xen/swiotlb: fix allocated size

The allocated size in xen_swiotlb_alloc_coherent() and
xen_swiotlb_free_coherent() is calculated wrong for the case of
XEN_PAGE_SIZE not matching PAGE_SIZE. Fix that.

Fixes: 7250f422 ("xen-swiotlb: use actually allocated size on check physical continuous")
Reported-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Juergen Gross <jgross@suse.com>

drivers/xen/swiotlb-xen.c

@@ -147,7 +147,7 @@ xen_swiotlb_alloc_coherent(struct device *dev, size_t size,
 	void *ret;
 
 	/* Align the allocation to the Xen page size */
-	size = 1UL << (order + XEN_PAGE_SHIFT);
+	size = ALIGN(size, XEN_PAGE_SIZE);
 
 	ret = (void *)__get_free_pages(flags, get_order(size));
 	if (!ret)
@@ -179,7 +179,7 @@ xen_swiotlb_free_coherent(struct device *dev, size_t size, void *vaddr,
 	int order = get_order(size);
 
 	/* Convert the size to actually allocated. */
-	size = 1UL << (order + XEN_PAGE_SHIFT);
+	size = ALIGN(size, XEN_PAGE_SIZE);
 
 	if (WARN_ON_ONCE(dma_handle + size - 1 > dev->coherent_dma_mask) ||
 	    WARN_ON_ONCE(range_straddles_page_boundary(phys, size)))