Re: [PATCH V2 2/2] virtio: introduce STOP status bit

[Cornelia Huck <cohuck@redhat.com>]

On Wed, Jul 07 2021, Jason Wang <jasowang@redhat.com> wrote:

> å 2021/7/6 äå10:27, Cornelia Huck åé:
>> On Tue, Jul 06 2021, Jason Wang <jasowang@redhat.com> wrote:
>>
>>> å 2021/7/6 äå8:50, Cornelia Huck åé:
>>>> On Tue, Jul 06 2021, Jason Wang <jasowang@redhat.com> wrote:
>>>>> +If VIRTIO_F_STOP has been negotiated, to stop a device, after setting
>>>>> +STOP, the driver MUST re-read the device status to ensure the STOP bit
>>>>> +is set to synchronize with the device.
>>>> Is this more that the driver needs to re-read the status until STOP is
>>>> set to make sure that the stop process has finished?
>>>
>>> Yes.
>>>
>>>
>>>>    If the device has
>>>> offered the feature and the driver accepted it, I'd assume that the
>>>> device will eventually finish with the procedure, or sets NEEDS_RESET if
>>>> something goes wrong?
>>>
>>> As stated below, the device must either:
>>>
>>> 1) finish all pending requests
>>>
>>> or
>>>
>>> 2) provide a device specific way for the driver to save and restore
>>> pending requests
>>>
>>> before setting STOP.
>>>
>>> Otherwise the device can't offer this feature.
>>>
>>> Using NEEDS_RESET seems more complicated than this.
>> Hm, what happens on an internal error?
>
>
> A question, can reset fail? If yes, do we need to define how to proceed 
> in the driver side?
>
> If not, I don't need the reason we need to deal with that in the STOP.

When you put it that way, it makes sense. Let's just keep it simple,
then.