From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: qemu-devel@nongnu.org, "Michael S . Tsirkin" <mst@redhat.com>
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 [thread overview]
Message-ID: <20190912080932.GA2722@work-vm> (raw)
In-Reply-To: <24d6940040c4f846eaba2154979fd6658b665c98.camel@sipsolutions.net>
* Johannes Berg (johannes@sipsolutions.net) 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/20190902121233.13382-1-johannes@sipsolutions.net/
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 / dgilbert@redhat.com / Manchester, UK
next prev parent reply other threads:[~2019-09-12 8:10 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-11 13:45 [Qemu-devel] [RFC v2 0/2] vhost-user: in-band notifications Johannes Berg
2019-09-11 13:45 ` [Qemu-devel] [RFC v2 1/2] docs: vhost-user: add in-band kick/call messages Johannes Berg
2019-09-11 14:07 ` Michael S. Tsirkin
2019-09-11 15:09 ` Johannes Berg
2019-09-16 11:40 ` Johannes Berg
2019-09-16 15:30 ` Michael S. Tsirkin
2019-09-17 12:01 ` Johannes Berg
2019-09-11 19:15 ` Dr. David Alan Gilbert
2019-09-11 19:18 ` Johannes Berg
2019-09-12 8:09 ` Dr. David Alan Gilbert [this message]
2019-09-12 8:13 ` Johannes Berg
2019-09-11 13:45 ` [Qemu-devel] [RFC v2 2/2] libvhost-user: implement in-band notifications Johannes Berg
2019-09-11 15:01 ` [Qemu-devel] [RFC v2 0/2] vhost-user: " no-reply
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