Re: [libvirt] [PATCH RFC] libxl: reverse defaults on HVM net device attach

libvirt libxl picks its own default with respect to the default NIC to use. libxlMakeNic is the one responsible for this and on boot it picks LIBXL_NIC_TYPE_VIF_IOEMU such that it accomodates both PV and emulated one. The good behaving guest at boot will then select the pv and unplug the emulated device.

Now, on HVM when attaching an interface it will pick the same default that is LIBXL_NIC_TYPE_VIF_IOEMU which as a result will fail the attach (see xen commit 32e9d0f ("libxl: nic type defaults to vif in hotplug for hvm guest"). Xen doesn't yet support the hotplug of emulated devices, but we don't want to rule out that case either, which might get support in the future. Hence we simply reverse the defaults when we are attaching the interface which allows libvirt to prefer the PV nic first without adding "model='netfront'" following the same pattern as above commit. Also to avoid ruling out the emulated one we set to LIBXL_NIC_TYPE_IOEMU when setting a model type that is not 'netfront'. Signed-off-by: Joao Martins <joao.m.martins(a)oracle.com&gt; --- This allows Openstack to attach network interfaces, which currently is broken on libxl if it doesn't set model 'netfront'. I am not sure whether this is the best way (hence RFC) or if users should really be setting the model='netfront' when attaching devices. But sounds to me that it would be better to have by default the supported, and if users want emulated attach to specify a nic model. Thoughts? --- src/libxl/libxl_conf.c | 9 ++++++--- src/libxl/libxl_conf.h | 3 ++- src/libxl/libxl_driver.c | 2 +- 3 files changed, 9 insertions(+), 5 deletions(-) diff --git a/src/libxl/libxl_conf.c b/src/libxl/libxl_conf.c index dcf8e7e..50aa958 100644 --- a/src/libxl/libxl_conf.c +++ b/src/libxl/libxl_conf.c @@ -881,9 +881,10 @@ libxlMakeDiskList(virDomainDefPtr def, libxl_domain_config *d_config) int libxlMakeNic(virDomainDefPtr def, virDomainNetDefPtr l_nic, - libxl_device_nic *x_nic) + libxl_device_nic *x_nic, + bool attach) { - bool ioemu_nic = def->os.type == VIR_DOMAIN_OSTYPE_HVM; + bool ioemu_nic = def->os.type == VIR_DOMAIN_OSTYPE_HVM && !attach; virDomainNetType actual_type = virDomainNetGetActualType(l_nic); virNetworkPtr network = NULL; virConnectPtr conn = NULL; @@ -917,6 +918,8 @@ libxlMakeNic(virDomainDefPtr def, goto cleanup; if (STREQ(l_nic->model, "netfront")) x_nic->nictype = LIBXL_NIC_TYPE_VIF; + else + x_nic->nictype = LIBXL_NIC_TYPE_VIF_IOEMU; } if (VIR_STRDUP(x_nic->ifname, l_nic->ifname) < 0) @@ -1047,7 +1050,7 @@ libxlMakeNicList(virDomainDefPtr def, libxl_domain_config *d_config) if (virDomainNetGetActualType(l_nics[i]) == VIR_DOMAIN_NET_TYPE_HOSTDEV) continue; - if (libxlMakeNic(def, l_nics[i], &x_nics[nvnics])) + if (libxlMakeNic(def, l_nics[i], &x_nics[nvnics], false)) goto error; /* * The devid (at least right now) will not get initialized by diff --git a/src/libxl/libxl_conf.h b/src/libxl/libxl_conf.h index 0ea76b4..851f3af 100644 --- a/src/libxl/libxl_conf.h +++ b/src/libxl/libxl_conf.h @@ -178,7 +178,8 @@ libxlMakeDisk(virDomainDiskDefPtr l_dev, libxl_device_disk *x_dev); int libxlMakeNic(virDomainDefPtr def, virDomainNetDefPtr l_nic, - libxl_device_nic *x_nic); + libxl_device_nic *x_nic, + bool attach); int libxlMakeVfb(virPortAllocatorPtr graphicsports, virDomainGraphicsDefPtr l_vfb, libxl_device_vfb *x_vfb); diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c index b19b17e..7e5d9b6 100644 --- a/src/libxl/libxl_driver.c +++ b/src/libxl/libxl_driver.c @@ -3379,7 +3379,7 @@ libxlDomainAttachNetDevice(libxlDriverPrivatePtr driver, goto cleanup; } - if (libxlMakeNic(vm->def, net, &nic) < 0) + if (libxlMakeNic(vm->def, net, &nic, true) < 0) goto cleanup; if (libxl_device_nic_add(cfg->ctx, vm->def->id, &nic, 0)) {