[PATCH 13/26] RFC drm/xe/eudebug: userptr vm pread/pwrite

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

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 Thomas, Joonas and Simona.

v2: need to add offset into vma (Dominik)

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Dominik Grzegorzek <dominik.grzegorzek@intel.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Simona Vetter <simona@ffwll.ch>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
---
 drivers/gpu/drm/xe/xe_eudebug.c  | 13 +++++++++++++
 drivers/gpu/drm/xe/xe_vm.c       |  4 ++++
 drivers/gpu/drm/xe/xe_vm.h       | 28 +++++++++++++++++++++++++++-
 drivers/gpu/drm/xe/xe_vm_types.h |  6 ++++++
 4 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_eudebug.c b/drivers/gpu/drm/xe/xe_eudebug.c
index 9d87df75348b..8b29192ab110 100644
--- a/drivers/gpu/drm/xe/xe_eudebug.c
+++ b/drivers/gpu/drm/xe/xe_eudebug.c
@@ -3074,6 +3074,19 @@ static int xe_eudebug_vma_access(struct xe_vma *vma, u64 offset_in_vma,
 		xe_bo_put(bo);
 
 		return ret;
+	} else if (xe_vma_is_userptr(vma)) {
+		struct xe_userptr *userptr = &to_userptr_vma(vma)->userptr;
+
+		/*
+		 * XXX: 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 1cb21325d8dd..235ae2db5188 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -999,6 +999,8 @@ 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);
@@ -1023,6 +1025,8 @@ 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 notifer 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 23adb7442881..4334cf2b0d9d 100644
--- a/drivers/gpu/drm/xe/xe_vm.h
+++ b/drivers/gpu/drm/xe/xe_vm.h
@@ -274,9 +274,35 @@ static inline void vm_dbg(const struct drm_device *dev,
 			  const char *format, ...)
 { /* noop */ }
 #endif
-#endif
 
 struct xe_vm_snapshot *xe_vm_snapshot_capture(struct xe_vm *vm);
 void xe_vm_snapshot_capture_delayed(struct xe_vm_snapshot *snap);
 void xe_vm_snapshot_print(struct xe_vm_snapshot *snap, struct drm_printer *p);
 void xe_vm_snapshot_free(struct xe_vm_snapshot *snap);
+
+#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 557b047ebdd7..26176ccbcbbc 100644
--- a/drivers/gpu/drm/xe/xe_vm_types.h
+++ b/drivers/gpu/drm/xe/xe_vm_types.h
@@ -68,6 +68,12 @@ 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