Re: [virtio-dev] Re: [PATCH V2 2/2] virtio-pci: add PASID configuration extended capability

[Jason Wang <jasowang@redhat.com>]

在 2022/1/13 下午11:17, Michael S. Tsirkin 写道:
> On Thu, Jan 13, 2022 at 02:53:36PM +0000, Stefan Hajnoczi wrote:
>> On Thu, Jan 13, 2022 at 05:45:11AM -0500, Michael S. Tsirkin wrote:
>>> On Thu, Jan 13, 2022 at 10:32:11AM +0000, Stefan Hajnoczi wrote:
>>>>> So my understanding is that instead of delaying the response to read
>>>>> it's better to simply present the previous PASID value if there're any
>>>>> pending transactions of previous PASID value. The driver can then
>>>>> choose to poll or using timers etc.
>>> Don't we limit these changes to before DRIVER_OK?
>>> If we do then no previous transactions can exist.
>> Not sure if that's possible for the vDPA virtqueue assignment use case
>> where one large VIRTIO device provides virtqueues for many smaller vDPA
>> devices?


That could be the case but usually a smaller vDPA device requires a 
bunch of hardware resources more than just virtqueues.

Another example is assign a queue directly to userspace with PASID for SVA.


>>
>> Stefan
> Then I guess queue must be stopped?


Yes, since we have virtqueue reset, I can limit the assigning before 
DRIVER_OK or queue(s) are reset. Does this work?

Thanks


>


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