On Mon, Mar 18, 2024 at 12:31:26PM +0800, Jason Wang wrote: > On Fri, Mar 15, 2024 at 11:59 PM Kevin Wolf <kw...@redhat.com> wrote: > > > > 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-sta...@nongnu.org > > Fixes: 6c4825476a4351530bcac17abab72295b75ffe98 > > Signed-off-by: Kevin Wolf <kw...@redhat.com> > > --- > > v2: > > - Actually make use of the @enable parameter > > - Change vhost_net to preserve the current behaviour > > > > v3: > > - Updated trace point [Stefano] > > - Fixed typo in comment [Stefano] > > > > hw/net/vhost_net.c | 10 ++++++++++ > > hw/virtio/vdpa-dev.c | 5 +---- > > hw/virtio/vhost-vdpa.c | 29 ++++++++++++++++++++++++++--- > > hw/virtio/vhost.c | 8 +++++++- > > hw/virtio/trace-events | 2 +- > > 5 files changed, 45 insertions(+), 9 deletions(-) > > > > diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c > > index e8e1661646..fd1a93701a 100644 > > --- a/hw/net/vhost_net.c > > +++ b/hw/net/vhost_net.c > > @@ -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; > > + } > > I think we need some inputs from Eugenio, this is only needed for > shadow virtqueue during live migration but not other cases. > > Thanks
Yes I think we had a backend flag for this, right? Eugenio can you comment please?