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Re: [libvirt] [PATCH 0/2] Xen: Add support for interface model='netfront'



On Fri, Nov 27, 2009 at 07:00:47PM +0100, Jiri Denemark wrote:
> Xen HVM guests with PV drivers end up with two network interfaces for
> each configured interface. One of them being emulated by qemu and the
> other one paravirtual. As this might not be desirable, the attached
> patch provides a way for users to specify that only paravirtual network
> interface should be presented to the guest.
> 
> The configuration was inspired by qemu/kvm driver, for which users can
> specify model='virtio' to use paravirtual network interface.
> 
> The patch adds support for model='netfront' which results in
> type=netfront instead of type=ioemu (or nothing for newer xen versions)
> in guests native configuration. Xen's qemu ignores interfaces with
> type != ioemu and only paravirtual network device will be seen in the
> guest.
> 
> Four possible configuration scenarios follow:
> 
> - no model specified in domain's XML
>     - libvirt will behave like before this change; it will set
>       type=ioemu for HVM guests on xen host which is not newer than
>       XEND_CONFIG_MAX_VERS_NET_TYPE_IOEMU
>     - covered by existing tests
> 
> - PV guest, any model
>     - no functional change, model is passed as is (and ignored by the
>       hypervisor)
>     - covered by existing tests (e.g., *-net-e1000.*)
> 
> - HVM guest, model=netfront
>     - type is set to "netfront", model is not specified
>     - covered by new *-net-netfront.* tests
> 
> - HVM guest, model != netfront
>     - type is set to "ioemu", model is passed as is
>     - covered by new *-net-ioemu.* tests
> 
> The fourth scenario feels like a regression for xen newer than
> XEND_CONFIG_MAX_VERS_NET_TYPE_IOEMU as users who had a model specified
> in their guest's configuration won't see a paravirtual interface in
> their guests any more. On the other hand, the reason for specifying a
> model is most likely the fact that they want to use such model which
> implies emulated interface. Users of older xen won't be affected at all
> as their xen provides paravirtual interface regardless of the type used.
> 
> In previous version of this patch, I used "xenpv" instead of "netfront"
> as it looked more like kvm/qemu's virtio. However, you can find several
> tips how to force PV network interface for HVM guest by using
> type="netfront" so I changed it to conform with those tips. It also
> matches guest's driver name used for that device.
> 
> Jiri Denemark (2):
>   Support for interface model='netfront'
>   Tests for interface type/model configuration

  Thanks for the thorough explanations, I pushed both patches !

Daniel

-- 
Daniel Veillard      | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
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