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Subject: Re: [PATCH 1/3] vDPA/ifcvf: deduce VIRTIO device ID when probe
To:     Jason Wang <jasowang@redhat.com>,
        Zhu Lingshan <lingshan.zhu@intel.com>, mst@redhat.com,
        lulu@redhat.com, leonro@nvidia.com
Cc:     virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20210414091832.5132-1-lingshan.zhu@intel.com>
 <20210414091832.5132-2-lingshan.zhu@intel.com>
 <85483ff1-cf98-ad05-0c53-74caa2464459@redhat.com>
 <ccf7001b-27f0-27ea-40d2-52ca3cc2386b@linux.intel.com>
 <ffd2861d-2395-de51-a227-f1ef33f74322@redhat.com>
From:   Zhu Lingshan <lingshan.zhu@linux.intel.com>
Message-ID: <92ef6264-4462-cbd4-5db8-6ce6b68762e0@linux.intel.com>
Date:   Thu, 15 Apr 2021 14:36:15 +0800
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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@intel.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
>
>
>> 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;
>>>
>>
>