Re: [virtio-dev] Re: [PATCH v1] virtio-mmio: Specify wait needed in driver during reset

[Srivatsa Vaddagiri <quic_svaddagi@quicinc.com>]

* Jason Wang <jasowang@redhat.com> [2021-08-18 10:54:37]:

> >I think the option we discussed earlier of a new feature bit seems less
> >intrusive than incrementing MMIO version?
> >
> >https://lists.oasis-open.org/archives/virtio-dev/202107/msg00168.html
> 
> 
> Using features will result some interesting question:
> 
> 1) the drivers usually reset the device before feature negotiation
> 2) it means the driver must mandate this behavior even before feature
> negotiation is done
> 
> We don't have those issue if we increase the version (but it looks more
> intrusive).

Hmm ..are you suggesting that we read the Version register as part of reset code
and do the wait part only for v3 device? Otherwise we have the same issue as
feature bit with version change also. 

Can't the driver do the same with feature register also? Do poll if
WAIT_FOR_RESET_COMPLETION feature bit is set, which can happen before feature
negotiation is complete.

- vatsa

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