netdev - Re: [PATCH 1/2] vDPA/ifcvf: record virtio notify base

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Date:   Wed, 28 Apr 2021 18:18:35 +0800
From:   "Zhu, Lingshan" <lingshan.zhu@...el.com>
To:     Jason Wang <jasowang@...hat.com>, mst@...hat.com
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] vDPA/ifcvf: record virtio notify base



On 4/28/2021 6:09 PM, Jason Wang wrote:
>
> 在 2021/4/28 下午6:00, Zhu, Lingshan 写道:
>>
>>
>> On 4/28/2021 4:39 PM, Jason Wang wrote:
>>>
>>> 在 2021/4/28 下午4:21, Zhu Lingshan 写道:
>>>> This commit records virtio notify base addr to implemente
>>>> doorbell mapping feature
>>>>
>>>> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
>>>> ---
>>>>   drivers/vdpa/ifcvf/ifcvf_base.c | 1 +
>>>>   drivers/vdpa/ifcvf/ifcvf_base.h | 1 +
>>>>   2 files changed, 2 insertions(+)
>>>>
>>>> diff --git a/drivers/vdpa/ifcvf/ifcvf_base.c 
>>>> b/drivers/vdpa/ifcvf/ifcvf_base.c
>>>> index 1a661ab45af5..cc61a5bfc5b1 100644
>>>> --- a/drivers/vdpa/ifcvf/ifcvf_base.c
>>>> +++ b/drivers/vdpa/ifcvf/ifcvf_base.c
>>>> @@ -133,6 +133,7 @@ int ifcvf_init_hw(struct ifcvf_hw *hw, struct 
>>>> pci_dev *pdev)
>>>> &hw->notify_off_multiplier);
>>>>               hw->notify_bar = cap.bar;
>>>>               hw->notify_base = get_cap_addr(hw, &cap);
>>>> +            hw->notify_pa = pci_resource_start(pdev, cap.bar) + 
>>>> cap.offset;
>>>
>>>
>>> To be more generic and avoid future changes, let's use the math 
>>> defined in the virtio spec.
>>>
>>> You may refer how it is implemented in virtio_pci vdpa driver[1].
>> Are you suggesting every vq keep its own notify_pa? In this case, we 
>> still need to record notify_pa in hw when init_hw, then initialize 
>> vq->notify_pa accrediting to hw->notify_pa.
>
>
> I meant you need to follow how virtio spec did to calculate the 
> doorbell address per vq:
>
>         cap.offset + queue_notify_off * notify_off_multiplier
>
> Obviously, you ignore queue_notify_off and notify_off_multiplier here. 
> This may bring troubles for the existing device IFCVF and future devices.
>
> If I understand correctly, this device can be probed by virtio-pci 
> driver which use the above math. There's no reason for using ad-hoc hack.
sure, when talking about initialize vq->notify_pa, I mean calculate with 
with notify_base and multiplier, V2 will include this.

Thanks,
Zhu Lingshan
>
> Thanks
>
>
>>
>> Thanks
>> Zhu Lingshan
>>>
>>> Thanks
>>>
>>> [1] 
>>> https://lore.kernel.org/virtualization/20210415073147.19331-5-jasowang@redhat.com/T/
>>>
>>>
>>>> IFCVF_DBG(pdev, "hw->notify_base = %p\n",
>>>>                     hw->notify_base);
>>>>               break;
>>>> diff --git a/drivers/vdpa/ifcvf/ifcvf_base.h 
>>>> b/drivers/vdpa/ifcvf/ifcvf_base.h
>>>> index 0111bfdeb342..bcca7c1669dd 100644
>>>> --- a/drivers/vdpa/ifcvf/ifcvf_base.h
>>>> +++ b/drivers/vdpa/ifcvf/ifcvf_base.h
>>>> @@ -98,6 +98,7 @@ struct ifcvf_hw {
>>>>       char config_msix_name[256];
>>>>       struct vdpa_callback config_cb;
>>>>       unsigned int config_irq;
>>>> +    phys_addr_t  notify_pa;
>>>>   };
>>>>     struct ifcvf_adapter {
>>>
>>
>