linux-kernel - Re: [PATCH V3 6/6] vDPA/ifcvf: verify mandatory feature bits for vDPA

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Message-ID: <4f3ef2bb-d823-d53d-3bb0-0152a3f6c9f1@redhat.com>
Date:   Thu, 11 Mar 2021 14:20:46 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Zhu Lingshan <lingshan.zhu@...ux.intel.com>,
        Zhu Lingshan <lingshan.zhu@...el.com>, mst@...hat.com,
        lulu@...hat.com, leonro@...dia.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH V3 6/6] vDPA/ifcvf: verify mandatory feature bits for vDPA

On 2021/3/11 12:16 下午, Zhu Lingshan wrote:
>
>
> On 3/11/2021 11:20 AM, Jason Wang wrote:
>>
>> On 2021/3/10 5:00 下午, Zhu Lingshan wrote:
>>> vDPA requres VIRTIO_F_ACCESS_PLATFORM as a must, this commit
>>> examines this when set features.
>>>
>>> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
>>> ---
>>>   drivers/vdpa/ifcvf/ifcvf_base.c | 8 ++++++++
>>>   drivers/vdpa/ifcvf/ifcvf_base.h | 1 +
>>>   drivers/vdpa/ifcvf/ifcvf_main.c | 5 +++++
>>>   3 files changed, 14 insertions(+)
>>>
>>> diff --git a/drivers/vdpa/ifcvf/ifcvf_base.c 
>>> b/drivers/vdpa/ifcvf/ifcvf_base.c
>>> index ea6a78791c9b..58f47fdce385 100644
>>> --- a/drivers/vdpa/ifcvf/ifcvf_base.c
>>> +++ b/drivers/vdpa/ifcvf/ifcvf_base.c
>>> @@ -224,6 +224,14 @@ u64 ifcvf_get_features(struct ifcvf_hw *hw)
>>>       return hw->hw_features;
>>>   }
>>>   +int ifcvf_verify_min_features(struct ifcvf_hw *hw)
>>> +{
>>> +    if (!(hw->hw_features & BIT_ULL(VIRTIO_F_ACCESS_PLATFORM)))
>>> +        return -EINVAL;
>>> +
>>> +    return 0;
>>> +}
>>> +
>>>   void ifcvf_read_net_config(struct ifcvf_hw *hw, u64 offset,
>>>                  void *dst, int length)
>>>   {
>>> diff --git a/drivers/vdpa/ifcvf/ifcvf_base.h 
>>> b/drivers/vdpa/ifcvf/ifcvf_base.h
>>> index dbb8c10aa3b1..91c5735d4dc9 100644
>>> --- a/drivers/vdpa/ifcvf/ifcvf_base.h
>>> +++ b/drivers/vdpa/ifcvf/ifcvf_base.h
>>> @@ -123,6 +123,7 @@ void io_write64_twopart(u64 val, u32 *lo, u32 *hi);
>>>   void ifcvf_reset(struct ifcvf_hw *hw);
>>>   u64 ifcvf_get_features(struct ifcvf_hw *hw);
>>>   u64 ifcvf_get_hw_features(struct ifcvf_hw *hw);
>>> +int ifcvf_verify_min_features(struct ifcvf_hw *hw);
>>>   u16 ifcvf_get_vq_state(struct ifcvf_hw *hw, u16 qid);
>>>   int ifcvf_set_vq_state(struct ifcvf_hw *hw, u16 qid, u16 num);
>>>   struct ifcvf_adapter *vf_to_adapter(struct ifcvf_hw *hw);
>>> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c 
>>> b/drivers/vdpa/ifcvf/ifcvf_main.c
>>> index 25fb9dfe23f0..f624f202447d 100644
>>> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
>>> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
>>> @@ -179,6 +179,11 @@ static u64 ifcvf_vdpa_get_features(struct 
>>> vdpa_device *vdpa_dev)
>>>   static int ifcvf_vdpa_set_features(struct vdpa_device *vdpa_dev, 
>>> u64 features)
>>>   {
>>>       struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev);
>>> +    int ret;
>>> +
>>> +    ret = ifcvf_verify_min_features(vf);
>>
>>
>> So this validate device features instead of driver which is the one 
>> we really want to check?
>>
>> Thanks
>
> Hi Jason,
>
> Here we check device feature bits to make sure the device support 
> ACCESS_PLATFORM. 

If you want to check device features, you need to do that during probe() 
and fail the probing if without the feature. But I think you won't ship 
cards without ACCESS_PLATFORM.

> In get_features(),
> it will return a intersection of device features bit and driver 
> supported features bits(which includes ACCESS_PLATFORM).
> Other components like QEMU should not set features bits more than this 
> intersection of bits. so we can make sure if this
> ifcvf_verify_min_features() passed, both device and driver support 
> ACCESS_PLATFORM.
>
> Are you suggesting check driver feature bits in 
> ifcvf_verify_min_features() in the meantime as well?

So it really depends on your hardware. If you hardware can always offer 
ACCESS_PLATFORM, you just need to check driver features. This is how 
vdpa_sim and mlx5_vdpa work.

Thanks

>
> Thanks！
>>
>>
>>> +    if (ret)
>>> +        return ret;
>>>         vf->req_features = features;
>>
>> _______________________________________________
>> Virtualization mailing list
>> Virtualization@...ts.linux-foundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/virtualization
>

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