[PATCH 13/26] RFC 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 Thomas, Joonas and Simona.

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: 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  | 12 ++++++++++++
 drivers/gpu/drm/xe/xe_vm.c       | 11 +++++++++++
 drivers/gpu/drm/xe/xe_vm_types.h |  6 ++++++
 3 files changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_eudebug.c b/drivers/gpu/drm/xe/xe_eudebug.c
index 9d87df75348b..980b5a1383ad 100644
--- a/drivers/gpu/drm/xe/xe_eudebug.c
+++ b/drivers/gpu/drm/xe/xe_eudebug.c
@@ -3074,6 +3074,18 @@ 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), 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 0f17bc8b627b..c23bb4547d66 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -999,6 +999,14 @@ static struct xe_vma *xe_vma_create(struct xe_vm *vm,
 			}
 
 			userptr->notifier_seq = LONG_MAX;
+#if IS_ENABLED(CONFIG_DRM_XE_EUDEBUG)
+			/*
+			 * 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);
+#endif
 		}
 
 		xe_vm_get(vm);
@@ -1023,6 +1031,9 @@ static void xe_vma_destroy_late(struct xe_vma *vma)
 		if (userptr->sg)
 			xe_hmm_userptr_free_sg(uvma);
 
+#if IS_ENABLED(CONFIG_DRM_XE_EUDEBUG)
+		put_task_struct(userptr->eudebug.task);
+#endif
 		/*
 		 * 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_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