[virtio-dev] Re: [virtio-comment] Re: [virtio-dev] Re: [PATCH v3 0/3] transport-pci: Introduce legacy registers access using AQ

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, Jun 11, 2023 at 02:08:07AM +0000, Parav Pandit wrote:
> 
> 
> > From: Michael S. Tsirkin <mst@redhat.com>
> > Sent: Saturday, June 10, 2023 8:27 PM
> > 
> > Interesting this actually violates a spec recommendation:
> > 
> > 	If a device has successfully negotiated a set of features
> > 	at least once (by accepting the FEATURES_OK \field{device
> > 	status} bit during device initialization), then it SHOULD
> > 	NOT fail re-negotiation of the same set of features after
> > 	a device or system reset.  Failure to do so would interfere
> > 	with resuming from suspend and error recovery.
> >
> This is how we have seen mlx5 device and it has evolved now to break free such limitation.

It's not conformant to that statement then :( It's a SHOULD which means
if you know exactly what you are doing, there could be exceptions.
In this case it's a SHOULD because it was added after 1.0 and
we did not find a way to negotiate this requirement since it's the feature
negotiation itself.


-- 
MST


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