Re: [Qemu-devel] [RFC PATCH 3/4] pc: acpi: add _CST support

[Igor Mammedov]

On Wed, 8 Aug 2018 23:17:48 +0300
"Michael S. Tsirkin" <address@hidden> wrote:

> On Wed, Aug 08, 2018 at 05:15:48PM +0200, Igor Mammedov wrote:
> > Reuse CPU hotplug IO registers for passing a CST entry
> > containing package for shalowest C1 using mwait and
> > read it out in guest with new CCST AML method.  
> 
> I don't see how 1 entry is enough. We need to describe full _CST package so
> that guest can do reasonable power management on the CPU.
I was assuming that CST are to be used for mwait/monitor idle combo
to help reduce latencies/vmexits on cpus wakeup from idle state, hence 1 entry.
It's trivial to add as much as needed entries though.
If you are fine with approach I can respin patch with arbitrary
number of CStates.
 
> > The CState support is optional and could be turned on
> > with '-global PIIX4_PM.cstate=on' CLI option.
> > 
> > Signed-off-by: Igor Mammedov <address@hidden>
> > ---
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