February 2011 - Devel - libvirt List Archives

[libvirt] [PATCH] Fix python error reporting for some storage operations
by Cole Robinson 07 Mar '25

07 Mar '25

In the python bindings, all vir* classes expect to be passed a virConnect object when instantiated. Before the storage stuff, these classes were only instantiated in virConnect methods, so the generator is hardcoded to pass 'self' as the connection instance to these classes. Problem is there are some methods that return pool or vol instances which aren't called from virConnect: you can lookup a storage volume's associated pool, and can lookup volumes from a pool. In these cases passing 'self' doesn't give the vir* instance a connection, so when it comes time to raise an exception crap hits the fan. Rather than rework the generator to accomodate this edge case, I just fixed the init functions for virStorage* to pull the associated connection out of the passed value if it's not a virConnect instance. Thanks, Cole diff --git a/python/generator.py b/python/generator.py index 01a17da..c706b19 100755 --- a/python/generator.py +++ b/python/generator.py @@ -962,8 +962,12 @@ def buildWrappers(): list = reference_keepers[classname] for ref in list: classes.write(" self.%s = None\n" % ref[1]) - if classname in [ "virDomain", "virNetwork", "virStoragePool", "virStorageVol" ]: + if classname in [ "virDomain", "virNetwork" ]: classes.write(" self._conn = conn\n") + elif classname in [ "virStorageVol", "virStoragePool" ]: + classes.write(" self._conn = conn\n" + \ + " if not isinstance(conn, virConnect):\n" + \ + " self._conn = conn._conn\n") classes.write(" if _obj != None:self._o = _obj;return\n") classes.write(" self._o = None\n\n"); destruct=None

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[libvirt] [PATCH] web docs -- macvtap mode explanation
by Stefan Berger 27 Oct '23

27 Oct '23

This adds more information about the different macvtap device modes. Regards, Stefan

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[libvirt] Supporting vhost-net and macvtap in libvirt for QEMU
by Anthony Liguori 27 Oct '23

27 Oct '23

Disclaimer: I am neither an SR-IOV nor a vhost-net expert, but I've CC'd people that are who can throw tomatoes at me for getting bits wrong :-) I wanted to start a discussion about supporting vhost-net in libvirt. vhost-net has not yet been merged into qemu but I expect it will be soon so it's a good time to start this discussion. There are two modes worth supporting for vhost-net in libvirt. The first mode is where vhost-net backs to a tun/tap device. This is behaves in very much the same way that -net tap behaves in qemu today. Basically, the difference is that the virtio backend is in the kernel instead of in qemu so there should be some performance improvement. Current, libvirt invokes qemu with -net tap,fd=X where X is an already open fd to a tun/tap device. I suspect that after we merge vhost-net, libvirt could support vhost-net in this mode by just doing -net vhost,fd=X. I think the only real question for libvirt is whether to provide a user visible switch to use vhost or to just always use vhost when it's available and it makes sense. Personally, I think the later makes sense. The more interesting invocation of vhost-net though is one where the vhost-net device backs directly to a physical network card. In this mode, vhost should get considerably better performance than the current implementation. I don't know the syntax yet, but I think it's reasonable to assume that it will look something like -net tap,dev=eth0. The effect will be that eth0 is dedicated to the guest. On most modern systems, there is a small number of network devices so this model is not all that useful except when dealing with SR-IOV adapters. In that case, each physical device can be exposed as many virtual devices (VFs). There are a few restrictions here though. The biggest is that currently, you can only change the number of VFs by reloading a kernel module so it's really a parameter that must be set at startup time. I think there are a few ways libvirt could support vhost-net in this second mode. The simplest would be to introduce a new tag similar to <source network='br0'>. In fact, if you probed the device type for the network parameter, you could probably do something like <source network='eth0'> and have it Just Work. Another model would be to have libvirt see an SR-IOV adapter as a network pool whereas it handled all of the VF management. Considering how inflexible SR-IOV is today, I'm not sure whether this is the best model. Has anyone put any more thought into this problem or how this should be modeled in libvirt? Michael, could you share your current thinking for -net syntax? -- Regards, Anthony Liguori

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[libvirt] [PATCH 0/4] Multiple problems with saving to block devices
by Daniel P. Berrange 24 Mar '13

