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

Mika Kuoppala mika.kuoppala at linux.intel.com
Fri Dec 20 11:31:08 UTC 2024


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 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>
Cc: Simona Vetter <simona at ffwll.ch>
Signed-off-by: Mika Kuoppala <mika.kuoppala at 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



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