On Tue, Mar 19, 2024 at 11:00 AM Kevin Wolf <kw...@redhat.com> wrote: > > Am 18.03.2024 um 20:27 hat Eugenio Perez Martin geschrieben: > > On Mon, Mar 18, 2024 at 10:02 AM Michael S. Tsirkin <m...@redhat.com> wrote: > > > > > > 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? > > > > > > > We have the VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK backend flag, > > right. If the backend does not offer it, it is better to enable all > > the queues here and add a migration blocker in net/vhost-vdpa.c. > > > > So the check should be: > > nc->info->type == VHOST_VDPA && (backend_features & > > VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK). > > > > I can manage to add the migration blocker on top of this patch. > > Note that my patch preserves the current behaviour for vhost_net. The > callback wasn't implemented for vdpa so far, so we never called anything > even if the flag wasn't set. This patch adds an implementation for the > callback, so we have to skip it here to have everything in vhost_net > work as before - which is what the condition as written does. > > If we add a check for the flag now (I don't know if that's correct or > not), that would be a second, unrelated change of behaviour in the same > patch. So if it's necessary, that's a preexisting problem and I'd argue > it doesn't belong in this patch, but should be done separately. >
Right, that's a very good point. I'll add proper checking on top of your patch when it is merged. Reviewed-by: Eugenio Pérez <epere...@redhat.com> Thanks!