Xen Virtio Drivers

Xen Virtio Drivers

[Volo M.]

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Hi Devs,

Could you please help me to identify right way to start using Virtio
drivers for Xen guests
as described here https://wiki.xen.org/wiki/QEMU_Upstream .
I've managed to start my Windows 2008 VM with Virtio network drivers by
using 'model='virtio-net'' option as described above and it works fine (but
only for network interfaces).

The problem is I still can't identify how to make Xen using virtio-blk or
virtio-scsi backend for 'qemu-xen' qemu-model as mentioned here
https://en.wikibooks.org/wiki/QEMU/Devices/Virtio which should be
compatible with 'qemu-xen' qemu upstream model.

I can't see any mention about virtio disk types in docs:
https://xenbits.xen.org/docs/4.8-testing/misc/xl-disk-configuration.txt   .
Also I've done very common check through Xen source code ('*/tools/libxl/*'
area) while looking how to apply virtio disk drivers for our Xen guests.

Can you please clarify if it's been ever implemented. Do you have any ETA
when it's going to be implemented...etc? Or probably you could give me any
advice how to make it working?

Thanks a lot in advance.

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Re: Xen Virtio Drivers

[Konrad Rzeszutek Wilk]

On Wed, Mar 07, 2018 at 04:13:47PM +0200, Volo M. wrote:
> Hi Devs,
> 
> Could you please help me to identify right way to start using Virtio
> drivers for Xen guests
> as described here https://wiki.xen.org/wiki/QEMU_Upstream .
> I've managed to start my Windows 2008 VM with Virtio network drivers by
> using 'model='virtio-net'' option as described above and it works fine (but
> only for network interfaces).
> 
> The problem is I still can't identify how to make Xen using virtio-blk or
> virtio-scsi backend for 'qemu-xen' qemu-model as mentioned here
> https://en.wikibooks.org/wiki/QEMU/Devices/Virtio which should be
> compatible with 'qemu-xen' qemu upstream model.
> 
> I can't see any mention about virtio disk types in docs:
> https://xenbits.xen.org/docs/4.8-testing/misc/xl-disk-configuration.txt   .
> Also I've done very common check through Xen source code ('*/tools/libxl/*'
> area) while looking how to apply virtio disk drivers for our Xen guests.
> 
> Can you please clarify if it's been ever implemented. Do you have any ETA
> when it's going to be implemented...etc? Or probably you could give me any
> advice how to make it working?

IT all works with HVM guests. You do have to tweak the Xen build of qemu
to build with KVM enabled (oddly enough the Virtio drivers depend on that
right now).

> 
> Thanks a lot in advance.

> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xenproject.org
> https://lists.xenproject.org/mailman/listinfo/xen-devel


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Re: Xen Virtio Drivers

[Volo M.]

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Thanks,

Cool, I'll have to check how to tweak xen build.

Will I have to change below disk lines of XL toolkit VM config somehow to
enable using Virtio drives emulation
 or custom xen build just enable it by those kvm-enabled tweak for all HVM
guests within hypervisor?

vif = [ "model=virtio-net, mac=00:16:3e:11:77:f0, bridge=officevswitch1,
ip=10.91.0.224, vifname=cxqastfflivgrl" ]
disk = [
"format=raw,vdev=hda,access=rw,backendtype=phy,target=/dev/iscsistore02/disk1237"
]
disk = [ "phy:/dev/iscsistore02/disk1238,ioemu:hda,w" ]


On Wed, Mar 7, 2018 at 5:08 PM, Konrad Rzeszutek Wilk <
konrad.wilk@oracle.com> wrote:

