On 12/09/2016 11:35 AM, Joao Martins wrote:
> 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.
Short note, in this paragraph I meant for HVM guest. For PV this isn't
applicable. I can correct the commit message and resend after
comments (depending ofc if folks think this is right way to go).
> 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.mart...@oracle.com>
> ---
>
> 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)) {
>
--
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