From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51082) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cS5HB-0004Kg-GC for qemu-devel@nongnu.org; Fri, 13 Jan 2017 12:04:31 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cS5H8-0008Mh-Aa for qemu-devel@nongnu.org; Fri, 13 Jan 2017 12:04:29 -0500 Received: from mx1.redhat.com ([209.132.183.28]:49674) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cS5H8-0008LZ-1W for qemu-devel@nongnu.org; Fri, 13 Jan 2017 12:04:26 -0500 Date: Fri, 13 Jan 2017 19:04:23 +0200 From: "Michael S. Tsirkin" Message-ID: <20170113190029-mutt-send-email-mst@kernel.org> References: <1484270047-24579-1-git-send-email-felipe@nutanix.com> <1587720065.2308546.1484319819288.JavaMail.zimbra@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH] libvhost-user: Start VQs on SET_VRING_CALL List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Felipe Franciosi Cc: =?iso-8859-1?Q?Marc-Andr=E9?= Lureau , Paolo Bonzini , Stefan Hajnoczi , Marc-Andre Lureau , qemu-devel , Peter Maydell , Eric Blake , Markus Armbruster , "Daniel P. Berrange" On Fri, Jan 13, 2017 at 03:09:46PM +0000, Felipe Franciosi wrote: > Hi Marc-Andre, >=20 > > On 13 Jan 2017, at 07:03, Marc-Andr=E9 Lureau wr= ote: > >=20 > > Hi > >=20 > > ----- Original Message ----- > >> Currently, VQs are started as soon as a SET_VRING_KICK is received. = That > >> is too early in the VQ setup process, as the backend might not yet h= ave > >=20 > > I think we may want to reconsider queue_set_started(), move it elsewh= ere, since kick/call fds aren't mandatory to process the rings. >=20 > Hmm. The fds aren't mandatory, but I imagine in that case we should sti= ll receive SET_VRING_KICK/CALL messages without an fd (ie. with the VHOST= _MSG_VQ_NOFD_MASK flag set). Wouldn't that be the case? Please look at docs/specs/vhost-user.txt, Starting and stopping rings The spec says: Client must start ring upon receiving a kick (that is, detecting that file descriptor is readable) on the descriptor specified by VHOST_USER_SET_VRING_KICK, and stop ring upon receiving VHOST_USER_GET_VRING_BASE. > >=20 > >> a callfd to notify in case it received a kick and fully processed th= e > >> request/command. This patch only starts a VQ when a SET_VRING_CALL i= s > >> received. > >=20 > > I don't like that much, as soon as the kick fd is received, it should= start polling it imho. callfd is optional, it may have one and not the o= ther. >=20 > So the question is whether we should be receiving a SET_VRING_CALL anyw= ay or not, regardless of an fd being sent. (I think we do, but I haven't = done extensive testing with other device types.) I would say not, only KICK is mandatory and that is also not enough to process ring. You must wait for it to be readable. > >=20 > > Perhaps it's best for now to delay the callfd notification with a fla= g until it is received? >=20 > The other idea is to always kick when we receive the callfd. I remember= discussing that alternative with you before libvhost-user went in. The p= rotocol says both the driver and the backend must handle spurious kicks. = This approach also fixes the bug. >=20 > I'm happy with whatever alternative you want, as long it makes libvhost= -user usable for storage devices. >=20 > Thanks, > Felipe >=20 >=20 > >=20 > >=20 > >> Signed-off-by: Felipe Franciosi > >> --- > >> contrib/libvhost-user/libvhost-user.c | 26 +++++++++++++------------= - > >> 1 file changed, 13 insertions(+), 13 deletions(-) > >>=20 > >> diff --git a/contrib/libvhost-user/libvhost-user.c > >> b/contrib/libvhost-user/libvhost-user.c > >> index af4faad..a46ef90 100644 > >> --- a/contrib/libvhost-user/libvhost-user.c > >> +++ b/contrib/libvhost-user/libvhost-user.c > >> @@ -607,19 +607,6 @@ vu_set_vring_kick_exec(VuDev *dev, VhostUserMsg= *vmsg) > >> DPRINT("Got kick_fd: %d for vq: %d\n", vmsg->fds[0], index); > >> } > >>=20 > >> - dev->vq[index].started =3D true; > >> - if (dev->iface->queue_set_started) { > >> - dev->iface->queue_set_started(dev, index, true); > >> - } > >> - > >> - if (dev->vq[index].kick_fd !=3D -1 && dev->vq[index].handler) { > >> - dev->set_watch(dev, dev->vq[index].kick_fd, VU_WATCH_IN, > >> - vu_kick_cb, (void *)(long)index); > >> - > >> - DPRINT("Waiting for kicks on fd: %d for vq: %d\n", > >> - dev->vq[index].kick_fd, index); > >> - } > >> - > >> return false; > >> } > >>=20 > >> @@ -661,6 +648,19 @@ vu_set_vring_call_exec(VuDev *dev, VhostUserMsg= *vmsg) > >>=20 > >> DPRINT("Got call_fd: %d for vq: %d\n", vmsg->fds[0], index); > >>=20 > >> + dev->vq[index].started =3D true; > >> + if (dev->iface->queue_set_started) { > >> + dev->iface->queue_set_started(dev, index, true); > >> + } > >> + > >> + if (dev->vq[index].kick_fd !=3D -1 && dev->vq[index].handler) { > >> + dev->set_watch(dev, dev->vq[index].kick_fd, VU_WATCH_IN, > >> + vu_kick_cb, (void *)(long)index); > >> + > >> + DPRINT("Waiting for kicks on fd: %d for vq: %d\n", > >> + dev->vq[index].kick_fd, index); > >> + } > >> + > >> return false; > >> } > >>=20 > >> -- > >> 1.9.4 > >>=20 > >>=20 >=20