> On Wed, Mar 07, 2018 at 04:13:47PM +0200, Volo M. wrote:
> > Hi Devs,
> >
> > Could you please help me to identify right way to start using Virtio
> > drivers for Xen guests
> > as described here https://wiki.xen.org/wiki/QEMU_Upstream .
> > I've managed to start my Windows 2008 VM with Virtio network drivers by
> > using 'model='virtio-net'' option as described above and it works fine
> (but
> > only for network interfaces).
> >
> > The problem is I still can't identify how to make Xen using virtio-blk or
> > virtio-scsi backend for 'qemu-xen' qemu-model as mentioned here
> > https://en.wikibooks.org/wiki/QEMU/Devices/Virtio which should be
> > compatible with 'qemu-xen' qemu upstream model.
> >
> > I can't see any mention about virtio disk types in docs:
> > https://xenbits.xen.org/docs/4.8-testing/misc/xl-disk-configuration.txt
>  .
> > Also I've done very common check through Xen source code
> ('*/tools/libxl/*'
> > area) while looking how to apply virtio disk drivers for our Xen guests.
> >
> > Can you please clarify if it's been ever implemented. Do you have any ETA
> > when it's going to be implemented...etc? Or probably you could give me
> any
> > advice how to make it working?
>
> IT all works with HVM guests. You do have to tweak the Xen build of qemu
> to build with KVM enabled (oddly enough the Virtio drivers depend on that
> right now).
>
> >
> > Thanks a lot in advance.
>
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@lists.xenproject.org
> > https://lists.xenproject.org/mailman/listinfo/xen-devel
>
>

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Re: Xen Virtio Drivers

[Christopher Clark]

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On Wed, Mar 7, 2018 at 6:13 AM, Volo M. <vm@vovs.net> wrote:

> Hi Devs,
>
> Could you please help me to identify right way to start using Virtio
> drivers for Xen guests
>



















*HiThis reply might not be the answer that you’re looking for, but it may
be helpful for the next person arriving via searching with a similar Virtio
driver query.If you can, using the native Xen device drivers in your
Windows VM is preferable to using Virtio, and there’s a driver set
available at: https://www.xenproject.org/downloads/windows-pv-drivers.html
<https://www.xenproject.org/downloads/windows-pv-drivers.html>and more info
at: https://www.xenproject.org/developers/teams/windows-pv-drivers.html
<https://www.xenproject.org/developers/teams/windows-pv-drivers.html>Alternatively,
Citrix’s XenServer also has a set of Xen PV drivers for Windows
VMs.Virtio's design requires that the domain where the Virtio device is
emulated (where QEMU is running) has full privileges over the VM using the
Virtio driver -- ie. is able to map any memory inside that VM. This
requirement is contrary to the security model of a type-1 hypervisor such
as Xen, and is not necessary: Xen's native device drivers are performant
and don't need it, and they are compatible with deprivileged Driver
Domains.Driver domains are important for many Xen deployments -- for
example, OpenXT and Qubes OS use network driver
domains:https://wiki.xenproject.org/wiki/Driver_Domain
<https://wiki.xenproject.org/wiki/Driver_Domain>https://www.slideshare.net/xen_com_mgr/the-openxt-project-in-2016-christopher-clark-bae-systems/15
<https://www.slideshare.net/xen_com_mgr/the-openxt-project-in-2016-christopher-clark-bae-systems/15>https://www.qubes-os.org/doc/networking/
<https://www.qubes-os.org/doc/networking/>In addition to security
architecture, there is a question of performance:the Virtio protocols are
optimized for -- and can work well with -- hosted Type-2 hypervisors, but
being implemented in QEMU they tend to become a performance bottleneck in
Xen deployments where Dom0 is usually only one of many domains, and
possibly not the largest.Significant development effort on Xen has gone
into isolating and deprivileging the QEMU device emulator (stubdomains,
dm_ops, dropping privileges, non-root QEMU, SELinux and XSM policy, ...) to
reduce attack surface.Running VMs without QEMU at all whenever possible is
a valued capability.Finally, although Virtio is often presented as a
paravirtualized solution, it requires an emulation infrastructure that is
not otherwise necessary - and so it is not compatible with PV and PVH
guests on x86, or at all on ARM, because of this requirement.A reference to
a related earlier discussion thread:https://lists.gt.net/xen/devel/318380
<https://lists.gt.net/xen/devel/318380>Christopher*

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