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vhost: enable vrings in vhost_dev_start() for vhost-user devices

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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 <gmaglione@redhat.com>
Tested-by: German Maglione <gmaglione@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Message-Id: <20221123131630.52020-1-sgarzare@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20221130112439.2527228-3-alex.bennee@linaro.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Stefano Garzarella
2022-11-30 11:24:36 +00:00
committed by Michael S. Tsirkin
parent 523e40022f
commit 4daa5054c5
13 changed files with 67 additions and 31 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
backends/cryptodev-vhost.c
View File

@ -94,7 +94,7 @@ cryptodev_vhost_start_one(CryptoDevBackendVhost *crypto,
goto fail_notifiers;
}
r = vhost_dev_start(&crypto->dev, dev);
r = vhost_dev_start(&crypto->dev, dev, false);
if (r < 0) {
goto fail_start;
}
@ -111,7 +111,7 @@ static void
cryptodev_vhost_stop_one(CryptoDevBackendVhost *crypto,
VirtIODevice *dev)
{
vhost_dev_stop(&crypto->dev, dev);
vhost_dev_stop(&crypto->dev, dev, false);
vhost_dev_disable_notifiers(&crypto->dev, dev);
}