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

[Michael S. Tsirkin]

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!

> >
> >> >  
> >> > 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