From: "Michael S. Tsirkin" <mst@redhat.com>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [RFC] libvhost-user: implement VHOST_USER_PROTOCOL_F_KICK_CALL_MSGS
Date: Mon, 9 Sep 2019 10:59:26 -0400 [thread overview]
Message-ID: <20190909105057-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <d2e750aaec396bd0aa7ea8c05ef5705567d16595.camel@sipsolutions.net>
On Mon, Sep 09, 2019 at 03:50:48PM +0200, Johannes Berg wrote:
> On Mon, 2019-09-09 at 09:48 -0400, Michael S. Tsirkin wrote:
>
> > > I suppose we could fail a later command that already needs a reply
> > > without REPLY_ACK, but that seems difficult to debug?
> >
> > Next command is GET_FEATURES. Return an error response from that
> > and device init will fail.
>
> Hmm, what's an error here though? You can only return a value, no?
Either returning id that does not match GET_FEATURES or
returning size != 8 bytes will work.
Using 0 size payload has precedent in VHOST_USER_GET_CONFIG:
vhost-user slave uses zero length of
payload to indicate an error to vhost-user master.
It's annoying that we don't get an error indicator in that case though.
Worth returning e.g. a 4 byte code?
And let's generalize for all other messages with response?
> > > Anyway, if you feel that we should have this as some sort of safeguard I
> > > can try to do that; to me it feels rather pointless as libvhost-user is
> > > more of a sample implementation than anything else.
> >
> > Exactly for this reason :)
>
> :)
>
> > > Unless you also wanted to write into the spec that F_KICK_CALL_MSGS
> > > absolutely *requires* F_REPLY_ACK,
> >
> > yep
>
> Sure, I'm fine with that.
>
> > We can document how to behave in case of inconsistent protocol features,
> > yes.
>
> OK.
>
> johannes
next prev parent reply other threads:[~2019-09-09 15:00 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-02 12:12 [Qemu-devel] [RFC] vhost-user simulation extension Johannes Berg
2019-09-02 12:12 ` [Qemu-devel] [RFC] docs: vhost-user: add in-band kick/call messages Johannes Berg
2019-09-05 20:28 ` Johannes Berg
2019-09-09 16:00 ` Stefan Hajnoczi
2019-09-09 17:34 ` Johannes Berg
2019-09-10 15:03 ` Stefan Hajnoczi
2019-09-10 15:14 ` Johannes Berg
2019-09-10 15:33 ` Michael S. Tsirkin
2019-09-10 15:34 ` Johannes Berg
2019-09-11 6:56 ` Stefan Hajnoczi
2019-09-11 7:35 ` Stefan Hajnoczi
2019-09-11 8:26 ` Johannes Berg
2019-09-11 15:17 ` Stefan Hajnoczi
2019-09-11 15:31 ` Stefan Hajnoczi
2019-09-11 15:36 ` Johannes Berg
2019-09-11 15:38 ` Johannes Berg
2019-09-12 12:22 ` Stefan Hajnoczi
2019-09-12 20:37 ` Johannes Berg
2019-09-06 12:13 ` [Qemu-devel] [RFC] libvhost-user: implement VHOST_USER_PROTOCOL_F_KICK_CALL_MSGS Johannes Berg
2019-09-06 14:22 ` Michael S. Tsirkin
2019-09-06 14:48 ` Johannes Berg
2019-09-06 15:12 ` Michael S. Tsirkin
2019-09-06 15:32 ` Johannes Berg
2019-09-08 13:13 ` Michael S. Tsirkin
2019-09-09 11:35 ` Johannes Berg
2019-09-09 12:41 ` Michael S. Tsirkin
2019-09-09 13:05 ` Johannes Berg
2019-09-09 13:48 ` Michael S. Tsirkin
2019-09-09 13:50 ` Johannes Berg
2019-09-09 14:59 ` Michael S. Tsirkin [this message]
2019-09-09 15:26 ` Johannes Berg
2019-09-09 15:34 ` Johannes Berg
2019-09-09 15:45 ` Michael S. Tsirkin
2019-09-09 15:47 ` Johannes Berg
2019-09-10 15:52 ` Johannes Berg
2019-09-11 9:16 ` Michael S. Tsirkin
2019-09-11 9:20 ` Johannes Berg
2019-09-11 9:54 ` Michael S. Tsirkin
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