[Xen-devel] Re: expose MWAIT to dom0

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 15/08/2011 08:57, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:

>> Else the kernel could get the flag from the real non paravirtualised CPUID
>> instruction.
> 
> linux uses cpu_has to extract mwait capability. To use real cpuid instruction,
> then
> we need change Linux code which is not worthy though, like below:
>        if (!cpu_has(c, X86_FEATURE_MWAIT))
>                buf[2] &= ~(ACPI_PDC_C_C2C3_FFH);
> If we make it into cpu_has bits, then it lacks of original guarding effect.

cpu_has() accesses a pre-filled capabilities bitmask, filled from cpuid,
right? And cpuid goes through a pv_ops hook?

 -- Keir



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