From 4daa5054c599c8aec70f1264a01341a15921c145 Mon Sep 17 00:00:00 2001 From: Stefano Garzarella Date: Wed, 30 Nov 2022 11:24:36 +0000 Subject: vhost: enable vrings in vhost_dev_start() for vhost-user devices Commit 02b61f38d3 ("hw/virtio: incorporate backend features in features") properly negotiates VHOST_USER_F_PROTOCOL_FEATURES with the vhost-user backend, but we forgot to enable vrings as specified in docs/interop/vhost-user.rst: If ``VHOST_USER_F_PROTOCOL_FEATURES`` has not been negotiated, the ring starts directly in the enabled state. If ``VHOST_USER_F_PROTOCOL_FEATURES`` has been negotiated, the ring is initialized in a disabled state and is enabled by ``VHOST_USER_SET_VRING_ENABLE`` with parameter 1. Some vhost-user front-ends already did this by calling vhost_ops.vhost_set_vring_enable() directly: - backends/cryptodev-vhost.c - hw/net/virtio-net.c - hw/virtio/vhost-user-gpio.c But most didn't do that, so we would leave the vrings disabled and some backends would not work. We observed this issue with the rust version of virtiofsd [1], which uses the event loop [2] provided by the vhost-user-backend crate where requests are not processed if vring is not enabled. Let's fix this issue by enabling the vrings in vhost_dev_start() for vhost-user front-ends that don't already do this directly. Same thing also in vhost_dev_stop() where we disable vrings. [1] https://gitlab.com/virtio-fs/virtiofsd [2] https://github.com/rust-vmm/vhost/blob/240fc2966/crates/vhost-user-backend/src/event_loop.rs#L217 Fixes: 02b61f38d3 ("hw/virtio: incorporate backend features in features") Reported-by: German Maglione Tested-by: German Maglione Signed-off-by: Stefano Garzarella Acked-by: Raphael Norwitz Message-Id: <20221123131630.52020-1-sgarzare@redhat.com> Signed-off-by: Alex Bennée Reviewed-by: Michael S. Tsirkin Message-Id: <20221130112439.2527228-3-alex.bennee@linaro.org> Signed-off-by: Michael S. Tsirkin --- include/hw/virtio/vhost.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h index 353252ac3e..67a6807fac 100644 --- a/include/hw/virtio/vhost.h +++ b/include/hw/virtio/vhost.h @@ -184,24 +184,26 @@ static inline bool vhost_dev_is_started(struct vhost_dev *hdev) * vhost_dev_start() - start the vhost device * @hdev: common vhost_dev structure * @vdev: the VirtIODevice structure + * @vrings: true to have vrings enabled in this call * * Starts the vhost device. From this point VirtIO feature negotiation * can start and the device can start processing VirtIO transactions. * * Return: 0 on success, < 0 on error. */ -int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev); +int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings); /** * vhost_dev_stop() - stop the vhost device * @hdev: common vhost_dev structure * @vdev: the VirtIODevice structure + * @vrings: true to have vrings disabled in this call * * Stop the vhost device. After the device is stopped the notifiers * can be disabled (@vhost_dev_disable_notifiers) and the device can * be torn down (@vhost_dev_cleanup). */ -void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev); +void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings); /** * DOC: vhost device configuration handling -- cgit v1.2.3-55-g7522