From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50569) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZDXzr-0002hK-UV for qemu-devel@nongnu.org; Fri, 10 Jul 2015 09:05:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZDXzm-0006DE-Ud for qemu-devel@nongnu.org; Fri, 10 Jul 2015 09:05:43 -0400 Received: from mail-wi0-x233.google.com ([2a00:1450:400c:c05::233]:34809) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZDXzm-0006Cf-GV for qemu-devel@nongnu.org; Fri, 10 Jul 2015 09:05:38 -0400 Received: by wifm2 with SMTP id m2so45974056wif.1 for ; Fri, 10 Jul 2015 06:05:37 -0700 (PDT) Sender: Paolo Bonzini References: <1435310564-9418-1-git-send-email-thibaut.collet@6wind.com> <1435310564-9418-2-git-send-email-thibaut.collet@6wind.com> From: Paolo Bonzini Message-ID: <559FC31E.10600@redhat.com> Date: Fri, 10 Jul 2015 15:05:34 +0200 MIME-Version: 1.0 In-Reply-To: <1435310564-9418-2-git-send-email-thibaut.collet@6wind.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v4 1/1] vhost user: add support of live migration List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Thibaut Collet , mst@redhat.com, stefanha@redhat.com, jasowang@redhat.com, qemu-devel@nongnu.org On 26/06/2015 11:22, Thibaut Collet wrote: > Some vhost client/backend are able to support live migration. > To provide this service the following features must be added: > 1. Add the VIRTIO_NET_F_GUEST_ANNOUNCE capability to vhost-net when netdev > backend is vhost-user. > 2. Provide a nop receive callback to vhost-user. This callback is for RARP > packets automatically send by qemu_announce_self after a migration. > These packets are useless for vhost user and just discarded. When a packet is received by vhost-user, the vhost-user writes the packet in guest memory. QEMU must then copy that page of guest memory from source to destination; it uses a dirty bitmap for this purpose. How does vhost-user do this? I can see this patch providing enough support for *non*live migration. However, it cannot be enough for live migration unless I'm missing something obvious. Paolo > Signed-off-by: Thibaut Collet > --- > hw/net/vhost_net.c | 2 ++ > net/vhost-user.c | 21 +++++++++++++++++++-- > 2 files changed, 21 insertions(+), 2 deletions(-) > > diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c > index 9bd360b..668c422 100644 > --- a/hw/net/vhost_net.c > +++ b/hw/net/vhost_net.c > @@ -85,6 +85,8 @@ static const int user_feature_bits[] = { > VIRTIO_NET_F_CTRL_MAC_ADDR, > VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, > > + VIRTIO_NET_F_GUEST_ANNOUNCE, > + > VIRTIO_NET_F_MQ, > > VHOST_INVALID_FEATURE_BIT > diff --git a/net/vhost-user.c b/net/vhost-user.c > index b51bc04..20778a1 100644 > --- a/net/vhost-user.c > +++ b/net/vhost-user.c > @@ -65,6 +65,24 @@ static void vhost_user_stop(VhostUserState *s) > s->vhost_net = 0; > } > > +static ssize_t vhost_user_receive(NetClientState *nc, const uint8_t *buf, > + size_t size) > +{ > + /* A live migration is done. Display an error if the packet is not a RARP. > + * RARP are just discarded: guest is already notified of live migration > + * by the virtio-net NIC or by the vhost-user backend */ > + if (size != 60) { > + static int display_trace = 1; > + > + if (display_trace) { > + fprintf(stderr,"Vhost user receives unexpected packets\n"); > + fflush(stderr); > + display_trace = 0; > + } > + } > + return size; > +} > + > static void vhost_user_cleanup(NetClientState *nc) > { > VhostUserState *s = DO_UPCAST(VhostUserState, nc, nc); > @@ -90,6 +108,7 @@ static bool vhost_user_has_ufo(NetClientState *nc) > static NetClientInfo net_vhost_user_info = { > .type = NET_CLIENT_OPTIONS_KIND_VHOST_USER, > .size = sizeof(VhostUserState), > + .receive = vhost_user_receive, > .cleanup = vhost_user_cleanup, > .has_vnet_hdr = vhost_user_has_vnet_hdr, > .has_ufo = vhost_user_has_ufo, > @@ -146,8 +165,6 @@ static int net_vhost_user_init(NetClientState *peer, const char *device, > > s = DO_UPCAST(VhostUserState, nc, nc); > > - /* We don't provide a receive callback */ > - s->nc.receive_disabled = 1; > s->chr = chr; > s->nc.queue_index = i; > >