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Date: Mon, 26 Aug 2013 17:33:20 +0300
From: Gleb Natapov <gleb@redhat.com>
Message-ID: <20130826143320.GA22899@redhat.com>
References: <20130813181713.GA5204@irqsave.net>
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Subject: Re: [Qemu-devel] KVM guest cpu L3 cache and cpufreq
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To: =?utf-8?Q?Beno=C3=AEt?= Canet <benoit.canet@irqsave.net>
Cc: pbonzini@redhat.com, qemu-devel@nongnu.org, Eduardo Habkost <ehabkost@redhat.com>

On Mon, Aug 26, 2013 at 02:49:41PM +0200, Beno=C3=AEt Canet wrote:
>=20
> Hi,
>=20
> Thanks for the answer.
>=20
> > On Tue, Aug 13, 2013 at 08:17:13PM +0200, Beno=C3=AEt Canet wrote:
> > >=20
> > > Hi,
> > >=20
> > > I noticed that the l3 cache size of a guest /proc/cpuinfo is not the =
same as
> > > the l3 cache size of the host.
> > >=20
> > > I did not found any references to this in the qemu and KVM code.
> > >=20
> > > Is the size of the guest L3 cache fixed in hardware ?
> > >=20
> > No, it is hardcoded somewhere in qemu cpuid code.
> >=20
> > > Can a patch be written to set it ?
> > >=20
> > Yes.
>=20
> Ok I'll try to do that.
>=20
Talk to Eduardo since this is related to cpuid configuration and he is
an expert.

> >=20
> > > Similarly I noticed that the frequency in the guest was not reflectin=
g the
> > > frequency scaling of the host.
> > >=20
> > Not sure what you mean here. Frequency as seen where?
>=20
> 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.
>=20
KVM does not emulate frequency scaling. It does not make sense for a
guest.

> Could this value be reflected dynamically ?
>=20
Not sure frequency scaling can be implemented only for read.

--
			Gleb.