From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH V2 1/3] scsi: mptxsas: try 64 bit DMA when 32 bit DMA fails Date: Tue, 10 Nov 2015 20:13:30 +0100 Message-ID: <6333643.g8NiezT8gD@wuerfel> References: <1447034266-28003-1-git-send-email-okaya@codeaurora.org> <4982446.ZlJVrezq1Y@wuerfel> <564222CB.3000701@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <564222CB.3000701@codeaurora.org> Sender: linux-kernel-owner@vger.kernel.org To: Timur Tabi Cc: Sinan Kaya , linux-arm-kernel@lists.infradead.org, Abhijit Mahajan , Nagalakshmi Nandigama , linux-scsi@vger.kernel.org, jcm@redhat.com, "James E.J. Bottomley" , linux-kernel@vger.kernel.org, Sreekanth Reddy , Praveen Krishnamoorthy , cov@codeaurora.org, linux-arm-msm@vger.kernel.org, agross@codeaurora.org, MPT-FusionLinux.pdl@avagotech.com, Hannes Reinecke List-Id: linux-scsi@vger.kernel.org On Tuesday 10 November 2015 11:00:59 Timur Tabi wrote: > On 11/10/2015 10:47 AM, Arnd Bergmann wrote: > > What BenH was worried about here is that the driver sets different masks > > for streaming and coherent mappings, which is indeed a worry that > > could hit us on ARM as well, but I suppose we'll have to deal with > > that in platform code. > > > > Setting both masks to 32-bit is something that a lot of drivers do, > > and without IOMMU enabled, you'd hit the same bug on all of them. > > Also note that I think that on PowerPC, the mask is set to 32 by default > for all devices. I don't think we do that on ARM64. So on PowerPC, > some drivers get away with not explicitly setting the mask. > If the mask is 64-bit by default on ARM64, that is a bug that we need to fix urgently. Can you verify this? A lot of PCI devices can only do 32-bit DMA, and we have plenty of drivers that don't bother setting a mask at all because the 32-bit mask is the default on all other architectures. Arnd