24 Mar '13

This patch series makes it possible to save to a block device, instead of a plain file. There were multiple problems - WHen save failed, we might de-reference a NULL pointer - When save failed, we unlinked the device node !! - The approach of using >> to append, doesn't work with block devices - CGroups was blocking QEMU access to the block device when enabled One remaining problem is not in libvirt, but rather QEMU. The QEMU exec: based migration often fails to detect failure of the command and will thus hang forever attempting a migration that'll never succeed! Fortunately you can now work around this in libvirt using the virsh domjobabort command

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[libvirt] I need help for use virDomainInterfaceStats
by Фёдор Пранович 03 Apr '12

03 Apr '12

Hi I want use the virDomainInterfaceStats for get statistic of domain, but I don't now how get path parametr. Please help me! Thanks.

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[libvirt] libvirt(-java): virDomainMigrateSetMaxDowntime
by Thomas Treutner 15 Sep '11

15 Sep '11

Hi, I'm facing some troubles with virDomainMigrate & virDomainMigrateSetMaxDowntime. The core problem is that KVM's default value for the maximum allowed downtime is 30ms (max_downtime in migration.c, it's nanoseconds there; 0.12.3) which is too low for my VMs when they're busy (~50% CPU util and above). Migrations then take literally forever, I had to abort them after 15 minutes or so. I'm using GBit Ethernet, so plenty bandwidth should be available. Increasing the allowed downtime to 50ms seems to help, but I have not tested situations where the VM is completely utilized. Anyways, the default value is too low for me, so I tried virDomainMigrateSetMaxDowntime resp. the Java wrapper function. Here I'm facing a problem I can overcome only with a quite crude hack: org.libvirt.Domain.migrate(..) blocks until the migration is done, which is of course reasonable. So I tried calling migrateSetMaxDowntime(..) before migrating, causing an error: "Requested operation is not valid: domain is not being migrated" This tells me that calling migrateSetMaxDowntime is only allowed during migrations. As I'm migrating VMs automatically and without any user intervention I'd need to create some glue code that runs in an extra thread, waiting "some time" hoping that the migration was kicked off in the main thread yet and then calling migrateSetMaxDowntime. I'd like to avoid such quirks in the long run, if possible. So my question: Would it be possible to extend the migrate() method resp. virDomainMigrate() function with an optional maxDowntime parameter that is passed down as QEMU_JOB_SIGNAL_MIGRATE_DOWNTIME so that qemuDomainWaitForMigrationComplete would set the value? Or are there easier ways? Thanks and regards, -t

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[libvirt] snapshots += domain description?
by Philipp Hahn 15 Aug '11

15 Aug '11

Hello, I just encountered a problem with the current snapshot implementation for qemu/kvm: To revert back to a snapshot, the domain description must closely match the domain description when the snapshot was created. If the ram-size doesn't match or the VM now contains fewer CPUs or contains additional disks, kvm will either not load the snapshot or the machine will be broken afterwarts. Is this a known problem? Without looking into the implementation details I think saving the full domain description instead of just a reference to the domain uuid as part of the snapshot description would work better. Or am I supposed to save the domain description myself in addition the the data saved in /var/lib/libvirt/qemu/snapshot/$DOMAIN_NAME/$SNAPSHOT_NAME.xml. I think this is very important feature, because when you - for example - notice that you need additional disk space and would like to include an additional block device, this is your ideal time to take a snapshot you can revert to when you do something wrong. Looking at VMware I see that reverting a VM there will not only revert the disks and ram back to the saved state, but also the description including name, ram size, etc. Any comment or advise is appreciated. Sincerely Philipp Hahn -- Philipp Hahn Open Source Software Engineer hahn(a)univention.de Univention GmbH Linux for Your Business fon: +49 421 22 232- 0 Mary-Somerville-Str.1 28359 Bremen fax: +49 421 22 232-99 http://www.univention.de

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[libvirt] (how much) support for kqemu domain
by John Lumby 06 Jun '11

