[PATCH, RFC] swiotlb-xen: fix dma to physical address translation for cache operations

[Christoph Hellwig <hch@xxxxxx>]

All other places in swiotlb-xen got from PFN to BFN and then call
phys_to_dma on the result or vice versa, but the reverse mapping used
for cache maintenance skips the BFN to PFN mapping.

[Note: only found by code inspection, please review very carefully!]

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 drivers/xen/swiotlb-xen.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 67aa74d201627d..e4620303138b4d 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -234,7 +234,7 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, 
struct page *page,
 
 done:
        if (!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
-               if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dev_addr))))
+               if (pfn_valid(PFN_DOWN(phys)))
                        arch_sync_dma_for_device(phys, size, dir);
                else
                        xen_dma_sync_for_device(dev, dev_addr, size, dir);
@@ -258,7 +258,7 @@ static void xen_swiotlb_unmap_page(struct device *hwdev, 
dma_addr_t dev_addr,
        BUG_ON(dir == DMA_NONE);
 
        if (!dev_is_dma_coherent(hwdev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
-               if (pfn_valid(PFN_DOWN(dma_to_phys(hwdev, dev_addr))))
+               if (pfn_valid(PFN_DOWN(paddr)))
                        arch_sync_dma_for_cpu(paddr, size, dir);
                else
                        xen_dma_sync_for_cpu(hwdev, dev_addr, size, dir);
@@ -276,7 +276,7 @@ xen_swiotlb_sync_single_for_cpu(struct device *dev, 
dma_addr_t dma_addr,
        phys_addr_t paddr = xen_dma_to_phys(dev, dma_addr);
 
        if (!dev_is_dma_coherent(dev)) {
-               if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr))))
+               if (pfn_valid(PFN_DOWN(paddr)))
                        arch_sync_dma_for_cpu(paddr, size, dir);
                else
                        xen_dma_sync_for_cpu(dev, dma_addr, size, dir);
@@ -296,7 +296,7 @@ xen_swiotlb_sync_single_for_device(struct device *dev, 
dma_addr_t dma_addr,
                swiotlb_sync_single_for_device(dev, paddr, size, dir);
 
        if (!dev_is_dma_coherent(dev)) {
-               if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr))))
+               if (pfn_valid(PFN_DOWN(paddr)))
                        arch_sync_dma_for_device(paddr, size, dir);
                else
                        xen_dma_sync_for_device(dev, dma_addr, size, dir);
-- 
2.39.2