From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: xen/arm: kernel BUG at /local/home/julien/works/linux/drivers/xen/swiotlb-xen.c:102 Date: Thu, 06 Nov 2014 12:56:36 +0000 Message-ID: <545B7004.5060406@linaro.org> References: <545A5F1F.9030006@linaro.org> <545B68BB.8020205@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Stefano Stabellini Cc: Ian Campbell , xen-devel List-Id: xen-devel@lists.xenproject.org On 06/11/2014 12:42, Stefano Stabellini wrote: > On Thu, 6 Nov 2014, Julien Grall wrote: >> >> 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. > > Yes, it is safe, but we do need to change those call sites to pass > dev_addr instead, like I have done with unmap_single in the patch I > appended in the last email: Ok. I will give a look to modify all the call site. Regards, > 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 > @@ -449,7 +447,7 @@ static void xen_unmap_single(struct device *hwdev, dma_addr_t dev_addr, > > BUG_ON(dir == DMA_NONE); > > - xen_dma_unmap_page(hwdev, paddr, size, dir, attrs); > + xen_dma_unmap_page(hwdev, dev_addr, size, dir, attrs); > > /* NOTE: We use dev_addr here, not paddr! */ > if (is_xen_swiotlb_buffer(dev_addr)) { > -- Julien Grall