Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753386AbaDDPCK (ORCPT ); Fri, 4 Apr 2014 11:02:10 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:52222 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752818AbaDDPCG (ORCPT ); Fri, 4 Apr 2014 11:02:06 -0400 X-IronPort-AV: E=Sophos;i="4.97,795,1389744000"; d="scan'208";a="116829393" Message-ID: <533EC966.7030101@citrix.com> Date: Fri, 4 Apr 2014 16:01:58 +0100 From: David Vrabel User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.16) Gecko/20121215 Iceowl/1.0b1 Icedove/3.0.11 MIME-Version: 1.0 To: Roger Pau Monne CC: , , Konrad Rzeszutek Wilk , Boris Ostrovsky Subject: Re: [PATCH] xen-blkback: only attach blkback if the required features are met References: <1396622471-13114-1-git-send-email-roger.pau@citrix.com> In-Reply-To: <1396622471-13114-1-git-send-email-roger.pau@citrix.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.80.2.76] X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/04/14 15:41, Roger Pau Monne wrote: > Blkback cannot work properly on auto-translated guests if Xen doesn't > update the IOMMU when performing grant maps/unmaps, so only attach if > the newly introduced XENFEAT_hvm_gntmap_supports_iommu is found. Can you explain the problem in more detail and which guest configurations are affected? This isn't a problem that is specific to blkback, but any backend that grant maps and passes the foreign pages to a device so there needs to be a generic solution. Why can't this be fixed by having the swiotlb bounce foreign pages? > --- a/drivers/block/xen-blkback/blkback.c > +++ b/drivers/block/xen-blkback/blkback.c > @@ -1381,6 +1381,18 @@ static int __init xen_blkif_init(void) > if (!xen_domain()) > return -ENODEV; > > +#ifdef CONFIG_X86 > + if (xen_feature(XENFEAT_auto_translated_physmap) && > + !xen_feature(XENFEAT_hvm_gntmap_supports_iommu)) { > + /* > + * blkback cannot work properly on auto-translated guests > + * if grant table mappings don't update the IOMMU entries. > + */ > + pr_debug(DRV_PFX "Disabling blkback because Xen is missing feature XENFEAT_hvm_gntmap_supports_iommu\n"); > + return -ENODEV; > + } > +#endif /* CONFIG_X86 */ Why CONFIG_X86? David -- 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/