swiotlb-xen: limit init retries

Due to the use of max(1024, ...) there's no point retrying (and issuing
bogus log messages) when the number of slabs is already no larger than
this minimum value.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

Link: https://lore.kernel.org/r/984fa426-2b7b-4b77-5ce8-766619575b7f@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>

Author: jbeulich

drivers/xen/swiotlb-xen.c

@@ -207,7 +207,7 @@ int __ref xen_swiotlb_init(void)
 	swiotlb_set_max_segment(PAGE_SIZE);
 	return 0;
 error:
-	if (repeat--) {
+	if (nslabs > 1024 && repeat--) {
 		/* Min is 2MB */
 		nslabs = max(1024UL, ALIGN(nslabs >> 1, IO_TLB_SEGSIZE));
 		bytes = nslabs << IO_TLB_SHIFT;
@@ -243,7 +243,7 @@ void __init xen_swiotlb_init_early(void)
 	rc = xen_swiotlb_fixup(start, nslabs);
 	if (rc) {
 		memblock_free(__pa(start), PAGE_ALIGN(bytes));
-		if (repeat--) {
+		if (nslabs > 1024 && repeat--) {
 			/* Min is 2MB */
 			nslabs = max(1024UL, ALIGN(nslabs >> 1, IO_TLB_SEGSIZE));
 			bytes = nslabs << IO_TLB_SHIFT;