xen-swiotlb: use io_tlb_end in xen_swiotlb_dma_supported

Use the existing variable that holds the physical address for
xen_io_tlb_end to simplify xen_swiotlb_dma_supported a bit, and remove
the otherwise unused xen_io_tlb_end variable and the xen_virt_to_bus
helper.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/swiotlb-xen.c

@@ -46,7 +46,7 @@
  * API.
  */
 
-static char *xen_io_tlb_start, *xen_io_tlb_end;
+static char *xen_io_tlb_start;
 static unsigned long xen_io_tlb_nslabs;
 /*
  * Quick lookup value of the bus address of the IOTLB.
@@ -82,11 +82,6 @@ static inline phys_addr_t xen_dma_to_phys(struct device *dev,
 	return xen_bus_to_phys(dev, dma_to_phys(dev, dma_addr));
 }
 
-static inline dma_addr_t xen_virt_to_bus(struct device *dev, void *address)
-{
-	return xen_phys_to_dma(dev, virt_to_phys(address));
-}
-
 static inline int range_straddles_page_boundary(phys_addr_t p, size_t size)
 {
 	unsigned long next_bfn, xen_pfn = XEN_PFN_DOWN(p);
@@ -250,7 +245,6 @@ int __ref xen_swiotlb_init(int verbose, bool early)
 		rc = swiotlb_late_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs);
 
 end:
-	xen_io_tlb_end = xen_io_tlb_start + bytes;
 	if (!rc)
 		swiotlb_set_max_segment(PAGE_SIZE);
 
@@ -558,7 +552,7 @@ xen_swiotlb_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
 static int
 xen_swiotlb_dma_supported(struct device *hwdev, u64 mask)
 {
-	return xen_virt_to_bus(hwdev, xen_io_tlb_end - 1) <= mask;
+	return xen_phys_to_dma(hwdev, io_tlb_end - 1) <= mask;
 }
 
 const struct dma_map_ops xen_swiotlb_dma_ops = {