[Xen-devel] [xev-devel][PATCH][linux-4.19] swiotlb-xen.c: Fixed cache invalidation fault

[Nataliya Korovkina <malus.brandywine@xxxxxxxxx>]

Problem: xen_swiotlb_map_sg_attrs() maps a set of buffers described in 
scatterlist.
It calls xen_dma_map_page() and sets sglist.dma_address to the address 
calculated by
xen_phys_to_bus(). Let's call it dma_address_1.

xen_dma_map_page() maps the area and gets dma address different from 
dma_address_1,
let's call it dma_address_2. Then function __swiotlb_map_page() makes 
conversion:
dma_addr -> phys_addr -> virt_addr   using dma_address_2 and passes "virt_addr"
to __dma_map_area(), the latter successfully invalidates cache.

When xen_swiotlb_unmap_sg_attrs() unmaps the area it passes dma_address_1
to __swiotlb_unmap_page().   __swiotlb_unmap_page() makes the same convertion:
dma_addr -> phys_addr -> virt_addr using dma_address_1 and passes "virt_addr"
to __dma_map_area(), the latter gets Data Abort in attempt to invalidate cache.

The problem manfests on devices that have dma_pfn_offset != 0.
Specifically, while loading brcmfmac module (BCM4345 WiFi chip) in Dom0.

What was done: sglist.dma_address is set to phys_to_dma("phys").

Signed-off-by: Nataliya Korovkina <malus.brandywine@xxxxxxxxx>
---
 drivers/xen/swiotlb-xen.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index a6f9ba85dc4b..9363a52e4756 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -583,7 +583,7 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct 
scatterlist *sgl,
                                                sg->length,
                                                dir,
                                                attrs);
-                       sg->dma_address = dev_addr;
+                       sg->dma_address = phys_to_dma(hwdev, dev_addr);
                } else {
                        /* we are not interested in the dma_addr returned by
                         * xen_dma_map_page, only in the potential cache 
flushes executed
@@ -594,7 +594,7 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct 
scatterlist *sgl,
                                                sg->length,
                                                dir,
                                                attrs);
-                       sg->dma_address = dev_addr;
+                       sg->dma_address = phys_to_dma(hwdev, dev_addr);
                }
                sg_dma_len(sg) = sg->length;
        }
-- 
2.17.1


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