[PATCH i-g-t 1/4] lib/xe: add xe_vm_restart ioctl helper

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

Add DRM_XE_VM_RESTART (ioctl 0x10) and struct drm_xe_vm_restart to the
Xe DRM UAPI header, taken from the xe_event kernel branch.

Add DRM_XE_VM_CREATE_FLAG_RESTARTABLE (bit 4) to allow VMs to opt in to
the restart mechanism.

Add __xe_vm_restart() (failable, with bounded EAGAIN retry) and
xe_vm_restart() (asserting wrapper) to lib/xe/xe_ioctl.  Both take an
optional CLOCK_MONOTONIC timestamp_ns which is forwarded to the IOCTL so
the driver can log event-to-restart latency.

Assisted-by: GitHub Copilot:claude-sonnet-4.6
---
 include/drm-uapi/xe_drm.h | 40 +++++++++++++++++++++++++++++++++++
 lib/xe/xe_ioctl.c         | 44 +++++++++++++++++++++++++++++++++++++++
 lib/xe/xe_ioctl.h         |  2 ++
 3 files changed, 86 insertions(+)

diff --git a/include/drm-uapi/xe_drm.h b/include/drm-uapi/xe_drm.h
index 5a96a7910..43b65b1d9 100644
--- a/include/drm-uapi/xe_drm.h
+++ b/include/drm-uapi/xe_drm.h
@@ -84,6 +84,7 @@ extern "C" {
  *  - &DRM_IOCTL_XE_MADVISE
  *  - &DRM_IOCTL_XE_VM_QUERY_MEM_RANGE_ATTRS
  *  - &DRM_IOCTL_XE_VM_GET_PROPERTY
+ *  - &DRM_IOCTL_XE_VM_RESTART
  */
 
 /*
@@ -109,6 +110,7 @@ extern "C" {
 #define DRM_XE_VM_QUERY_MEM_RANGE_ATTRS	0x0d
 #define DRM_XE_EXEC_QUEUE_SET_PROPERTY	0x0e
 #define DRM_XE_VM_GET_PROPERTY		0x0f
+#define DRM_XE_VM_RESTART		0x10
 
 /* Must be kept compact -- no holes */
 
@@ -128,6 +130,7 @@ extern "C" {
 #define DRM_IOCTL_XE_VM_QUERY_MEM_RANGE_ATTRS	DRM_IOWR(DRM_COMMAND_BASE + DRM_XE_VM_QUERY_MEM_RANGE_ATTRS, struct drm_xe_vm_query_mem_range_attr)
 #define DRM_IOCTL_XE_EXEC_QUEUE_SET_PROPERTY	DRM_IOW(DRM_COMMAND_BASE + DRM_XE_EXEC_QUEUE_SET_PROPERTY, struct drm_xe_exec_queue_set_property)
 #define DRM_IOCTL_XE_VM_GET_PROPERTY		DRM_IOWR(DRM_COMMAND_BASE + DRM_XE_VM_GET_PROPERTY, struct drm_xe_vm_get_property)
+#define DRM_IOCTL_XE_VM_RESTART			DRM_IOW(DRM_COMMAND_BASE + DRM_XE_VM_RESTART, struct drm_xe_vm_restart)
 
 /**
  * DOC: Xe IOCTL Extensions
@@ -991,6 +994,7 @@ struct drm_xe_vm_create {
 #define DRM_XE_VM_CREATE_FLAG_LR_MODE	        (1 << 1)
 #define DRM_XE_VM_CREATE_FLAG_FAULT_MODE	(1 << 2)
 #define DRM_XE_VM_CREATE_FLAG_NO_VM_OVERCOMMIT  (1 << 3)
+#define DRM_XE_VM_CREATE_FLAG_RESTARTABLE       (1 << 4)
 	/** @flags: Flags */
 	__u32 flags;
 
@@ -2609,6 +2613,42 @@ enum drm_xe_ras_error_component {
 	[DRM_XE_RAS_ERR_COMP_SOC_INTERNAL] = "soc-internal"		\
 }
 
