Re: [Qemu-devel] KVM guest cpu L3 cache and cpufreq

[Gleb Natapov]

On Mon, Aug 26, 2013 at 02:49:41PM +0200, Benoît Canet wrote:
> 
> Hi,
> 
> Thanks for the answer.
> 
> > On Tue, Aug 13, 2013 at 08:17:13PM +0200, Benoît Canet wrote:
> > > 
> > > Hi,
> > > 
> > > I noticed that the l3 cache size of a guest /proc/cpuinfo is not the same 
> > > as
> > > the l3 cache size of the host.
> > > 
> > > I did not found any references to this in the qemu and KVM code.
> > > 
> > > Is the size of the guest L3 cache fixed in hardware ?
> > > 
> > No, it is hardcoded somewhere in qemu cpuid code.
> > 
> > > Can a patch be written to set it ?
> > > 
> > Yes.
> 
> Ok I'll try to do that.
> 
Talk to Eduardo since this is related to cpuid configuration and he is
an expert.

> > 
> > > Similarly I noticed that the frequency in the guest was not reflecting the
> > > frequency scaling of the host.
> > > 
> > Not sure what you mean here. Frequency as seen where?
> 
> The frequency seen in the host /proc/cpuinfo and the guest /proc/cpuinfo 
> differs
> when a governor kick the cpu frequency scaling: the guest still show the 
> maximum
> frequency of the cpu.
> 
KVM does not emulate frequency scaling. It does not make sense for a
guest.

> Could this value be reflected dynamically ?
> 
Not sure frequency scaling can be implemented only for read.

--
                        Gleb.