #endif
+
+#if IS_ENABLED(CONFIG_DRM_XE_EUDEBUG)
+static inline void xe_eudebug_track_userptr_task(struct xe_userptr *userptr)
+{
+	/*
+	 * We could use the mm which is on notifier. But
+	 * the access_remote_vm() is not exported. Thus
+	 * we get reference to task for access_process_vm()
+	 */
+	userptr->eudebug.task = get_task_struct(current);
+}
+
+static inline void xe_eudebug_untrack_userptr_task(struct xe_userptr *userptr)
+{
+	put_task_struct(userptr->eudebug.task);
+}
+#else
+static inline void xe_eudebug_track_userptr_task(struct xe_userptr *userptr)
+{
+}
+
+static inline void xe_eudebug_untrack_userptr_task(struct xe_userptr *userptr)
+{
+}
+#endif /* CONFIG_DRM_XE_EUDEBUG */
+
 #endif
diff --git a/drivers/gpu/drm/xe/xe_vm_types.h b/drivers/gpu/drm/xe/xe_vm_types.h
index e20f8341d5e9..cbf8d4f95afc 100644
--- a/drivers/gpu/drm/xe/xe_vm_types.h
+++ b/drivers/gpu/drm/xe/xe_vm_types.h
@@ -76,6 +76,12 @@ struct xe_userptr {
 #if IS_ENABLED(CONFIG_DRM_XE_USERPTR_INVAL_INJECT)
 	u32 divisor;
 #endif
+
+#if IS_ENABLED(CONFIG_DRM_XE_EUDEBUG)
+	struct {
+		struct task_struct *task;
+	} eudebug;
+#endif
 };
 
 struct xe_vma {
-- 
2.43.0