Re: [Xen-users] Release 0.8.9 of GPL PV drivers for Windows

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Wed, May 07, 2008 at 04:58:43PM +1000, James Harper wrote:
> > 
> > And more thing for the number of vcpu's for the HVM guest.. I think
> > Windows
> > installs UNI or SMP HAL during the install time.. I don't know what kind
> > of
> > effect there is if you run SMP HAL with only a single (v)CPU ?
> > 
> 
> The first time you start a previously UP windows DomU with more than a single 
> vcpu, 
> you get a message like 'your system must be rebooted for your new hardware to 
> complete installation', and sure enough you don't see the additional CPU(s) 
> in 
> process monitor until you reboot.
> 
> Subsequent changes to and from SMP don't do the same thing, so it is possible 
> that the first time you boot with >1 cpu an SMP hal gets installed, and that 
> it 
> doesn't get uninstalled afterwards... In a physical as opposed to virtual 
> environment 
> this kind of makes sense - how often are you going to take an SMP machine 
> back to 
> a single processor unless you have a hardware failure or something, which 
> will 
> probably only be temporary anyway until the replacement cpu arrives?
> 

Yep.

Do you know if running the SMP HAL with just a single vcpu will cause any
performance degrations? 

-- Pasi

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