Re: [virtio] Re: [PATCH] ccw: clarify device reset

[Halil Pasic <pasic@linux.ibm.com>]

On Thu, 21 Oct 2021 18:23:51 +0200
Cornelia Huck <cohuck@redhat.com> wrote:

> >
> > Halil, do you know if this has moved somewhere else? If yes, we need to
> > update the link.  
> 

I can't remember they told me about moving it ;)

I've found this one, and my guess is it works form the outside:

https://www.ibm.com/resources/publications/OutputPubsDetails?PubID=SA22720401


> Also, do you have any feedback on this patch?

I didn't see anything obviously wrong.

"""
+The device signals completion of the reset operation by making the subchannel
+status pending to indicate successful completion of the channel command.
"""

may be little ambiguous. IMHO the point we should make is that the
successful completion of the virtio reset happens before the
successful completion of the ccw that requested the operation. "Status
pending" is a little broad. We could get status pending with something
like alert status, at least in theory. And if somebody silly would put
the reset command with more commands following it in a channel program,
we would not have to wait for the channel to complete and to see a status pending
indicated at the subchannel.

Another interesting question for the reset is system boundary. I.e. what
exactly is reset.  Some publications describe possible electric
signaling interfaces, and I doubt this kind of a reset would be a
complete reset of the device from that perspective. But that  question is
not what this patch is about. It just came to my mind.

Sorry guys I'm already with one foot in vacation. This is the extent to
which I can contribute right now.

Regards,
Halil