drm/xe/uapi: Use LR abbrev for long-running vms

Currently we're using "compute mode" for long running VMs using
preempt-fences for memory management, and "fault mode" for long
running VMs using page faults.

Change this to use the terminology "long-running" abbreviated as LR for
long-running VMs. These VMs can then either be in preempt-fence mode or
fault mode. The user can force fault mode at creation time, but otherwise
the driver can choose to use fault- or preempt-fence mode for long-running
vms depending on the device capabilities. Initially unless fault-mode is
specified, the driver uses preempt-fence mode.

v2:
- Fix commit message wording and the documentation around
  CREATE_FLAG_LR_MODE and CREATE_FLAG_FAULT_MODE

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Francois Dugast <francois.dugast@intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_vm.c

@@ -1921,7 +1921,7 @@ static int xe_vm_unbind(struct xe_vm *vm, struct xe_vma *vma,
 }
 
 #define ALL_DRM_XE_VM_CREATE_FLAGS (DRM_XE_VM_CREATE_FLAG_SCRATCH_PAGE | \
-				    DRM_XE_VM_CREATE_FLAG_COMPUTE_MODE | \
+				    DRM_XE_VM_CREATE_FLAG_LR_MODE | \
 				    DRM_XE_VM_CREATE_FLAG_ASYNC_DEFAULT | \
 				    DRM_XE_VM_CREATE_FLAG_FAULT_MODE)
 
@@ -1957,7 +1957,7 @@ int xe_vm_create_ioctl(struct drm_device *dev, void *data,
 			 args->flags & DRM_XE_VM_CREATE_FLAG_FAULT_MODE))
 		return -EINVAL;
 
-	if (XE_IOCTL_DBG(xe, args->flags & DRM_XE_VM_CREATE_FLAG_COMPUTE_MODE &&
+	if (XE_IOCTL_DBG(xe, !(args->flags & DRM_XE_VM_CREATE_FLAG_LR_MODE) &&
 			 args->flags & DRM_XE_VM_CREATE_FLAG_FAULT_MODE))
 		return -EINVAL;
 
@@ -1974,12 +1974,12 @@ int xe_vm_create_ioctl(struct drm_device *dev, void *data,
 
 	if (args->flags & DRM_XE_VM_CREATE_FLAG_SCRATCH_PAGE)
 		flags |= XE_VM_FLAG_SCRATCH_PAGE;
-	if (args->flags & DRM_XE_VM_CREATE_FLAG_COMPUTE_MODE)
+	if (args->flags & DRM_XE_VM_CREATE_FLAG_LR_MODE)
 		flags |= XE_VM_FLAG_LR_MODE;
 	if (args->flags & DRM_XE_VM_CREATE_FLAG_ASYNC_DEFAULT)
 		flags |= XE_VM_FLAG_ASYNC_DEFAULT;
 	if (args->flags & DRM_XE_VM_CREATE_FLAG_FAULT_MODE)
-		flags |= XE_VM_FLAG_LR_MODE | XE_VM_FLAG_FAULT_MODE;
+		flags |= XE_VM_FLAG_FAULT_MODE;
 
 	vm = xe_vm_create(xe, flags);
 	if (IS_ERR(vm))

include/uapi/drm/xe_drm.h

@@ -648,8 +648,29 @@ struct drm_xe_vm_create {
 	__u64 extensions;
 
 #define DRM_XE_VM_CREATE_FLAG_SCRATCH_PAGE	(1 << 0)
-#define DRM_XE_VM_CREATE_FLAG_COMPUTE_MODE	(1 << 1)
+	/*
+	 * An LR, or Long Running VM accepts exec submissions
+	 * to its exec_queues that don't have an upper time limit on
+	 * the job execution time. But exec submissions to these
+	 * don't allow any of the flags DRM_XE_SYNC_FLAG_SYNCOBJ,
+	 * DRM_XE_SYNC_FLAG_TIMELINE_SYNCOBJ, DRM_XE_SYNC_FLAG_DMA_BUF,
+	 * used as out-syncobjs, that is, together with DRM_XE_SYNC_FLAG_SIGNAL.
+	 * LR VMs can be created in recoverable page-fault mode using
+	 * DRM_XE_VM_CREATE_FLAG_FAULT_MODE, if the device supports it.
+	 * If that flag is omitted, the UMD can not rely on the slightly
+	 * different per-VM overcommit semantics that are enabled by
+	 * DRM_XE_VM_CREATE_FLAG_FAULT_MODE (see below), but KMD may
+	 * still enable recoverable pagefaults if supported by the device.
+	 */
+#define DRM_XE_VM_CREATE_FLAG_LR_MODE	        (1 << 1)
 #define DRM_XE_VM_CREATE_FLAG_ASYNC_DEFAULT	(1 << 2)
+	/*
+	 * DRM_XE_VM_CREATE_FLAG_FAULT_MODE requires also
+	 * DRM_XE_VM_CREATE_FLAG_LR_MODE. It allows memory to be allocated
+	 * on demand when accessed, and also allows per-VM overcommit of memory.
+	 * The xe driver internally uses recoverable pagefaults to implement
+	 * this.
+	 */
 #define DRM_XE_VM_CREATE_FLAG_FAULT_MODE	(1 << 3)
 	/** @flags: Flags */
 	__u32 flags;