drm/xe: Do not run GPU page fault handler on a closed VM

Closing a VM removes page table memory thus we shouldn't touch page
tables when a VM is closed. Do not run the GPU page fault handler once
the VM is closed to avoid touching page tables.
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240911011820.825127-1-matthew.brost@intel.com
(cherry picked from commit f96dbf7c321d70834d46f3aedb75a671e839b51e)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

drivers/gpu/drm/xe/xe_gt_pagefault.c

@@ -212,6 +212,12 @@ static int handle_pagefault(struct xe_gt *gt, struct pagefault *pf)
 	 * TODO: Change to read lock? Using write lock for simplicity.
 	 */
 	down_write(&vm->lock);
+
+	if (xe_vm_is_closed(vm)) {
+		err = -ENOENT;
+		goto unlock_vm;
+	}
+
 	vma = lookup_vma(vm, pf->page_addr);
 	if (!vma) {
 		err = -EINVAL;