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[100.0.197.103]) by smtp.gmail.com with ESMTPSA id d23sm3007463qta.26.2019.05.30.12.21.25 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Thu, 30 May 2019 12:21:26 -0700 (PDT) Date: Thu, 30 May 2019 15:21:24 -0400 From: "Michael S. Tsirkin" To: "Dr. David Alan Gilbert" Message-ID: <20190530152104-mutt-send-email-mst@kernel.org> References: <20190517125820.2885-1-jfreimann@redhat.com> <20190517125820.2885-4-jfreimann@redhat.com> <20190521094504.GB2915@work-vm> <20190530145645.tjwkgi4hae5yblsi@jenstp.localdomain> <20190530134631-mutt-send-email-mst@kernel.org> <20190530180022.GB2864@work-vm> <20190530140419-mutt-send-email-mst@kernel.org> <20190530190822.GL2823@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190530190822.GL2823@work-vm> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.85.160.193 Subject: Re: [Qemu-devel] [PATCH 3/4] net/virtio: add failover support X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: pkrempa@redhat.com, berrange@redhat.com, ehabkost@redhat.com, aadam@redhat.com, qemu-devel@nongnu.org, laine@redhat.com, Jens Freimann , ailan@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, May 30, 2019 at 08:08:23PM +0100, Dr. David Alan Gilbert wrote: > * Michael S. Tsirkin (mst@redhat.com) wrote: > > On Thu, May 30, 2019 at 07:00:23PM +0100, Dr. David Alan Gilbert wrote: > > > * Michael S. Tsirkin (mst@redhat.com) wrote: > > > > On Thu, May 30, 2019 at 04:56:45PM +0200, Jens Freimann wrote: > > > > > Hi David, > > > > > > > > > > sorry for the delayed reply. > > > > > > > > > > On Tue, May 28, 2019 at 11:04:15AM -0400, Michael S. Tsirkin wrote: > > > > > > On Tue, May 21, 2019 at 10:45:05AM +0100, Dr. David Alan Gilbert wrote: > > > > > > > * Jens Freimann (jfreimann@redhat.com) wrote: > > > > > > > > +static void virtio_net_primary_plug_timer(void *opaque); > > > > > > > > + > > > > > > > > static void virtio_net_set_link_status(NetClientState *nc) > > > > > > > > { > > > > > > > > VirtIONet *n = qemu_get_nic_opaque(nc); > > > > > > > > @@ -786,6 +796,14 @@ static void virtio_net_set_features(VirtIODevice *vdev, uint64_t features) > > > > > > > > } else { > > > > > > > > memset(n->vlans, 0xff, MAX_VLAN >> 3); > > > > > > > > } > > > > > > > > + > > > > > > > > + if (virtio_has_feature(features, VIRTIO_NET_F_STANDBY)) { > > > > > > > > + atomic_set(&n->primary_should_be_hidden, false); > > > > > > > > + if (n->primary_device_timer) > > > > > > > > + timer_mod(n->primary_device_timer, > > > > > > > > + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + > > > > > > > > + 4000); > > > > > > > > + } > > > > > > > > > > > > > > What's this magic timer constant and why? > > > > > > > > > > To be honest it's a leftover from previous versions (before I took > > > > > over) of the patches and I'm not sure why the timer is there. > > > > > I removed it and so far see no reason to keep it. > > > > > > > > > > > > > > > > > > > > } > > > > > > > > > > > > > > > > static int virtio_net_handle_rx_mode(VirtIONet *n, uint8_t cmd, > > > > > > > > @@ -2626,6 +2644,87 @@ void virtio_net_set_netclient_name(VirtIONet *n, const char *name, > > > > > > > > n->netclient_type = g_strdup(type); > > > > > > > > } > > > > > > > > > > > > > > > > +static void virtio_net_primary_plug_timer(void *opaque) > > > > > > > > +{ > > > > > > > > + VirtIONet *n = opaque; > > > > > > > > + Error *err = NULL; > > > > > > > > + > > > > > > > > + if (n->primary_device_dict) > > > > > > > > + n->primary_device_opts = qemu_opts_from_qdict(qemu_find_opts("device"), > > > > > > > > + n->primary_device_dict, &err); > > > > > > > > + if (n->primary_device_opts) { > > > > > > > > + n->primary_dev = qdev_device_add(n->primary_device_opts, &err); > > > > > > > > + error_setg(&err, "virtio_net: couldn't plug in primary device"); > > > > > > > > + return; > > > > > > > > + } > > > > > > > > + if (!n->primary_device_dict && err) { > > > > > > > > + if (n->primary_device_timer) { > > > > > > > > + timer_mod(n->primary_device_timer, > > > > > > > > + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + > > > > > > > > + 100); > > > > > > > > > > > > > > same here. > > > > > > > > > > see above > > > > > > > > > > > > > > > > > > > > > > > > > > > + } > > > > > > > > + } > > > > > > > > +} > > > > > > > > + > > > > > > > > +static void virtio_net_handle_migration_primary(VirtIONet *n, > > > > > > > > + MigrationState *s) > > > > > > > > +{ > > > > > > > > + Error *err = NULL; > > > > > > > > + bool should_be_hidden = atomic_read(&n->primary_should_be_hidden); > > > > > > > > + > > > > > > > > + n->primary_dev = qdev_find_recursive(sysbus_get_default(), > > > > > > > > + n->primary_device_id); > > > > > > > > + if (!n->primary_dev) { > > > > > > > > + error_setg(&err, "virtio_net: couldn't find primary device"); > > > > > > > > > > > > > > There's something broken with the error handling in this function - the > > > > > > > 'err' never goes anywhere - I don't think it ever gets printed or > > > > > > > reported or stops the migration. > > > > > > > > > > yes, I'll fix it. > > > > > > > > > > > > > + } > > > > > > > > + if (migration_in_setup(s) && !should_be_hidden && n->primary_dev) { > > > > > > > > + qdev_unplug(n->primary_dev, &err); > > > > > > > > > > > > > > Not knowing unplug well; can you just explain - is that device hard > > > > > > > unplugged and it's gone by the time this function returns or is it still > > > > > > > hanging around for some indeterminate time? > > > > > > > > > > Qemu will trigger an unplug request via pcie attention button in which case > > > > > there could be a delay by the guest operating system. We could give it some > > > > > amount of time and if nothing happens try surpise removal or handle the > > > > > error otherwise. > > > > > > > > > > > > > > > regards, > > > > > Jens > > > > > > > > That's a subject for another day. Let's get the basic thing > > > > working. > > > > > > Well no, we need to know this thing isn't going to hang in the migration > > > setup phase, or if it does how we recover. > > > > > > This thing is *supposed* to be stuck in migration startup phase > > if guest is malicious. > > > > If migration does not progress management needs > > a way to detect this and cancel. > > > > Some more documentation about how this is supposed to happen > > would be helpful. > > I want to see that first; because I want to convinced it's just a > documentation problem and that we actually really have a method of > recovering. > > > > This patch series is very > > > odd precisely because it's trying to do the unplug itself in the > > > migration phase rather than let the management layer do it - so unless > > > it's nailed down how to make sure that's really really bullet proof > > > then we've got to go back and ask the question about whether we should > > > really fix it so it can be done by the management layer. > > > > > > Dave > > > > management already said they can't because files get closed and > > resources freed on unplug and so they might not be able to re-add device > > on migration failure. We do it in migration because that is > > where failures can happen and we can recover. > > I find this explanation confusing - I can kind of see where it's coming > from, but we've got a pretty clear separation between a NIC and the > netdev that backs it; those files and resources should be associated > with the netdev and not the NIC. So does hot-removing the NIC really > clean up the netdev? (I guess maybe this is a different in vfio > which is the problem) > > Dave what we are removing is the VFIO device. Nothing to do with nic or netdev. > > > > -- > > > > MST > > > -- > > > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK