Re: [PATCH v2] hw/virtio/vhost-user: support obtain vdpa device's mac address automatically

[陈浩]

On 2022/9/22 18:19, Michael S. Tsirkin wrote:
> On Thu, Sep 22, 2022 at 11:02:56AM +0100, Alex Bennée wrote:
> > "Michael S. Tsirkin" <mst@redhat.com> writes:
> >
> > > On Wed, Sep 21, 2022 at 07:23:12PM +0100, Alex Bennée wrote:
> > > > chenh <chenh@yusur.tech> writes:
> > > >
> > > > > From: Hao Chen <chenh@yusur.tech>
> > > > >
> > > > > When use dpdk-vdpa tests vdpa device. You need to specify the mac address to
> > > > > start the virtual machine through libvirt or qemu, but now, the libvirt or
> > > > > qemu can call dpdk vdpa vendor driver's ops .get_config through 
> > > > > vhost_net_get_config
> > > > > to get the mac address of the vdpa hardware without manual configuration.
> > > > >
> > > > > v1->v2:
> > > > > Only copy ETH_ALEN data of netcfg for some vdpa device such as
> > > > > NVIDIA BLUEFIELD DPU(BF2)'s netcfg->status is not right.
> > > > > We only need the mac address and don't care about the status field.
> > > > >
> > > > > Signed-off-by: Hao Chen <chenh@yusur.tech>
> > > > > ---
> > > > >   hw/block/vhost-user-blk.c |  1 -
> > > > >   hw/net/virtio-net.c       |  7 +++++++
> > > > >   hw/virtio/vhost-user.c    | 19 -------------------
> > > > >   3 files changed, 7 insertions(+), 20 deletions(-)
> > > > >
> > > > > diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
> > > > > index 9117222456..5dca4eab09 100644
> > > > > --- a/hw/block/vhost-user-blk.c
> > > > > +++ b/hw/block/vhost-user-blk.c
> > > > > @@ -337,7 +337,6 @@ static int vhost_user_blk_connect(DeviceState *dev, Error 
> > > > > **errp)
> > > > >   
> > > > >       vhost_dev_set_config_notifier(&s->dev, &blk_ops);
> > > > >   
> > > > > -    s->vhost_user.supports_config = true;
> > > > <snip>
> > > >
> > > > NACK from me. The supports_config flag is there for a reason.
> > >
> > > Alex please, do not send NACKs. If you feel compelled to stress
> > > your point, provide extra justification instead. Thanks!
> > OK I was objecting to ripping out the common vhost-user code which was
> > implemented as a fix for behaviour found while attempting to upstream:
> >
> >    Subject: [PATCH  v4 for 7.2 00/22] virtio-gpio and various virtio cleanups
> >    Date: Tue,  2 Aug 2022 10:49:48 +0100
> >    Message-Id: <20220802095010.3330793-1-alex.bennee@linaro.org>
> >
> > I vhost-user-blk wants to suppress its use of vhost-user config messages
> > I guess that should be a control option but it sounds like a buggy
> > back-end.
> Thanks for the review!

QEMU needs to obtain the mac address of the underlying vdpa hardware 
through the 'vhost_user_get_config' function, but this part of the check 
of virtio_blk makes 'vhost_user_get_config' unusable in virtio-net, 
because 'vhost_user_get_config' depends on the 
VHOST_USER_PROTOCOL_F_CONFIG feature, which is the key point of the 
problem.

Currently I only need to use 'vhost_user_get_config' function, it seems 
not necessary to implement dev->config_ops && 
dev->config_ops->vhost_dev_config_notifier in virtio-net.

Can this part of the checks be moved elsewhere? I don't know how to skip 
this part of the virtio blk related checks to achieve my functionality, 
so I removed those checks. 🙁

> > > > >   
> > > > > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> > > > > index bd24741be8..8b01078249 100644
> > > > > --- a/hw/virtio/vhost-user.c
> > > > > +++ b/hw/virtio/vhost-user.c
> > > > > @@ -2013,8 +2013,6 @@ static int vhost_user_backend_init(struct vhost_dev *dev, 
> > > > > void *opaque,
> > > > >       }
> > > > >   
> > > > >       if (virtio_has_feature(features, VHOST_USER_F_PROTOCOL_FEATURES)) {
> > > > > -        bool supports_f_config = vus->supports_config ||
> > > > > -            (dev->config_ops && dev->config_ops->vhost_dev_config_notifier);
> > > > >           uint64_t protocol_features;
> > > > >   
> > > > >           dev->backend_features |= 1ULL << VHOST_USER_F_PROTOCOL_FEATURES;
> > > > > @@ -2033,23 +2031,6 @@ static int vhost_user_backend_init(struct vhost_dev 
> > > > > *dev, void *opaque,
> > > > >            */
> > > > >           protocol_features &= VHOST_USER_PROTOCOL_FEATURE_MASK;
> > > > >   
> > > > > -        if (supports_f_config) {
> > > > > -            if (!virtio_has_feature(protocol_features,
> > > > > -                                    VHOST_USER_PROTOCOL_F_CONFIG)) {
> > > > > -                error_setg(errp, "vhost-user device expecting "
> > > > > -                           "VHOST_USER_PROTOCOL_F_CONFIG but the vhost-user backend 
> > > > > does "
> > > > > -                           "not support it.");
> > > > > -                return -EPROTO;
> > > > > -            }
> > > > > -        } else {
> > > > > -            if (virtio_has_feature(protocol_features,
> > > > > -                                   VHOST_USER_PROTOCOL_F_CONFIG)) {
> > > > > -                warn_reportf_err(*errp, "vhost-user backend supports "
> > > > > -                                 "VHOST_USER_PROTOCOL_F_CONFIG but QEMU does 
> > > > > not.");
> > > > > -                protocol_features &= ~(1ULL << VHOST_USER_PROTOCOL_F_CONFIG);
> > > > > -            }
> > > > > -        }
> > > > > -
> > > > >           /* final set of protocol features */
> > > > >           dev->protocol_features = protocol_features;
> > > > >           err = vhost_user_set_protocol_features(dev, dev->protocol_features);
> > > >
> > > > --
> > > > Alex Bennée
> >
> > --
> > Alex Bennée