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[50.57.142.19]) by mx.google.com with ESMTPS id e2si4804936vcf.81.2014.11.06.04.51.31 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Thu, 06 Nov 2014 04:51:31 -0800 (PST) Received-SPF: none (google.com: xen-devel-bounces@lists.xen.org does not designate permitted sender hosts) client-ip=50.57.142.19; Received: from localhost ([127.0.0.1] helo=lists.xen.org) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1XmMVe-0006aa-0t; Thu, 06 Nov 2014 12:49:54 +0000 Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1XmMVc-0006aQ-EB for xen-devel@lists.xen.org; Thu, 06 Nov 2014 12:49:52 +0000 Received: from [85.158.137.68] by server-14.bemta-3.messagelabs.com id E7/98-07724-F6E6B545; Thu, 06 Nov 2014 12:49:51 +0000 X-Env-Sender: Stefano.Stabellini@citrix.com X-Msg-Ref: server-5.tower-31.messagelabs.com!1415278189!10889583!1 X-Originating-IP: [66.165.176.89] X-SpamReason: No, hits=0.0 required=7.0 tests=sa_preprocessor: VHJ1c3RlZCBJUDogNjYuMTY1LjE3Ni44OSA9PiAyMDMwMDc=\n X-StarScan-Received: X-StarScan-Version: 6.12.4; banners=-,-,- X-VirusChecked: Checked Received: (qmail 7774 invoked from network); 6 Nov 2014 12:49:51 -0000 Received: from smtp.citrix.com (HELO SMTP.CITRIX.COM) (66.165.176.89) by server-5.tower-31.messagelabs.com with RC4-SHA encrypted SMTP; 6 Nov 2014 12:49:51 -0000 X-IronPort-AV: E=Sophos;i="5.07,325,1413244800"; d="scan'208";a="188739920" Received: from ukmail1.uk.xensource.com (10.80.16.128) by smtprelay.citrix.com (10.13.107.79) with Microsoft SMTP Server id 14.3.181.6; Thu, 6 Nov 2014 07:49:49 -0500 Received: from kaball.uk.xensource.com ([10.80.2.59]) by ukmail1.uk.xensource.com with esmtp (Exim 4.69) (envelope-from ) id 1XmMP5-0006Yd-GB; Thu, 06 Nov 2014 12:43:07 +0000 Date: Thu, 6 Nov 2014 12:42:59 +0000 From: Stefano Stabellini X-X-Sender: sstabellini@kaball.uk.xensource.com To: Julien Grall In-Reply-To: <545B68BB.8020205@linaro.org> Message-ID: References: <545A5F1F.9030006@linaro.org> <545B68BB.8020205@linaro.org> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 X-DLP: MIA1 Cc: xen-devel , Ian Campbell , Stefano Stabellini Subject: Re: [Xen-devel] xen/arm: kernel BUG at /local/home/julien/works/linux/drivers/xen/swiotlb-xen.c:102 X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: List-Unsubscribe: , List-Post: , List-Help: , List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org X-Removed-Original-Auth: Dkim didn't pass. X-Original-Sender: stefano.stabellini@eu.citrix.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of patch+caf_=patchwork-forward=linaro.org@linaro.org designates 209.85.217.169 as permitted sender) smtp.mail=patch+caf_=patchwork-forward=linaro.org@linaro.org Mailing-list: list patchwork-forward@linaro.org; contact patchwork-forward+owners@linaro.org X-Google-Group-Id: 836684582541 List-Archive: 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: 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)) {