Re: question regarding intel_idle inside kvm

[Avi Kivity <avi@redhat.com>]

On 03/16/2012 12:19 AM, Daniel Lezcano wrote:
> Hi all,
>
> I recently did some modification in the cpuidle core and the patches
> were merge to linux-next.
> Someone reported a problem with the intel_idle cpuidle driver.
>
> I tried to reproduce the problem with kvm but the kernel fails to
> intialize the driver because of intel_intel_init function fails in the
> processor probe.
>
> After digging a bit, I found it fails at:
>
> drivers/idle/intel_idle.c
>
> static int intel_idle_probe(void)
> {
>
> ...
>
>
>         if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
>                 return -ENODEV;
>
>         ^^^^^
>
>  ...
>
> }
>
> I assumed the virtualized processor does not support this, so I
> specified the "-cpu host" because the host was running the intel_idle
> driver. But the driver still fails in kvm.
>
> I was wondering why that happens ? Does anyone have an idea of this
> problem ?

intel_idle() uses mwait, which kvm does not virtualize (it's very
expensive to do so and brings no benefits).

-- 
error compiling committee.c: too many arguments to function