[PATCH 12/24] 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 Simona, Thomas and Joonas.

v2: need to add offset into vma (Dominik)
v3: move code into xe_userptr.c (Mika)

Cc: Simona Vetter <simona@ffwll.ch>
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>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
---
 drivers/gpu/drm/xe/xe_eudebug_vm.c | 16 +++++++++++++++
 drivers/gpu/drm/xe/xe_userptr.c    |  4 ++++
 drivers/gpu/drm/xe/xe_userptr.h    | 32 ++++++++++++++++++++++++++++++
 3 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 dd75227555ee..8485397cf9c6 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_userptr.c b/drivers/gpu/drm/xe/xe_userptr.c
index 6761005c0b90..ce7f30d2ccee 100644
--- a/drivers/gpu/drm/xe/xe_userptr.c
+++ b/drivers/gpu/drm/xe/xe_userptr.c
@@ -403,6 +403,8 @@ int xe_userptr_setup(struct xe_userptr_vma *uvma, unsigned long start,
 
 	userptr->pages.notifier_seq = LONG_MAX;
 
+	xe_eudebug_track_userptr_task(userptr);
+
 	return 0;
 }
 
@@ -411,6 +413,8 @@ void xe_userptr_remove(struct xe_userptr_vma *uvma)
 	struct xe_vm *vm = xe_vma_vm(&uvma->vma);
 	struct xe_userptr *userptr = &uvma->userptr;
 
+	xe_eudebug_untrack_userptr_task(userptr);
+
 	drm_gpusvm_free_pages(&vm->svm.gpusvm, &uvma->userptr.pages,
 			      xe_vma_size(&uvma->vma) >> PAGE_SHIFT);
 
diff --git a/drivers/gpu/drm/xe/xe_userptr.h b/drivers/gpu/drm/xe/xe_userptr.h
index 2a3cd1b5efbb..b0781618b3f4 100644
--- a/drivers/gpu/drm/xe/xe_userptr.h
+++ b/drivers/gpu/drm/xe/xe_userptr.h
@@ -95,6 +95,12 @@ 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
 };
 
 #if IS_ENABLED(CONFIG_DRM_GPUSVM)
@@ -133,4 +139,30 @@ 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
-- 
2.43.0