+/**
+ * DOC: DRM_XE_VM_RESTART
+ *
+ * Synchronously restart a VM by running its preempt-rebind worker in the
+ * calling context.  The VM must be in preempt-fence mode (i.e. it must have
+ * been created with exec queues that use preempt fences).
+ *
+ * On return the rebind attempt has completed or a retriable error was
+ * encountered.  Any non-retriable error is surfaced through the event
+ * mechanism if the caller has subscribed to %DRM_XE_EVENT_MASK_VM_ERR.
+ * The IOCTL may return -EAGAIN if userptr memory needs to be repinned;
+ * callers should retry in that case.
+ */
+
+/**
+ * struct drm_xe_vm_restart - restart a VM's preempt-rebind worker
+ *
+ * Used with %DRM_IOCTL_XE_VM_RESTART.
+ */
+struct drm_xe_vm_restart {
+	/** @vm_id: ID of the VM to restart */
+	__u32 vm_id;
+	/** @pad: reserved, must be zero */
+	__u32 pad;
+	/**
+	 * @timestamp_ns: optional CLOCK_MONOTONIC timestamp in nanoseconds.
+	 * When non-zero, the driver logs the delay between this timestamp and
+	 * the point the rebind completes, which can be used to measure the
+	 * response latency from event delivery to VM restart.  Pass zero to
+	 * disable the logging.
+	 */
+	__u64 timestamp_ns;
+	/** @reserved: reserved, must be zero */
+	__u64 reserved;
+};
+
 #if defined(__cplusplus)
 }
 #endif
diff --git a/lib/xe/xe_ioctl.c b/lib/xe/xe_ioctl.c
index c8ed99182..f102fe34e 100644
--- a/lib/xe/xe_ioctl.c
+++ b/lib/xe/xe_ioctl.c
@@ -337,6 +337,50 @@ void xe_vm_get_property(int fd, uint32_t vm, struct drm_xe_vm_get_property *quer
 	igt_assert_eq(igt_ioctl(fd, DRM_IOCTL_XE_VM_GET_PROPERTY, query), 0);
 }
 
+/**
+ * __xe_vm_restart() - restart a VM's preempt-rebind worker (failable)
+ * @fd: open Xe DRM device file descriptor
+ * @vm: VM id to restart
+ * @timestamp_ns: CLOCK_MONOTONIC timestamp from the triggering event, or 0
+ *
+ * Calls %DRM_IOCTL_XE_VM_RESTART, retrying up to 10 times on -EAGAIN as
+ * required when userptr memory needs repinning.
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int __xe_vm_restart(int fd, uint32_t vm, uint64_t timestamp_ns)
+{
+	struct drm_xe_vm_restart restart = {
+		.vm_id = vm,
+		.timestamp_ns = timestamp_ns,
+	};
+	int err, tries = 10;
+
+	do {
+		err = igt_ioctl(fd, DRM_IOCTL_XE_VM_RESTART, &restart);
+		if (err) {
+			err = -errno;
+			igt_assume(err);
+			errno = 0;
+		}
+	} while (err == -EAGAIN && --tries > 0);
+
+	return err;
+}
+
+/**
+ * xe_vm_restart() - restart a VM's preempt-rebind worker
+ * @fd: open Xe DRM device file descriptor
+ * @vm: VM id to restart
+ * @timestamp_ns: CLOCK_MONOTONIC timestamp from the triggering event, or 0
+ *
+ * Calls __xe_vm_restart() and asserts success.
+ */
+void xe_vm_restart(int fd, uint32_t vm, uint64_t timestamp_ns)
+{
+	igt_assert_eq(__xe_vm_restart(fd, vm, timestamp_ns), 0);
+}
+
 void xe_vm_destroy(int fd, uint32_t vm)
 {
 	struct drm_xe_vm_destroy destroy = {
diff --git a/lib/xe/xe_ioctl.h b/lib/xe/xe_ioctl.h
index bf40fb6bd..95f2ec3d8 100644
--- a/lib/xe/xe_ioctl.h
+++ b/lib/xe/xe_ioctl.h
@@ -66,6 +66,8 @@ void xe_vm_unbind_all_async(int fd, uint32_t vm, uint32_t exec_queue,
 			    uint32_t bo, struct drm_xe_sync *sync,
 			    uint32_t num_syncs);
 void xe_vm_get_property(int fd, uint32_t vm, struct drm_xe_vm_get_property *query);
+int __xe_vm_restart(int fd, uint32_t vm, uint64_t timestamp_ns);
+void xe_vm_restart(int fd, uint32_t vm, uint64_t timestamp_ns);
 void xe_vm_destroy(int fd, uint32_t vm);
 uint32_t __xe_bo_create(int fd, uint32_t vm, uint64_t size, uint32_t placement,
 			uint32_t flags, void *ext, uint32_t *handle);
-- 
2.54.0