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vdpa-dev: Fix initialisation order to restore VDUSE compatibility

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VDUSE requires that virtqueues are first enabled before the DRIVER_OK
status flag is set; with the current API of the kernel module, it is
impossible to enable the opposite order in our block export code because
userspace is not notified when a virtqueue is enabled.

This requirement also mathces the normal initialisation order as done by
the generic vhost code in QEMU. However, commit 6c482547 accidentally
changed the order for vdpa-dev and broke access to VDUSE devices with
this.

This changes vdpa-dev to use the normal order again and use the standard
vhost callback .vhost_set_vring_enable for this. VDUSE devices can be
used with vdpa-dev again after this fix.

vhost_net intentionally avoided enabling the vrings for vdpa and does
this manually later while it does enable them for other vhost backends.
Reflect this in the vhost_net code and return early for vdpa, so that
the behaviour doesn't change for this device.

Cc: qemu-stable@nongnu.org
Fixes: 6c4825476a ('vdpa: move vhost_vdpa_set_vring_ready to the caller')
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20240315155949.86066-1-kwolf@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2024-03-15 16:59:49 +01:00
parent d9e4070603
commit 2c66de61f8
5 changed files with 45 additions and 9 deletions
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10
hw/net/vhost_net.c
View file

@ -541,6 +541,16 @@ int vhost_set_vring_enable(NetClientState *nc, int enable)
VHostNetState *net = get_vhost_net(nc);
const VhostOps *vhost_ops = net->dev.vhost_ops;
/*
* vhost-vdpa network devices need to enable dataplane virtqueues after
* DRIVER_OK, so they can recover device state before starting dataplane.
* Because of that, we don't enable virtqueues here and leave it to
* net/vhost-vdpa.c.
*/
if (nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) {
return 0;
}
nc->vring_enable = enable;
if (vhost_ops && vhost_ops->vhost_set_vring_enable) {