Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH V3 1/6] vDPA/ifcvf: get_vendor_id returns a device
 specific vendor id
To:     Zhu Lingshan <lingshan.zhu@linux.intel.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: <20210310090052.4762-1-lingshan.zhu@intel.com>
 <20210310090052.4762-2-lingshan.zhu@intel.com>
 <ff5fc8f9-f886-bd2a-60cc-771c628c6c4b@redhat.com>
 <5f2d915f-e1b0-c9eb-9fc8-4b64f5d8cd0f@linux.intel.com>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <05e3fbc9-be49-a208-19a4-85f891323312@redhat.com>
Date:   Thu, 11 Mar 2021 14:13:20 +0800
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.16; rv:78.0)
 Gecko/20100101 Thunderbird/78.8.0
MIME-Version: 1.0
In-Reply-To: <5f2d915f-e1b0-c9eb-9fc8-4b64f5d8cd0f@linux.intel.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-GB
Precedence: bulk


On 2021/3/11 12:21 下午, Zhu Lingshan wrote:
>
>
> On 3/11/2021 11:23 AM, Jason Wang wrote:
>>
>> On 2021/3/10 5:00 下午, Zhu Lingshan wrote:
>>> In this commit, ifcvf_get_vendor_id() will return
>>> a device specific vendor id of the probed pci device
>>> than a hard code.
>>>
>>> Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
>>> ---
>>>   drivers/vdpa/ifcvf/ifcvf_main.c | 5 ++++-
>>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c 
>>> b/drivers/vdpa/ifcvf/ifcvf_main.c
>>> index fa1af301cf55..e501ee07de17 100644
>>> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
>>> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
>>> @@ -324,7 +324,10 @@ static u32 ifcvf_vdpa_get_device_id(struct 
>>> vdpa_device *vdpa_dev)
>>>     static u32 ifcvf_vdpa_get_vendor_id(struct vdpa_device *vdpa_dev)
>>>   {
>>> -    return IFCVF_SUBSYS_VENDOR_ID;
>>> +    struct ifcvf_adapter *adapter = vdpa_to_adapter(vdpa_dev);
>>> +    struct pci_dev *pdev = adapter->pdev;
>>> +
>>> +    return pdev->subsystem_vendor;
>>>   }
>>
>>
>> While at this, I wonder if we can do something similar in 
>> get_device_id() if it could be simple deduced from some simple math 
>> from the pci device id?
>>
>> Thanks
> Hi Jason,
>
> IMHO, this implementation is just some memory read ops, I think other 
> implementations may not save many cpu cycles, an if cost at least 
> three cpu cycles.
>
> Thanks!


Well, I meant whehter you can deduce virtio device id from 
pdev->subsystem_device.

Thanks


>>
>>
>>>     static u32 ifcvf_vdpa_get_vq_align(struct vdpa_device *vdpa_dev)
>>
>