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

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Wed, Oct 26, 2011 at 03:47:13PM +0100, Alex Bligh wrote:
> 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)?
>

Nope. PVHVM drivers will require the xen pci platform device to operate.

-- Pasi


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