Re: [Xen-devel] xen_emul_unplug on xen 4.1, HVM guest 2.6.38

[Alex Bligh <alex@xxxxxxxxxxx>]

Pasi, Conrad,

--On 26 October 2011 17:12:33 +0300 Pasi KÃrkkÃinen <pasik@xxxxxx> wrote:

> On Wed, Oct 26, 2011 at 09:49:42AM -0400, Konrad Rzeszutek Wilk wrote:
> > On Wed, Oct 26, 2011 at 02:17:25PM +0100, Alex Bligh wrote:
> > > I am running Xen 4 and want users to be able to install arbitrary HVM
> > > images. We want both PV and emulated drivers to appear. The reason
> > > for this is for compatibility with images that were prepared for
> > > Xen 3.3, which assume emulated devices exist at boot time (particularly
> > > for running the boot loader).
> > >
> > > If I do not specify on the boot line xen_emul_unplug=never, then
> > > under some guest OS's (e.g. Ubuntu Natty (2.6.38)), the domU kernel
> > > unplugs the non-PV devices, which is undesirable in my application.
> > >
> > > I cannot arbitrarily change the kernel command line because it is
> > > in effect set by the user's image.
> > >
> > > Therefore what I need to do is prevent Xen4 offering the facility
> > > to unplug the devices in the first place. Setting "(unpluggable 0)"
> > > in the config for the emulated NICs and disks does not appear
> > > to prevent them getting unplugged; what may be happening is that
> > > domU tries to unplug them (but fails) but still doesn't use them.
> > > Is there a way to signal from dom0 that the kernel really shouldn't
> > > unplug this stuff.
> >
> > xen_pci_platform=0 in your guest config should do it.
> It's actually called:
> xen_platform_pci=0
Thanks. Just to confirm, that will still allow HVM PV drivers to
operate (as well)?

--
Alex Bligh

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