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Re: [Qemu-devel] [RFC v2 1/2] docs: vhost-user: add in-band kick/call me
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [RFC v2 1/2] docs: vhost-user: add in-band kick/call messages |
Date: |
Thu, 12 Sep 2019 09:09:32 +0100 |
User-agent: |
Mutt/1.12.1 (2019-06-15) |
* Johannes Berg (address@hidden) wrote:
> 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/
Ah OK.
You're actually using the same trick of using
REPLY_ACK/need_reply to make it synchronous that set_mem_table does;
that makes sense - but then new calls are getting it to actually process
some data/commands on the ring itself?
Dave
> Thanks,
> johannes
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
Re: [Qemu-devel] [RFC v2 1/2] docs: vhost-user: add in-band kick/call messages, Dr. David Alan Gilbert, 2019/09/11
Re: [Qemu-devel] [RFC v2 0/2] vhost-user: in-band notifications, no-reply, 2019/09/11