linux-kernel - Re: [RFC 2/2] vhost: IFC VF vdpa layer

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Message-ID: <b2adaab0-bbc3-b7f0-77da-e1e3cab93b76@redhat.com>
Date:   Tue, 22 Oct 2019 21:05:57 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Zhu Lingshan <lingshan.zhu@...ux.intel.com>,
        "Zhu, Lingshan" <lingshan.zhu@...el.com>, mst@...hat.com,
        alex.williamson@...hat.com
Cc:     linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        netdev@...r.kernel.org, dan.daly@...el.com,
        cunming.liang@...el.com, tiwei.bie@...el.com, jason.zeng@...el.com,
        zhiyuan.lv@...el.com
Subject: Re: [RFC 2/2] vhost: IFC VF vdpa layer


On 2019/10/22 下午2:53, Zhu Lingshan wrote:
>
> On 10/21/2019 6:19 PM, Jason Wang wrote:
>>
>> On 2019/10/21 下午5:53, Zhu, Lingshan wrote:
>>>
>>> On 10/16/2019 6:19 PM, Jason Wang wrote:
>>>>
>>>> On 2019/10/16 上午9:30, Zhu Lingshan wrote:
>>>>> This commit introduced IFC VF operations for vdpa, which complys to
>>>>> vhost_mdev interfaces, handles IFC VF initialization,
>>>>> configuration and removal.
>>>>>
>>>>> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
>>>>> ---


[...]


>>
>>
>>>
>>>>
>>>>
>>>>> +}
>>>>> +
>>>>> +static int ifcvf_mdev_set_features(struct mdev_device *mdev, u64 
>>>>> features)
>>>>> +{
>>>>> +    struct ifcvf_adapter *adapter = mdev_get_drvdata(mdev);
>>>>> +    struct ifcvf_hw *vf = IFC_PRIVATE_TO_VF(adapter);
>>>>> +
>>>>> +    vf->req_features = features;
>>>>> +
>>>>> +    return 0;
>>>>> +}
>>>>> +
>>>>> +static u64 ifcvf_mdev_get_vq_state(struct mdev_device *mdev, u16 
>>>>> qid)
>>>>> +{
>>>>> +    struct ifcvf_adapter *adapter = mdev_get_drvdata(mdev);
>>>>> +    struct ifcvf_hw *vf = IFC_PRIVATE_TO_VF(adapter);
>>>>> +
>>>>> +    return vf->vring[qid].last_avail_idx;
>>>>
>>>>
>>>> Does this really work? I'd expect it should be fetched from hw 
>>>> since it's an internal state.
>>> for now, it's working, we intend to support LM in next version drivers.
>>
>>
>> I'm not sure I understand here, I don't see any synchronization 
>> between the hardware and last_avail_idx, so last_avail_idx should not 
>> change.
>>
>> Btw, what did "LM" mean :) ?
>
> I can add bar IO operations here, LM = live migration, sorry for the 
> abbreviation.


Just make sure I understand here, I believe you mean reading 
last_avail_idx through IO bar here?

Thanks