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Tsirkin" To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, Cindy Lu Subject: Re: [PATCH] vhost-user: send SET_STATUS 0 after GET_VRING_BASE Message-ID: <20230421013936-mutt-send-email-mst@kernel.org> References: <20230420130706.541219-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230420130706.541219-1-stefanha@redhat.com> Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@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, DKIMWL_WL_HIGH=-0.001, 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_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, Apr 20, 2023 at 09:07:06AM -0400, Stefan Hajnoczi wrote: > Setting the VIRTIO Device Status Field to 0 resets the device. The > device's state is lost, including the vring configuration. > > vhost-user.c currently sends SET_STATUS 0 before GET_VRING_BASE. This > risks confusion about the lifetime of the vhost-user state (e.g. vring > last_avail_idx) across VIRTIO device reset. > > Eugenio Pérez adjusted the order for vhost-vdpa.c > in commit c3716f260bff ("vdpa: move vhost reset after get vring base") > and in that commit description suggested doing the same for vhost-user > in the future. > > Go ahead and adjust vhost-user.c now. I ran various online code searches > to identify vhost-user backends implementing SET_STATUS. It seems only > DPDK implements SET_STATUS and Yajun Wu has > confirmed that it is safe to make this change. Fixes tag? > Cc: Michael S. Tsirkin > Cc: Cindy Lu > Signed-off-by: Stefan Hajnoczi > --- > hw/virtio/vhost-user.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c > index e5285df4ba..2d40b1b3e7 100644 > --- a/hw/virtio/vhost-user.c > +++ b/hw/virtio/vhost-user.c > @@ -2677,10 +2677,20 @@ static int vhost_user_dev_start(struct vhost_dev *dev, bool started) > VIRTIO_CONFIG_S_DRIVER | > VIRTIO_CONFIG_S_DRIVER_OK); > } else { > - return vhost_user_set_status(dev, 0); > + return 0; > } > } > > +static void vhost_user_reset_status(struct vhost_dev *dev) > +{ > + /* Set device status only for last queue pair */ > + if (dev->vq_index + dev->nvqs != dev->vq_index_end) { > + return; > + } > + > + vhost_user_set_status(dev, 0); > +} > + > const VhostOps user_ops = { > .backend_type = VHOST_BACKEND_TYPE_USER, > .vhost_backend_init = vhost_user_backend_init, > @@ -2716,4 +2726,5 @@ const VhostOps user_ops = { > .vhost_get_inflight_fd = vhost_user_get_inflight_fd, > .vhost_set_inflight_fd = vhost_user_set_inflight_fd, > .vhost_dev_start = vhost_user_dev_start, > + .vhost_reset_status = vhost_user_reset_status, > }; > -- > 2.39.2