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Re: [PATCH 01/10] swiotlb-xen: use vmalloc_to_page on vmalloc virt addresses


On 21/05/2020 00:45, Stefano Stabellini wrote:
From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

Don't just assume that virt_to_page works on all virtual addresses.
Instead add a is_vmalloc_addr check and use vmalloc_to_page on vmalloc
virt addresses.

Can you provide an example where swiotlb is used with vmalloc()?

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
  drivers/xen/swiotlb-xen.c | 5 ++++-
  1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index b6d27762c6f8..a42129cba36e 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -335,6 +335,7 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t 
size, void *vaddr,
        int order = get_order(size);
        phys_addr_t phys;
        u64 dma_mask = DMA_BIT_MASK(32);
+       struct page *pg;
if (hwdev && hwdev->coherent_dma_mask)
                dma_mask = hwdev->coherent_dma_mask;
@@ -346,9 +347,11 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t 
size, void *vaddr,
        /* Convert the size to actually allocated. */
        size = 1UL << (order + XEN_PAGE_SHIFT);
+ pg = is_vmalloc_addr(vaddr) ? vmalloc_to_page(vaddr) :
+                                     virt_to_page(vaddr);

Common DMA code seems to protect this check with CONFIG_DMA_REMAP. Is it something we want to do it here as well? Or is there any other condition where vmalloc can happen?

        if (!WARN_ON((dev_addr + size - 1 > dma_mask) ||
                     range_straddles_page_boundary(phys, size)) &&
-           TestClearPageXenRemapped(virt_to_page(vaddr)))
+           TestClearPageXenRemapped(pg))
                xen_destroy_contiguous_region(phys, order);
xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs);


Julien Grall



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