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Tsirkin" To: Jason Gunthorpe Subject: Re: [PATCH vfio 11/11] vfio/virtio: Introduce a vfio driver over virtio devices Message-ID: <20230922111342-mutt-send-email-mst@kernel.org> References: <20230921125348-mutt-send-email-mst@kernel.org> <20230921170709.GS13733@nvidia.com> <20230921131035-mutt-send-email-mst@kernel.org> <20230921174450.GT13733@nvidia.com> <20230921135426-mutt-send-email-mst@kernel.org> <20230921181637.GU13733@nvidia.com> <20230921152802-mutt-send-email-mst@kernel.org> <20230921195345.GZ13733@nvidia.com> <20230922122501.GP13733@nvidia.com> MIME-Version: 1.0 In-Reply-To: <20230922122501.GP13733@nvidia.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: kvm@vger.kernel.org, maorg@nvidia.com, virtualization@lists.linux-foundation.org, jiri@nvidia.com, leonro@nvidia.com X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; 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Tsirkin" To: Jason Gunthorpe Cc: Jason Wang , Alex Williamson , Yishai Hadas , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, parav@nvidia.com, feliu@nvidia.com, jiri@nvidia.com, kevin.tian@intel.com, joao.m.martins@oracle.com, leonro@nvidia.com, maorg@nvidia.com Subject: Re: [PATCH vfio 11/11] vfio/virtio: Introduce a vfio driver over virtio devices Message-ID: <20230922111342-mutt-send-email-mst@kernel.org> References: <20230921125348-mutt-send-email-mst@kernel.org> <20230921170709.GS13733@nvidia.com> <20230921131035-mutt-send-email-mst@kernel.org> <20230921174450.GT13733@nvidia.com> <20230921135426-mutt-send-email-mst@kernel.org> <20230921181637.GU13733@nvidia.com> <20230921152802-mutt-send-email-mst@kernel.org> <20230921195345.GZ13733@nvidia.com> <20230922122501.GP13733@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230922122501.GP13733@nvidia.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Sep 22, 2023 at 09:25:01AM -0300, Jason Gunthorpe wrote: > On Fri, Sep 22, 2023 at 11:02:50AM +0800, Jason Wang wrote: > > On Fri, Sep 22, 2023 at 3:53 AM Jason Gunthorpe wrote: > > > > > > On Thu, Sep 21, 2023 at 03:34:03PM -0400, Michael S. Tsirkin wrote: > > > > > > > that's easy/practical. If instead VDPA gives the same speed with just > > > > shadow vq then keeping this hack in vfio seems like less of a problem. > > > > Finally if VDPA is faster then maybe you will reconsider using it ;) > > > > > > It is not all about the speed. > > > > > > VDPA presents another large and complex software stack in the > > > hypervisor that can be eliminated by simply using VFIO. > > > > vDPA supports standard virtio devices so how did you define > > complexity? > > As I said, VFIO is already required for other devices in these VMs. So > anything incremental over base-line vfio-pci is complexity to > minimize. > > Everything vdpa does is either redundant or unnecessary compared to > VFIO in these environments. > > Jason Yes but you know. There are all kind of environments. I guess you consider yours the most mainstream and important, and are sure it will always stay like this. But if there's a driver that does what you need then you use that. You really should be explaining what vdpa *does not* do that you need. But anyway, if Alex wants to maintain this it's not too bad, but I would like to see more code move into a library living under the virtio directory. As it is structured now it will make virtio core development harder. -- MST