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

To: Pasi Kärkkäinen <pasik@xxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Subject: Re: [Xen-devel] xen_emul_unplug on xen 4.1, HVM guest 2.6.38
From: Alex Bligh <alex@xxxxxxxxxxx>
Date: Wed, 26 Oct 2011 15:47:13 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Alex Bligh <alex@xxxxxxxxxxx>
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Pasi, Conrad,

--On 26 October 2011 17:12:33 +0300 Pasi Kärkkäinen <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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