xen/swiotlb: add alignment check for dma buffers

When checking a memory buffer to be consecutive in machine memory,
the alignment needs to be checked, too. Failing to do so might result
in DMA memory not being aligned according to its requested size,
leading to error messages like:

  4xxx 0000:2b:00.0: enabling device (0140 -> 0142)
  4xxx 0000:2b:00.0: Ring address not aligned
  4xxx 0000:2b:00.0: Failed to initialise service qat_crypto
  4xxx 0000:2b:00.0: Resetting device qat_dev0
  4xxx: probe of 0000:2b:00.0 failed with error -14

Fixes: 9435cce8 ("xen/swiotlb: Add support for 64KB page granularity")
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Juergen Gross <jgross@suse.com>

drivers/xen/swiotlb-xen.c

@@ -78,9 +78,15 @@ static inline int range_straddles_page_boundary(phys_addr_t p, size_t size)
 {
 	unsigned long next_bfn, xen_pfn = XEN_PFN_DOWN(p);
 	unsigned int i, nr_pages = XEN_PFN_UP(xen_offset_in_page(p) + size);
+	phys_addr_t algn = 1ULL << (get_order(size) + PAGE_SHIFT);
 
 	next_bfn = pfn_to_bfn(xen_pfn);
 
+	/* If buffer is physically aligned, ensure DMA alignment. */
+	if (IS_ALIGNED(p, algn) &&
+	    !IS_ALIGNED((phys_addr_t)next_bfn << XEN_PAGE_SHIFT, algn))
+		return 1;
+
 	for (i = 1; i < nr_pages; i++)
 		if (pfn_to_bfn(++xen_pfn) != ++next_bfn)
 			return 1;