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

To: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Subject: Re: [Xen-devel] xen_emul_unplug on xen 4.1, HVM guest 2.6.38
From: Pasi Kärkkäinen <pasik@xxxxxx>
Date: Wed, 26 Oct 2011 17:12:33 +0300
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Alex Bligh <alex@xxxxxxxxxxx>
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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

:)

-- Pasi


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