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[PATCH for v4.9 LTS 34/86] swiotlb-xen: update dev_addr after swapping pages




From: Stefano Stabellini <sstabellini@xxxxxxxxxx>

[ Upstream commit f1225ee4c8fcf09afaa199b8b1f0450f38b8cd11 ]

In xen_swiotlb_map_page and xen_swiotlb_map_sg_attrs, if the original
page is not suitable, we swap it for another page from the swiotlb
pool.

In these cases, we don't update the previously calculated dma address
for the page before calling xen_dma_map_page. Thus, we end up calling
xen_dma_map_page passing the wrong dev_addr, resulting in
xen_dma_map_page mistakenly assuming that the page is foreign when it is
local.

Fix the bug by updating dev_addr appropriately.

This change has no effect on x86, because xen_dma_map_page is a stub
there.

Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Signed-off-by: Pooya Keshavarzi <Pooya.Keshavarzi@xxxxxxxxxxxx>
Tested-by: Pooya Keshavarzi <Pooya.Keshavarzi@xxxxxxxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
---
 drivers/xen/swiotlb-xen.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 8e7a3d646531..679f79f68182 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -409,9 +409,9 @@ dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
 	if (map == SWIOTLB_MAP_ERROR)
 		return DMA_ERROR_CODE;
 
+	dev_addr = xen_phys_to_bus(map);
 	xen_dma_map_page(dev, pfn_to_page(map >> PAGE_SHIFT),
 					dev_addr, map & ~PAGE_MASK, size, dir, attrs);
-	dev_addr = xen_phys_to_bus(map);
 
 	/*
 	 * Ensure that the address returned is DMA'ble
@@ -567,13 +567,14 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
 				sg_dma_len(sgl) = 0;
 				return 0;
 			}
+			dev_addr = xen_phys_to_bus(map);
 			xen_dma_map_page(hwdev, pfn_to_page(map >> PAGE_SHIFT),
 						dev_addr,
 						map & ~PAGE_MASK,
 						sg->length,
 						dir,
 						attrs);
-			sg->dma_address = xen_phys_to_bus(map);
+			sg->dma_address = dev_addr;
 		} else {
 			/* we are not interested in the dma_addr returned by
 			 * xen_dma_map_page, only in the potential cache flushes executed
-- 
2.11.0