From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH v2] intel-iommu: Default to non-coherent for domains unattached to iommus Date: Tue, 18 Sep 2012 13:58:02 +0200 Message-ID: <20120918115802.GJ2505@amd.com> References: <20111112002421.10875.8307.stgit@bling.home> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Return-path: Content-Disposition: inline In-Reply-To: <20111112002421.10875.8307.stgit@bling.home> Sender: linux-pci-owner@vger.kernel.org To: Alex Williamson Cc: dwmw2@infradead.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, chrisw@sous-sol.org, iommu@lists.linux-foundation.org List-Id: iommu@lists.linux-foundation.org On Fri, Nov 11, 2011 at 05:26:44PM -0700, Alex Williamson wrote: > domain_update_iommu_coherency() currently defaults to setting domains > as coherent when the domain is not attached to any iommus. This > allows for a window in domain_context_mapping_one() where such a > domain can update context entries non-coherently, and only after > update the domain capability to clear iommu_coherency. > > This can be seen using KVM device assignment on VT-d systems that > do not support coherency in the ecap register. When a device is > added to a guest, a domain is created (iommu_coherency = 0), the > device is attached, and ranges are mapped. If we then hot unplug > the device, the coherency is updated and set to the default (1) > since no iommus are attached to the domain. A subsequent attach > of a device makes use of the same dmar domain (now marked coherent) > updates context entries with coherency enabled, and only disables > coherency as the last step in the process. > > To fix this, switch domain_update_iommu_coherency() to use the > safer, non-coherent default for domains not attached to iommus. > > Signed-off-by: Alex Williamson > Tested-by: Donald Dutile > Acked-by: Donald Dutile > Acked-by: Chris Wright Applied, thanks. -- AMD Operating System Research Center Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach General Managers: Alberto Bozzo Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from tx2ehsobe003.messaging.microsoft.com ([65.55.88.13]:43226 "EHLO tx2outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751574Ab2IRL6L (ORCPT ); Tue, 18 Sep 2012 07:58:11 -0400 Date: Tue, 18 Sep 2012 13:58:02 +0200 From: Joerg Roedel To: Alex Williamson CC: , , , , Subject: Re: [PATCH v2] intel-iommu: Default to non-coherent for domains unattached to iommus Message-ID: <20120918115802.GJ2505@amd.com> References: <20111112002421.10875.8307.stgit@bling.home> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" In-Reply-To: <20111112002421.10875.8307.stgit@bling.home> Sender: linux-pci-owner@vger.kernel.org List-ID: On Fri, Nov 11, 2011 at 05:26:44PM -0700, Alex Williamson wrote: > domain_update_iommu_coherency() currently defaults to setting domains > as coherent when the domain is not attached to any iommus. This > allows for a window in domain_context_mapping_one() where such a > domain can update context entries non-coherently, and only after > update the domain capability to clear iommu_coherency. > > This can be seen using KVM device assignment on VT-d systems that > do not support coherency in the ecap register. When a device is > added to a guest, a domain is created (iommu_coherency = 0), the > device is attached, and ranges are mapped. If we then hot unplug > the device, the coherency is updated and set to the default (1) > since no iommus are attached to the domain. A subsequent attach > of a device makes use of the same dmar domain (now marked coherent) > updates context entries with coherency enabled, and only disables > coherency as the last step in the process. > > To fix this, switch domain_update_iommu_coherency() to use the > safer, non-coherent default for domains not attached to iommus. > > Signed-off-by: Alex Williamson > Tested-by: Donald Dutile > Acked-by: Donald Dutile > Acked-by: Chris Wright Applied, thanks. -- AMD Operating System Research Center Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach General Managers: Alberto Bozzo Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632