Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933216AbbHJLZZ (ORCPT ); Mon, 10 Aug 2015 07:25:25 -0400 Received: from smtp.citrix.com ([66.165.176.89]:30679 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753932AbbHJLZR (ORCPT ); Mon, 10 Aug 2015 07:25:17 -0400 X-IronPort-AV: E=Sophos;i="5.15,645,1432598400"; d="scan'208";a="289607886" Message-ID: <55C889E4.8050307@citrix.com> Date: Mon, 10 Aug 2015 12:24:20 +0100 From: Julien Grall User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.8.0 MIME-Version: 1.0 To: Stefano Stabellini CC: , , David Vrabel , , Boris Ostrovsky , Subject: Re: [Xen-devel] [PATCH v3 09/20] xen/biomerge: Don't allow biovec to be merge when Linux is not using 4KB page References: <1438966019-19322-1-git-send-email-julien.grall@citrix.com> <1438966019-19322-10-git-send-email-julien.grall@citrix.com> In-Reply-To: Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1278 Lines: 36 Hi Stefano, On 10/08/15 11:50, Stefano Stabellini wrote: > On Fri, 7 Aug 2015, Julien Grall wrote: >> On ARM all dma-capable devices on a same platform may not be protected >> by an IOMMU. The DMA requests have to use the BFN (i.e MFN on ARM) in >> order to use correctly the device. >> >> While the DOM0 memory is allocated in a 1:1 fashion (PFN == MFN), grant >> mapping will screw this contiguous mapping. >> >> When Linux is using 64KB page granularitary, the page may be split >> accross multiple non-contiguous MFN (Xen is using 4KB page >> granularity). Therefore a DMA request will likely fail. >> >> Checking that a 64KB page is using contiguous MFN is tedious. For >> now, always says that biovec are not mergeable. >> >> Signed-off-by: Julien Grall > > Please fix the grammar in the subject line. If I made a mistake it's unlikely that I will find myself which one I made. Anyway, I guess you mean to replace merge by merged? I don't see any other in the subject. Regards, -- Julien Grall -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/