06 Jun '11

I am wondering about the extent to which "old" qemu-0.11.1 and kqemu-1.4.0 are supported by virt-manager. I see I can specify --virt-type=kqemu on virt-install and it remembers domain type='kqemu', and does things such as refusing to start the vm if the kqemu kernel mod not loaded, but it seems it does not tack on the -enable-kqemu -kernel-kqemu options on to the qemu command line. There is really not much point in trying to start a qemu-based vm with neither hardware kvm nor kqemu ... I can work around it with an override script to intercept the qemu command, but does anyone think virt-manager ought to do this for me? John Lumby _________________________________________________________________

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[libvirt] [PATCH 0/6] Introduce a new migration protocol to QEMU driver
by Daniel P. Berrange 05 May '11

05 May '11

The current migration protocol has several flaws - No initial hook on the source host to do work before the dst VM is launched - No ability to restart src VM if dst fails to recv all migration data, but src successfully sent it all This introduces a new 5 step migration process to address this limitation. To support features such as seemless migration of SPICE clients, and lock driver state passing this now makes use of the migration cookie feature too

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[libvirt] [PATCH V2] xen: check if device is assigned to guest before reattaching
by Yufang Zhang 27 Apr '11

27 Apr '11

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=664059 This is the version2 patch for BZ#664059. Reattaching pci device back to host without destroying guest or detaching device from guest would cause host to crash. This patch adds a check before doing device reattach. If the device is being assigned to guest, libvirt refuses to reattach device to host. The patch only works for Xen, for it just checks xenstore to get pci device information. Signed-off-by: Yufang Zhang <yuzhang(a)redhat.com> --- src/xen/xen_driver.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 67 insertions(+), 0 deletions(-) diff --git a/src/xen/xen_driver.c b/src/xen/xen_driver.c index 4c11b11..318bb6a 100644 --- a/src/xen/xen_driver.c +++ b/src/xen/xen_driver.c @@ -1891,11 +1891,70 @@ out: } static int +xenUnifiedNodeDeviceAssignedDomainId (virNodeDevicePtr dev) +{ + int numdomains; + int ret = -1, i; + int *ids = NULL; + char *bdf = NULL; + char *xref = NULL; + unsigned int domain, bus, slot, function; + virConnectPtr conn = dev->conn; + xenUnifiedPrivatePtr priv = conn->privateData; + + /* Get active domains */ + numdomains = xenUnifiedNumOfDomains(conn); + if (numdomains < 0) { + return ret; + } + if (numdomains > 0){ + if (VIR_ALLOC_N(ids, numdomains) < 0){ + virReportOOMError(); + goto out; + } + if ((numdomains = xenUnifiedListDomains(conn, &ids[0], numdomains)) < 0){ + goto out; + } + } + + /* Get pci bdf */ + if (xenUnifiedNodeDeviceGetPciInfo(dev, &domain, &bus, &slot, &function) < 0) + goto out; + + if (virAsprintf(&bdf, "%04x:%02x:%02x.%0x", + domain, bus, slot, function) < 0) { + virReportOOMError(); + goto out; + } + + /* Check if bdf is assigned to one of active domains */ + for (i = 0; i < numdomains; i++ ){ + xenUnifiedLock(priv); + xref = xenStoreDomainGetPCIID(conn, ids[i], bdf); + xenUnifiedUnlock(priv); + if (xref == NULL) + continue; + else { + ret = ids[i]; + break; + } + } + + VIR_FREE(xref); + VIR_FREE(bdf); +out: + VIR_FREE(ids); + + return ret; +} + +static int xenUnifiedNodeDeviceReAttach (virNodeDevicePtr dev) { pciDevice *pci; unsigned domain, bus, slot, function; int ret = -1; + int domid; if (xenUnifiedNodeDeviceGetPciInfo(dev, &domain, &bus, &slot, &function) < 0) return -1; @@ -1904,6 +1963,14 @@ xenUnifiedNodeDeviceReAttach (virNodeDevicePtr dev) if (!pci) return -1; + /* Check if device is assigned to an active guest */ + if ((domid = xenUnifiedNodeDeviceAssignedDomainId(dev)) >= 0){ + xenUnifiedError(VIR_ERR_INTERNAL_ERROR, + _("Device %s has been assigned to guest %d"), + dev->name, domid); + goto out; + } + if (pciReAttachDevice(pci, NULL) < 0) goto out; -- 1.7.3.4

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