Re: [dpdk-dev] [PATCH v5 3/3] PCI: don't use vfio ioctl call to access PIO resource

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 1/26/2021 10:44 AM, Maxime Coquelin wrote:
> 
> 
> On 1/22/21 8:25 AM, 谢华伟(此时此刻） wrote:
>>
>> On 2021/1/21 23:38, Maxime Coquelin wrote:
>>>> Do you mean we apply or abandon patch 3? I am both OK. The first
>>>> priority to me is to enable MMIO bar support.
>>> OK, so yes, I think we should abandon patch 2 and patch 3.
>>> For patch 1, it looks valid to me, but I'll let Ferruh decide.
>>>
>>> For your device, if my understanding is correct, what we need to do is
>>> to support MMIO for legacy devices. Correct?
>> yes.
>>> If so, the change should be in virtio_pci.c. In vtpci_init(), after
>>> modern detection has failed, we should check the the BAR is PIO or MMIO
>>> based on the flag. the result can be saved in struct virtio_pci_dev.
>>>
>>>
>>> We would introduce new wrappers like vtpci_legacy_read,
>>> vtpci_legacy_write that would either call rte_pci_ioport_read,
>>> rte_pci_ioport_read in case of PIO, or rte_read32, rte_write32 in case
>>> of MMIO.
>>
>> There are two choices.
>>
>> 1, apply patch 2.
>>
>>      IO/MMIO port are mapped and accessed using the same API. Kernel is
>> doing in the same way like the following.
>>
>>              io_addr = pci_iomap
>>
>>                  get PIO directly or ioremap
>>
>>              iowrite16/32(val, io_addr + offset)
>>
>> I think applying patch 2 is a correct choice. It is a fix. Driver had
>> better not know if bar is PIO or MMIO.  ioport in ioport_xx API means
>> IO, not PIO.
>>
>> Btw, it only affects virtio PMD,  not that intrusive.
>>
>>   2, virtio specific change to enable MMIO support.
>>
>> Comparing with choice 1, i feels it is not that clean and pretty.
> 
> OK, that makes sense. I am OK with keeping patch 2, but would like
> Ferruh's ACK.
> 

I was waiting for clarification if this can be solved in virtio, which seems 
clarified and decided to go with this patch, I am OK to proceed with patch 1 & 2.

But first patch changes how PIO address get, it changes the Linux interface used 
to get the PIO.
And as far as I can see second patch requires this new interface to be able to 
access the MEM resources.

I have a concern that this interface change may cause issues with various 
distros, kernel versions etc.. And prefer it goes through a full -rc1 validation 
cycle.

Huawei, I am aware the patch is around for a while but to play safe, I suggest 
considering it for early next release, so it can be tested enough, instead of 
getting if for -rc2/3 in this release.

Thanks,
ferruh


> Could you please post v6?
> 
> Thanks,
> Maxime
> 
>>>
>>> It is not too late for this release, as the change will not be that
>>> intrusive. But if you prepare such patch, please base it on top of my
>>> virtio rework series; To make it easier to you, I added it to the dpdk-
>>> next-virtio tree:
>>> https://git.dpdk.org/next/dpdk-next-virtio/log/?h=virtio_pmd_rework_v2
>>>
>>> Thanks,
>>> Maxime
>>>
>>
>