[Xen-devel] Re: expose MWAIT to dom0

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 15/08/2011 08:13, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:

>> Well the problem is some older kernels will try to use MWAIT if they see the
>> feature in CPUID. Of course that doesn't work outside ring 0.
>> 
> 
> if those old kernels are still of interest, then possibly a boot option in Xen
> would
> be applausive. Or can we just allow selectively exposing MWAIT when xen
> cpuidle is enabled?

The kernel could unconditionally advertise MWAIT from its cpuid pv_ops hook?
If all that's doing is causing relevant parts of BIOS tables to be parsed,
would that be safe when MWAIT is not in fact available?

Else the kernel could get the flag from the real non paravirtualised CPUID
instruction.

 -- Keir



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