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Wed, 09 Dec 2020 04:00:55 -0800 (PST) X-Google-Smtp-Source: ABdhPJwcJSG02TAyUTW+VNdiN2re1N9kAh2N75Xi7v7CXyvg3kf2iqP7u2vinBaagIz7uHe3uMaKmoLrXvjkvH01MEM= X-Received: by 2002:ae9:dcc1:: with SMTP id q184mr2482593qkf.425.1607515255708; Wed, 09 Dec 2020 04:00:55 -0800 (PST) MIME-Version: 1.0 References: <20201120185105.279030-1-eperezma@redhat.com> <20201120185105.279030-5-eperezma@redhat.com> <20201207164323.GK203660@stefanha-x1.localdomain> In-Reply-To: <20201207164323.GK203660@stefanha-x1.localdomain> From: Eugenio Perez Martin Date: Wed, 9 Dec 2020 13:00:19 +0100 Message-ID: Subject: Re: [RFC PATCH 04/27] vhost: add vhost_kernel_set_vring_enable To: Stefan Hajnoczi Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eperezma@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=216.205.24.124; envelope-from=eperezma@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=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: kvm list , "Michael S. Tsirkin" , Jason Wang , qemu-level , Daniel Daly , virtualization@lists.linux-foundation.org, Liran Alon , Eli Cohen , Nitin Shrivastav , Alex Barba , Christophe Fontaine , Juan Quintela , Lee Ballard , Lars Ganrot , Rob Miller , Stefano Garzarella , Howard Cai , Parav Pandit , vm , Salil Mehta , Stephen Finucane , Xiao W Wang , Sean Mooney , Stefan Hajnoczi , Jim Harford , Dmytro Kazantsev , Siwei Liu , Harpreet Singh Anand , Michael Lilja , Max Gurtovoy Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Dec 7, 2020 at 5:43 PM Stefan Hajnoczi wrote: > > On Fri, Nov 20, 2020 at 07:50:42PM +0100, Eugenio P=C3=A9rez wrote: > > Signed-off-by: Eugenio P=C3=A9rez > > --- > > hw/virtio/vhost-backend.c | 29 +++++++++++++++++++++++++++++ > > 1 file changed, 29 insertions(+) > > > > diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c > > index 222bbcc62d..317f1f96fa 100644 > > --- a/hw/virtio/vhost-backend.c > > +++ b/hw/virtio/vhost-backend.c > > @@ -201,6 +201,34 @@ static int vhost_kernel_get_vq_index(struct vhost_= dev *dev, int idx) > > return idx - dev->vq_index; > > } > > > > +static int vhost_kernel_set_vq_enable(struct vhost_dev *dev, unsigned = idx, > > + bool enable) > > +{ > > + struct vhost_vring_file file =3D { > > + .index =3D idx, > > + }; > > + > > + if (!enable) { > > + file.fd =3D -1; /* Pass -1 to unbind from file. */ > > + } else { > > + struct vhost_net *vn_dev =3D container_of(dev, struct vhost_ne= t, dev); > > + file.fd =3D vn_dev->backend; > > + } > > + > > + return vhost_kernel_net_set_backend(dev, &file); > > This is vhost-net specific even though the function appears to be > generic. Is there a plan to extend this to all devices? > I expected each vhost backend to enable-disable in its own terms, but I think it could be 100% virtio-device generic with something like the device state capability: https://lists.oasis-open.org/archives/virtio-comment/202012/msg00005.html . > > +} > > + > > +static int vhost_kernel_set_vring_enable(struct vhost_dev *dev, int en= able) > > +{ > > + int i; > > + > > + for (i =3D 0; i < dev->nvqs; ++i) { > > + vhost_kernel_set_vq_enable(dev, i, enable); > > + } > > + > > + return 0; > > +} > > I suggest exposing the per-vq interface (vhost_kernel_set_vq_enable()) > in VhostOps so it follows the ioctl interface. It was actually the initial plan, I left as all-or-nothing to make less cha= nges. > vhost_kernel_set_vring_enable() can be moved to vhost.c can loop over > all vqs if callers find it convenient to loop over all vqs. I'm ok with it. Thinking out loud, I don't know if it is easier for some devices to enable/disable all of it (less syscalls? less downtime somehow?) but I find more generic and useful the per-virtqueue approach. Thanks!