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

[陈浩 <chenh@yusur.tech>]

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