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Subject[PATCH] swiotlb-xen: override common mmap and get_sgtable dma ops
Date
This commit is dedicated to fix incorrect convertion from
cpu_addr to page address in cases when we get virtual
address which allocated throught xen_swiotlb_alloc_coherent()
and can be mapped in the vmalloc range.
As the result, virt_to_page() cannot convert this address
properly and return incorrect page address.

Need to detect such cases and obtains the page address using
vmalloc_to_page() instead.

The reference code was copied from kernel/dma/ops_helpers.c
and modified to provide additional detections as described
above.

Signed-off-by: Roman Skakun <roman_skakun@epam.com>
Reviewed-by: Andrii Anisov <andrii_anisov@epam.com>

---
Also, I have observed that the original common code didn't
make additional checks about contiguity of the memory region
represented by cpu_addr and size

May be, this means that these functions can get only physically
contiguous memory.
Is this correct?

Cheers!

---
drivers/xen/swiotlb-xen.c | 51 +++++++++++++++++++++++++++++++++++++--
1 file changed, 49 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 2b385c1b4a99..f99c98472927 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -563,6 +563,53 @@ xen_swiotlb_dma_supported(struct device *hwdev, u64 mask)
return xen_virt_to_bus(hwdev, xen_io_tlb_end - 1) <= mask;
}

+static int
+xen_swiotlb_dma_mmap(struct device *dev, struct vm_area_struct *vma,
+ void *cpu_addr, dma_addr_t dma_addr, size_t size,
+ unsigned long attrs)
+{
+ unsigned long user_count = vma_pages(vma);
+ unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+ unsigned long off = vma->vm_pgoff;
+ struct page *page;
+
+ if (is_vmalloc_addr(cpu_addr))
+ page = vmalloc_to_page(cpu_addr);
+ else
+ page = virt_to_page(cpu_addr);
+
+ vma->vm_page_prot = dma_pgprot(dev, vma->vm_page_prot, attrs);
+
+ if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret))
+ return -ENXIO;
+
+ if (off >= count || user_count > count - off)
+ return -ENXIO;
+
+ return remap_pfn_range(vma, vma->vm_start,
+ page_to_pfn(page) + vma->vm_pgoff,
+ user_count << PAGE_SHIFT, vma->vm_page_prot);
+}
+
+static int
+xen_swiotlb_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
+ void *cpu_addr, dma_addr_t dma_addr, size_t size,
+ unsigned long attrs)
+{
+ struct page *page;
+ int ret;
+
+ if (is_vmalloc_addr(cpu_addr))
+ page = vmalloc_to_page(cpu_addr);
+ else
+ page = virt_to_page(cpu_addr);
+
+ ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
+ if (!ret)
+ sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
+ return ret;
+}
+
const struct dma_map_ops xen_swiotlb_dma_ops = {
.alloc = xen_swiotlb_alloc_coherent,
.free = xen_swiotlb_free_coherent,
@@ -575,8 +622,8 @@ const struct dma_map_ops xen_swiotlb_dma_ops = {
.map_page = xen_swiotlb_map_page,
.unmap_page = xen_swiotlb_unmap_page,
.dma_supported = xen_swiotlb_dma_supported,
- .mmap = dma_common_mmap,
- .get_sgtable = dma_common_get_sgtable,
+ .mmap = xen_swiotlb_dma_mmap,
+ .get_sgtable = xen_swiotlb_dma_get_sgtable,
.alloc_pages = dma_common_alloc_pages,
.free_pages = dma_common_free_pages,
};
--
2.27.0
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