Re: [Xen-devel] cpuid bit for relaxed timer handling?

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

Unfortunately it's not that easy since Xen's own CPUID leaves are in the way
and have to be relocated. Also if you advertise Viridian support in CPUID
then you also have to implement some hypervisor service calls.

Perhaps your best bet is to see if James Harper knows anything about BSODs
with GPLPV drivers on latest xen-unstable, and try to get that working?

 -- Keir

On 23/02/2009 05:02, "Andrew Lyon" <andrew.lyon@xxxxxxxxx> wrote:

> Hi,
> 
> I understand that with Xen 3.4 viridian=1 can be specified in the
> configugration file to enable viridian support, one of the effects of
> which is to set a cpuid bit to enable relaxed timers, I was wondering
> if the same bit could be set using the cpuid= setting on older
> versions of Xen?
> 
> I run Xen 3.2.1 and find that under heavy load my Windows 2008 and
> Vista VM's will BSOD with CLOCK_WATCHDOG_TIMEOUT (101), this is pretty
> inconvenient on its own but if the VM has a pci passthrough device the
> entire system will lock up when this happens, the same lockup happens
> if I destroy a VM which has a passthrough device.
> 
> I have tried running Xen unstable but when I install gplpv drivers my
> windows vm's BSOD with a 7E, I really need the performance boost of
> gplpv drivers or I would simply run unstable with no pv drivers.
> 
> Andy
> 
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