Re: [PATCH v9 13/13] swiotlb-xen: remove BUG_ON in xen_bus_to_phys

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, Nov 12, 2014 at 11:40:54AM +0000, Stefano Stabellini wrote:
> On x86 truncation cannot occur because config XEN depends on X86_64 ||
> (X86_32 && X86_PAE).
> 
> On ARM truncation can occur without CONFIG_ARM_LPAE, when the dma
> operation involves foreign grants. However in that case the physical
> address returned by xen_bus_to_phys is actually invalid (there is no mfn
> to pfn tracking for foreign grants on ARM) and it is not used.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
>  drivers/xen/swiotlb-xen.c |    2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index 498b654..153cf14 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 */
> -
>  	paddr |= baddr & ~PAGE_MASK;
>  
>  	return paddr;
> -- 
> 1.7.10.4
>