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[174.93.89.182]) by smtp.gmail.com with ESMTPSA id r17sm14970427qta.78.2021.02.08.10.37.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Feb 2021 10:37:22 -0800 (PST) Date: Mon, 8 Feb 2021 13:37:21 -0500 From: Peter Xu To: Jason Wang Subject: Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support Message-ID: <20210208183721.GB68242@xz-x1> References: <20210204191228.187550-1-peterx@redhat.com> <2382a93d-41c1-24fd-144f-87ee18171bc9@redhat.com> <213acf9a-d1c0-3a1d-4846-877d90fadc03@redhat.com> <20210205153107.GX6468@xz-x1> MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=63.128.21.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.57, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jean-Philippe Brucker , Auger Eric , "Michael S . Tsirkin" , qemu-devel@nongnu.org, Eugenio Perez Martin Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Feb 08, 2021 at 11:21:23AM +0800, Jason Wang wrote: [...] > > I'm not sure I remember it right, but we seem to have similar discussion > > previously on "what if the user didn't specify ats=on" - I think at that time > > the conclusion was that we ignore the failure since that's not a valid > > configuration for qemu. > > > Yes, but I think I was wrong at that time. I can't say you're wrong - I actually still agree with you that at least there's a priority of things we'd do, and this one is not extremely important if that's not a major use case (say, if you will 100% always suggest an user to use ats=on for a viommu enabled vhost). > > > > The other issue I'm worried is (I think I mentioned it somewhere, but just to > > double confirm): I'd like to make sure SMMU and virtio-iommu are the only IOMMU > > platform that will use vhost. > > > For upstream, it won't be easy :) Sorry I definitely didn't make myself clear... :) To be explicit, does ppc use vhost kernel too? Since I know at least ppc has its own translation unit and its iommu notifier in qemu, so I'm unsure whether the same patch would break ppc too, because vhost could also ignore all UNMAP sent by the ppc vIOMMU. > > > > Otherwise IIUC we need to fix those vIOMMUs too. > > > Right, last time I check AMD IOMMU emulation, it simply trigger device IOTLB > invalidation during IOTLB invalidation which looks wrong. I did quickly grep IOMMU_NOTIFIER_UNMAP in amd_iommu.c and saw nothing. It seems amd iommu is not ready for any kind of IOMMU notifiers yet. Thanks, -- Peter Xu