Re: [Qemu-devel] [RFC v2 1/2] docs: vhost-user: add in-band kick/call messages

[Johannes Berg]

On Wed, 2019-09-11 at 20:15 +0100, Dr. David Alan Gilbert wrote:

> > Extend the protocol slightly, so that a message can be used for kick
> > and call instead, if VHOST_USER_PROTOCOL_F_IN_BAND_NOTIFICATIONS is
> > negotiated. This in itself doesn't guarantee synchronisation, but both
> > sides can also negotiate VHOST_USER_PROTOCOL_F_REPLY_ACK and thus get
> > a reply to this message by setting the need_reply flag, and ensure
> > synchronisation this way.
> 
> I'm confused; if you've already got REPLY_ACK, why do we need anything
> else?  We already require the reply on set_mem_table as part of
> postcopy.

Hmm? How's this related to set_mem_table?

For simulation purposes, I need the kick and call (and error perhaps
though it's not really used by anyone now it seems) to be synchronous
messages instead of asynchronous event FD pushes.

But I think enough words have been expended on explaining it already, if
I may kindly ask you to read the discussions with Stefan and Michael
here:

https://lore.kernel.org/qemu-devel/address@hidden/

Thanks,
johannes