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Re: [Xen-devel] xen/arm: kernel BUG at /local/home/julien/works/linux/drivers/xen/swiotlb-xen.c:102





On 06/11/2014 11:46, Stefano Stabellini wrote:
Hello Julien,

Hi Stefano,

I didn't manage to reproduce the issue you are seeing but I think you
are right: non-LPAE kernels could get in trouble by calling
xen_bus_to_phys. This problem is not ARM specific per se, but it doesn't
occur on x86 because config XEN depends on X86_32 && X86_PAE.

The following patch should fix the issue:


diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index ac5d41b..489620d 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -96,8 +96,6 @@ static inline phys_addr_t xen_bus_to_phys(dma_addr_t baddr)
        dma_addr_t dma = (dma_addr_t)pfn << PAGE_SHIFT;
        phys_addr_t paddr = dma;

-       BUG_ON(paddr != dma); /* truncation has occurred, should never happen */
-

Are you sure that removing this BUG_ON is safe? There is some of place where we pass a physical address rather than a DMA. See xen_swiotlb_sync_single.

Regards,

--
Julien Grall

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