[PATCH i-g-t 4/5] lib/xe: add __xe_vm_bind_lr_sync() failable bind helper

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

Add __xe_vm_bind_lr_sync() which performs a synchronous LR VM bind and
returns an error code instead of asserting, allowing callers to handle
expected failures such as -ENOMEM or -ENOSPC from the dmem cgroup
controller.

Refactor xe_vm_bind_lr_sync() to delegate to the new helper and assert
on the result, preserving existing behaviour for callers that do not
need to inspect the error.

Assisted-by: GitHub Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 lib/xe/xe_ioctl.c | 79 ++++++++++++++++++++++++++++++++++++++---------
 lib/xe/xe_ioctl.h |  3 ++
 2 files changed, 67 insertions(+), 15 deletions(-)

diff --git a/lib/xe/xe_ioctl.c b/lib/xe/xe_ioctl.c
index ea3f2fcaa..9a0903bfb 100644
--- a/lib/xe/xe_ioctl.c
+++ b/lib/xe/xe_ioctl.c
@@ -822,40 +822,89 @@ void xe_vm_madvise(int fd, uint32_t vm, uint64_t addr, uint64_t range,
 }
 
 #define	BIND_SYNC_VAL	0x686868
-void xe_vm_bind_lr_sync(int fd, uint32_t vm, uint32_t bo, uint64_t offset,
-			uint64_t addr, uint64_t size, uint32_t flags)
+/**
+ * __xe_vm_bind_lr_sync() - Bind a BO into an LR VM, returning errors.
+ * @fd: xe device file descriptor.
+ * @vm: VM id (must have been created with %DRM_XE_VM_CREATE_FLAG_LR_MODE).
+ * @bo: GEM handle to bind.
+ * @offset: Offset within @bo.
+ * @addr: GPU virtual address to map at.
+ * @size: Size of the mapping.
+ * @flags: %DRM_XE_VM_BIND_FLAG_* flags.
+ *
+ * Like xe_vm_bind_lr_sync() but returns an error code instead of asserting,
+ * allowing callers to handle expected failures such as -%ENOMEM or -%ENOSPC
+ * from the dmem cgroup controller.
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int __xe_vm_bind_lr_sync(int fd, uint32_t vm, uint32_t bo, uint64_t offset,
+			 uint64_t addr, uint64_t size, uint32_t flags)
 {
-	volatile uint64_t *sync_addr = malloc(sizeof(*sync_addr));
+	uint64_t *sync_addr = malloc(sizeof(*sync_addr));
 	struct drm_xe_sync sync = {
 		.flags = DRM_XE_SYNC_FLAG_SIGNAL,
 		.type = DRM_XE_SYNC_TYPE_USER_FENCE,
-		.addr = to_user_pointer((uint64_t *)sync_addr),
+		.addr = to_user_pointer(sync_addr),
 		.timeline_value = BIND_SYNC_VAL,
 	};
+	int err;
 
-	igt_assert(!!sync_addr);
-	xe_vm_bind_async_flags(fd, vm, 0, bo, 0, addr, size, &sync, 1, flags);
-	if (*sync_addr != BIND_SYNC_VAL)
-		xe_wait_ufence(fd, (uint64_t *)sync_addr, BIND_SYNC_VAL, 0, NSEC_PER_SEC * 10);
+	if (!sync_addr)
+		return -ENOMEM;
+
+	WRITE_ONCE(*sync_addr, 0);
+	err = __xe_vm_bind(fd, vm, 0, bo, offset, addr, size,
+			   DRM_XE_VM_BIND_OP_MAP, flags, &sync, 1, 0,
+			   DEFAULT_PAT_INDEX, 0);
+	if (err) {
+		free(sync_addr);
+		return err;
+	}
+
+	if (READ_ONCE(*sync_addr) != BIND_SYNC_VAL)
+		xe_wait_ufence(fd, sync_addr, BIND_SYNC_VAL, 0,
+			       NSEC_PER_SEC * 10);
 	/* Only free if the wait succeeds */
-	free((void *)sync_addr);
+	free(sync_addr);
+	return 0;
+}
+
+/**
+ * xe_vm_bind_lr_sync() - Bind a BO into an LR VM, asserting on error.
+ * @fd: xe device file descriptor.
+ * @vm: VM id (must have been created with %DRM_XE_VM_CREATE_FLAG_LR_MODE).
+ * @bo: GEM handle to bind.
+ * @offset: Offset within @bo.
+ * @addr: GPU virtual address to map at.
+ * @size: Size of the mapping.
+ * @flags: %DRM_XE_VM_BIND_FLAG_* flags.
+ *
+ * Delegates to __xe_vm_bind_lr_sync() and asserts that the operation
+ * succeeds.  Use __xe_vm_bind_lr_sync() directly when the caller needs to
+ * handle expected failures such as -%ENOMEM or -%ENOSPC.
+ */
+void xe_vm_bind_lr_sync(int fd, uint32_t vm, uint32_t bo, uint64_t offset,
+			uint64_t addr, uint64_t size, uint32_t flags)
+{
+	igt_assert_eq(__xe_vm_bind_lr_sync(fd, vm, bo, offset, addr, size, flags), 0);
 }
 
 void xe_vm_unbind_lr_sync(int fd, uint32_t vm, uint64_t offset,
 			  uint64_t addr, uint64_t size)
 {
-	volatile uint64_t *sync_addr = malloc(sizeof(*sync_addr));
+	uint64_t *sync_addr = malloc(sizeof(*sync_addr));
 	struct drm_xe_sync sync = {
 		.flags = DRM_XE_SYNC_FLAG_SIGNAL,
 		.type = DRM_XE_SYNC_TYPE_USER_FENCE,
-		.addr = to_user_pointer((uint64_t *)sync_addr),
+		.addr = to_user_pointer(sync_addr),
 		.timeline_value = BIND_SYNC_VAL,
 	};
 
 	igt_assert(!!sync_addr);
-	*sync_addr = 0;
+	WRITE_ONCE(*sync_addr, 0);
 	xe_vm_unbind_async(fd, vm, 0, 0, addr, size, &sync, 1);
-	if (*sync_addr != BIND_SYNC_VAL)
-		xe_wait_ufence(fd, (uint64_t *)sync_addr, BIND_SYNC_VAL, 0, NSEC_PER_SEC * 10);
-	free((void *)sync_addr);
+	if (READ_ONCE(*sync_addr) != BIND_SYNC_VAL)
+		xe_wait_ufence(fd, sync_addr, BIND_SYNC_VAL, 0, NSEC_PER_SEC * 10);
+	free(sync_addr);
 }
diff --git a/lib/xe/xe_ioctl.h b/lib/xe/xe_ioctl.h
index b62d259fd..7f899ea93 100644
--- a/lib/xe/xe_ioctl.h
+++ b/lib/xe/xe_ioctl.h
@@ -114,6 +114,9 @@ int xe_vm_vma_attrs(int fd, struct drm_xe_vm_query_mem_range_attr *vmas_attr,
 struct drm_xe_mem_range_attr
 *xe_vm_get_mem_attr_values_in_range(int fd, uint32_t vm, uint64_t start,
 				    uint64_t range, uint32_t *num_ranges);
+int  __xe_vm_bind_lr_sync(int fd, uint32_t vm, uint32_t bo,
+			  uint64_t offset, uint64_t addr,
+			  uint64_t size, uint32_t flags);
 void xe_vm_bind_lr_sync(int fd, uint32_t vm, uint32_t bo,
 			uint64_t offset, uint64_t addr,
 			uint64_t size, uint32_t flags);
-- 
2.53.0