From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60766) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wv2hD-0007FF-E4 for qemu-devel@nongnu.org; Thu, 12 Jun 2014 06:57:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Wv2h8-00079y-BT for qemu-devel@nongnu.org; Thu, 12 Jun 2014 06:57:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:6266) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wv2h8-00079N-2m for qemu-devel@nongnu.org; Thu, 12 Jun 2014 06:57:22 -0400 Date: Thu, 12 Jun 2014 13:57:44 +0300 From: "Michael S. Tsirkin" Message-ID: <20140612105744.GH22230@redhat.com> References: <20140529111253.4ff55199@bahia.local> <538708FA.4070309@redhat.com> <20140612094351.6295fd38@bahia.local> <53996B0E.4040808@redhat.com> <20140612110601.3fe5626e@bahia.local> <539970B3.3040304@redhat.com> <20140612093712.GA22565@redhat.com> <5399755E.10902@redhat.com> <53997638.6020403@suse.de> <20140612121440.6ce62e77@bahia.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140612121440.6ce62e77@bahia.local> Subject: Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Greg Kurz Cc: Kevin Wolf , Fam Zheng , Anthony Liguori , Juan Quintela , Alexander Graf , qemu-devel@nongnu.org, Stefan Hajnoczi , Amit Shah , Paolo Bonzini , Andreas =?iso-8859-1?Q?F=E4rber?= On Thu, Jun 12, 2014 at 12:14:40PM +0200, Greg Kurz wrote: > On Thu, 12 Jun 2014 11:43:20 +0200 > Alexander Graf wrote: > > > > > On 12.06.14 11:39, Paolo Bonzini wrote: > > > Il 12/06/2014 11:37, Michael S. Tsirkin ha scritto: > > >> Maybe just drop unnecessary stuff for new machine types? > > >> Then we won't need hacks to migrate it. > > > > > > For any machine type it's trivial to migrate it. All machine types > > > including old ones can disregard the migrated values. > > > > How about a patch like this before the actual LE awareness ones? With > > this we should make virtio-serial config space completely independent of > > live migration. > > > > Also since QEMU versions that do read these swapped values during > > migration are not bi-endian aware, we can never get into a case where a > > cross-endian save needs to be considered ;). > > > > > > Alex > > > > > > diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c > > index 2b647b6..73cb9b7 100644 > > --- a/hw/char/virtio-serial-bus.c > > +++ b/hw/char/virtio-serial-bus.c > > @@ -670,6 +670,7 @@ static int virtio_serial_load(QEMUFile *f, void > > *opaque, int version_id) > > uint32_t max_nr_ports, nr_active_ports, ports_map; > > unsigned int i; > > int ret; > > + uint32_t tmp; > > > > if (version_id > 3) { > > return -EINVAL; > > @@ -685,17 +686,12 @@ static int virtio_serial_load(QEMUFile *f, void > > *opaque, int version_id) > > return 0; > > } > > > > - /* The config space */ > > - qemu_get_be16s(f, &s->config.cols); > > - qemu_get_be16s(f, &s->config.rows); > > - > > - qemu_get_be32s(f, &max_nr_ports); > > - tswap32s(&max_nr_ports); > > - if (max_nr_ports > tswap32(s->config.max_nr_ports)) { > > - /* Source could have had more ports than us. Fail migration. */ > > - return -EINVAL; > > - } > > + /* Unused */ > > + qemu_get_be16s(f, &tmp); > > + qemu_get_be16s(f, &tmp); > > + qemu_get_be32s(f, &tmp); > > > > + max_nr_ports = tswap32(s->config.max_nr_ports); > > for (i = 0; i < (max_nr_ports + 31) / 32; i++) { > > qemu_get_be32s(f, &ports_map); > > > > > > For the moment, we have 0 < max_nr_ports < 32 so the source > machine only stores a single 32 bit value... If this limit > gets raised, we can end up sending more than that... and > only the source machine max_nr_ports value can give the > information... I don't think we need to worry. We won't be able to change max_nr_ports in compat machine types. > -- > Gregory Kurz kurzgreg@fr.ibm.com > gkurz@linux.vnet.ibm.com > Software Engineer @ IBM/Meiosys http://www.ibm.com > Tel +33 (0)562 165 496 > > "Anarchy is about taking complete responsibility for yourself." > Alan Moore.