drm/xe: Convert to USM lock to rwsem

Remove contention from GPU fault path for ASID->VM lookup.
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240918054436.1971839-1-matthew.brost@intel.com
(cherry picked from commit 1378c633a3fbfeb344c486ffda0e920a21e62712)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

drivers/gpu/drm/xe/xe_device.c

@@ -339,9 +339,7 @@ struct xe_device *xe_device_create(struct pci_dev *pdev,
 
 	init_waitqueue_head(&xe->ufence_wq);
 
-	err = drmm_mutex_init(&xe->drm, &xe->usm.lock);
-	if (err)
-		goto err;
+	init_rwsem(&xe->usm.lock);
 
 	xa_init_flags(&xe->usm.asid_to_vm, XA_FLAGS_ALLOC);
 

drivers/gpu/drm/xe/xe_device_types.h

@@ -369,7 +369,7 @@ struct xe_device {
 		/** @usm.next_asid: next ASID, used to cyclical alloc asids */
 		u32 next_asid;
 		/** @usm.lock: protects UM state */
-		struct mutex lock;
+		struct rw_semaphore lock;
 	} usm;
 
 	/** @pinned: pinned BO state */

drivers/gpu/drm/xe/xe_gt_pagefault.c

@@ -198,13 +198,13 @@ static int handle_pagefault(struct xe_gt *gt, struct pagefault *pf)
 		return -EFAULT;
 
 	/* ASID to VM */
-	mutex_lock(&xe->usm.lock);
+	down_read(&xe->usm.lock);
 	vm = xa_load(&xe->usm.asid_to_vm, pf->asid);
 	if (vm && xe_vm_in_fault_mode(vm))
 		xe_vm_get(vm);
 	else
 		vm = NULL;
-	mutex_unlock(&xe->usm.lock);
+	up_read(&xe->usm.lock);
 	if (!vm)
 		return -EINVAL;
 
@@ -549,11 +549,11 @@ static int handle_acc(struct xe_gt *gt, struct acc *acc)
 		return -EINVAL;
 
 	/* ASID to VM */
-	mutex_lock(&xe->usm.lock);
+	down_read(&xe->usm.lock);
 	vm = xa_load(&xe->usm.asid_to_vm, acc->asid);
 	if (vm)
 		xe_vm_get(vm);
-	mutex_unlock(&xe->usm.lock);
+	up_read(&xe->usm.lock);
 	if (!vm || !xe_vm_in_fault_mode(vm))
 		return -EINVAL;
 

drivers/gpu/drm/xe/xe_vm.c

@@ -1613,7 +1613,7 @@ void xe_vm_close_and_put(struct xe_vm *vm)
 
 	up_write(&vm->lock);
 
-	mutex_lock(&xe->usm.lock);
+	down_write(&xe->usm.lock);
 	if (vm->usm.asid) {
 		void *lookup;
 
@@ -1623,7 +1623,7 @@ void xe_vm_close_and_put(struct xe_vm *vm)
 		lookup = xa_erase(&xe->usm.asid_to_vm, vm->usm.asid);
 		xe_assert(xe, lookup == vm);
 	}
-	mutex_unlock(&xe->usm.lock);
+	up_write(&xe->usm.lock);
 
 	for_each_tile(tile, xe, id)
 		xe_range_fence_tree_fini(&vm->rftree[id]);
@@ -1772,11 +1772,11 @@ int xe_vm_create_ioctl(struct drm_device *dev, void *data,
 		goto err_close_and_put;
 
 	if (xe->info.has_asid) {
-		mutex_lock(&xe->usm.lock);
+		down_write(&xe->usm.lock);
 		err = xa_alloc_cyclic(&xe->usm.asid_to_vm, &asid, vm,
 				      XA_LIMIT(1, XE_MAX_ASID - 1),
 				      &xe->usm.next_asid, GFP_KERNEL);
-		mutex_unlock(&xe->usm.lock);
+		up_write(&xe->usm.lock);
 		if (err < 0)
 			goto err_free_id;