netdev - Re: [PATCH 1/3] vDPA/ifcvf: deduce VIRTIO device ID when probe

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Message-ID: <e2e5de78-9b6f-32cf-5955-ed930365d79f@linux.intel.com>
Date:   Thu, 15 Apr 2021 15:23:01 +0800
From:   Zhu Lingshan <lingshan.zhu@...ux.intel.com>
To:     Jason Wang <jasowang@...hat.com>,
        Zhu Lingshan <lingshan.zhu@...el.com>, mst@...hat.com,
        lulu@...hat.com, leonro@...dia.com
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] vDPA/ifcvf: deduce VIRTIO device ID when probe



On 4/15/2021 3:16 PM, Jason Wang wrote:
>
> 在 2021/4/15 下午2:36, Zhu Lingshan 写道:
>>
>>
>> On 4/15/2021 2:30 PM, Jason Wang wrote:
>>>
>>> 在 2021/4/15 下午1:52, Zhu Lingshan 写道:
>>>>
>>>>
>>>> On 4/15/2021 11:30 AM, Jason Wang wrote:
>>>>>
>>>>> 在 2021/4/14 下午5:18, Zhu Lingshan 写道:
>>>>>> This commit deduces VIRTIO device ID as device type when probe,
>>>>>> then ifcvf_vdpa_get_device_id() can simply return the ID.
>>>>>> ifcvf_vdpa_get_features() and ifcvf_vdpa_get_config_size()
>>>>>> can work properly based on the device ID.
>>>>>>
>>>>>> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
>>>>>> ---
>>>>>>   drivers/vdpa/ifcvf/ifcvf_base.h |  1 +
>>>>>>   drivers/vdpa/ifcvf/ifcvf_main.c | 22 ++++++++++------------
>>>>>>   2 files changed, 11 insertions(+), 12 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/vdpa/ifcvf/ifcvf_base.h 
>>>>>> b/drivers/vdpa/ifcvf/ifcvf_base.h
>>>>>> index b2eeb16b9c2c..1c04cd256fa7 100644
>>>>>> --- a/drivers/vdpa/ifcvf/ifcvf_base.h
>>>>>> +++ b/drivers/vdpa/ifcvf/ifcvf_base.h
>>>>>> @@ -84,6 +84,7 @@ struct ifcvf_hw {
>>>>>>       u32 notify_off_multiplier;
>>>>>>       u64 req_features;
>>>>>>       u64 hw_features;
>>>>>> +    u32 dev_type;
>>>>>>       struct virtio_pci_common_cfg __iomem *common_cfg;
>>>>>>       void __iomem *net_cfg;
>>>>>>       struct vring_info vring[IFCVF_MAX_QUEUE_PAIRS * 2];
>>>>>> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c 
>>>>>> b/drivers/vdpa/ifcvf/ifcvf_main.c
>>>>>> index 44d7586019da..99b0a6b4c227 100644
>>>>>> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
>>>>>> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
>>>>>> @@ -323,19 +323,9 @@ static u32 ifcvf_vdpa_get_generation(struct 
>>>>>> vdpa_device *vdpa_dev)
>>>>>>     static u32 ifcvf_vdpa_get_device_id(struct vdpa_device 
>>>>>> *vdpa_dev)
>>>>>>   {
>>>>>> -    struct ifcvf_adapter *adapter = vdpa_to_adapter(vdpa_dev);
>>>>>> -    struct pci_dev *pdev = adapter->pdev;
>>>>>> -    u32 ret = -ENODEV;
>>>>>> -
>>>>>> -    if (pdev->device < 0x1000 || pdev->device > 0x107f)
>>>>>> -        return ret;
>>>>>> -
>>>>>> -    if (pdev->device < 0x1040)
>>>>>> -        ret =  pdev->subsystem_device;
>>>>>> -    else
>>>>>> -        ret =  pdev->device-0x1040;
>>>>>> +    struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev);
>>>>>>   -    return ret;
>>>>>> +    return vf->dev_type;
>>>>>>   }
>>>>>>     static u32 ifcvf_vdpa_get_vendor_id(struct vdpa_device 
>>>>>> *vdpa_dev)
>>>>>> @@ -466,6 +456,14 @@ static int ifcvf_probe(struct pci_dev *pdev, 
>>>>>> const struct pci_device_id *id)
>>>>>>       pci_set_drvdata(pdev, adapter);
>>>>>>         vf = &adapter->vf;
>>>>>> +    if (pdev->device < 0x1000 || pdev->device > 0x107f)
>>>>>> +        return -EOPNOTSUPP;
>>>>>> +
>>>>>> +    if (pdev->device < 0x1040)
>>>>>> +        vf->dev_type =  pdev->subsystem_device;
>>>>>> +    else
>>>>>> +        vf->dev_type =  pdev->device - 0x1040;
>>>>>
>>>>>
>>>>> So a question here, is the device a transtional device or modern one?
>>>>>
>>>>> If it's a transitonal one, can it swtich endianess automatically 
>>>>> or not?
>>>>>
>>>>> Thanks
>>>> Hi Jason,
>>>>
>>>> This driver should drive both modern and transitional devices as we 
>>>> discussed before.
>>>> If it's a transitional one, it will act as a modern device by 
>>>> default, legacy mode is a fail-over path.
>>>
>>>
>>> Note that legacy driver use native endian, support legacy driver 
>>> requires the device to know native endian which I'm not sure your 
>>> device can do that.
>>>
>>> Thanks
>> Yes, legacy requires guest native endianess, I think we don't need to 
>> worry about this because our transitional device should work in 
>> modern mode by
>> default(legacy mode is the failover path we will never reach, 
>> get_features will fail if no ACCESS_PLATFORM), we don't support 
>> legacy device in vDPA.
>>
>> Thanks
>
>
> Ok, so I think it's better to add a comment here.
sure, will add a comment in V2

Thanks
>
> Thanks
>
>
>>>
>>>
>>>> For vDPA, it has to support VIRTIO_1 and ACCESS_PLATFORM, so it 
>>>> must in modern mode.
>>>> I think we don't need to worry about endianess for legacy mode.
>>>>
>>>> Thanks
>>>> Zhu Lingshan
>>>>>
>>>>>
>>>>>> +
>>>>>>       vf->base = pcim_iomap_table(pdev);
>>>>>>         adapter->pdev = pdev;
>>>>>
>>>>
>>>
>>
>