netdev - Re: [PATCH 2/4] vDPA: only report driver features if FEATURES

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Date:   Wed, 21 Sep 2022 15:53:28 +0800
From:   "Zhu, Lingshan" <lingshan.zhu@...el.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     mst <mst@...hat.com>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        netdev <netdev@...r.kernel.org>, kvm <kvm@...r.kernel.org>
Subject: Re: [PATCH 2/4] vDPA: only report driver features if FEATURES_OK is
 set



On 9/21/2022 3:43 PM, Jason Wang wrote:
> On Wed, Sep 21, 2022 at 1:39 PM Zhu, Lingshan <lingshan.zhu@...el.com> wrote:
>>
>>
>> On 9/21/2022 10:14 AM, Jason Wang wrote:
>>> On Tue, Sep 20, 2022 at 1:46 PM Zhu, Lingshan <lingshan.zhu@...el.com> wrote:
>>>>
>>>> On 9/20/2022 10:16 AM, Jason Wang wrote:
>>>>> On Fri, Sep 9, 2022 at 5:05 PM Zhu Lingshan <lingshan.zhu@...el.com> wrote:
>>>>>> vdpa_dev_net_config_fill() should only report driver features
>>>>>> to userspace after features negotiation is done.
>>>>>>
>>>>>> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
>>>>>> ---
>>>>>>     drivers/vdpa/vdpa.c | 13 +++++++++----
>>>>>>     1 file changed, 9 insertions(+), 4 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
>>>>>> index 798a02c7aa94..29d7e8858e6f 100644
>>>>>> --- a/drivers/vdpa/vdpa.c
>>>>>> +++ b/drivers/vdpa/vdpa.c
>>>>>> @@ -819,6 +819,7 @@ static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *ms
>>>>>>            struct virtio_net_config config = {};
>>>>>>            u64 features_device, features_driver;
>>>>>>            u16 val_u16;
>>>>>> +       u8 status;
>>>>>>
>>>>>>            vdev->config->get_config(vdev, 0, &config, sizeof(config));
>>>>>>
>>>>>> @@ -834,10 +835,14 @@ static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *ms
>>>>>>            if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MTU, val_u16))
>>>>>>                    return -EMSGSIZE;
>>>>>>
>>>>>> -       features_driver = vdev->config->get_driver_features(vdev);
>>>>>> -       if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_NEGOTIATED_FEATURES, features_driver,
>>>>>> -                             VDPA_ATTR_PAD))
>>>>>> -               return -EMSGSIZE;
>>>>>> +       /* only read driver features after the feature negotiation is done */
>>>>>> +       status = vdev->config->get_status(vdev);
>>>>>> +       if (status & VIRTIO_CONFIG_S_FEATURES_OK) {
>>>>> Any reason this is not checked in its caller as what it used to do before?
>>>> will check the existence of vdev->config->get_status before calling it in V2
>>> Just to clarify, I meant to check FEAUTRES_OK in the caller -
>>> vdpa_dev_config_fill() otherwise each type needs to repeat this in
>>> their specific codes.
>> if we check FEATURES_OK in the caller vdpa_dev_config_fill(), then
>> !FEATURES_OK will block reporting all attributions, for example
>> the device features and virtio device config space fields in this series
>> and device status.
>> Currently only driver features needs to check FEATURES_OK.
>> Or did I missed anything?
> I don't see much difference, we just move the following part to the
> caller, it is not the config but the VDPA_ATTR_DEV_NEGOTIATED_FEATURES
> is blocked.
OK, I get you. V2 will check FEATURES_OK and report driver features in 
vdpa_dev_config_fill()

Thanks
Zhu Lingshan
>
> Thanks
>
>> Thanks
>>> Thanks
>>>
>>>> Thanks,
>>>> Zhu Lingshan
>>>>> Thanks
>>>>>
>>>>>> +               features_driver = vdev->config->get_driver_features(vdev);
>>>>>> +               if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_NEGOTIATED_FEATURES, features_driver,
>>>>>> +                                     VDPA_ATTR_PAD))
>>>>>> +                       return -EMSGSIZE;
>>>>>> +       }
>>>>>>
>>>>>>            features_device = vdev->config->get_device_features(vdev);
>>>>>>
>>>>>> --
>>>>>> 2.31.1
>>>>>>