linux-kernel - Re: [PATCH V2 5/5] ara virt interface of perf to support kvm guest os statistics collection in guest os

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Message-Id: <1277176554.2096.654.camel@ymzhang.sh.intel.com>
Date:	Tue, 22 Jun 2010 11:15:54 +0800
From:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, kvm@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Fr??d??ric Weisbecker <fweisbec@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Lin Ming <ming.m.lin@...el.com>,
	Sheng Yang <sheng@...ux.intel.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	oerg Roedel <joro@...tes.org>,
	Jes Sorensen <Jes.Sorensen@...hat.com>,
	Gleb Natapov <gleb@...hat.com>,
	Zachary Amsden <zamsden@...hat.com>, zhiteng.huang@...el.com,
	tim.c.chen@...el.com, Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH V2 5/5] ara virt interface of perf to support kvm guest
 os statistics collection in guest os

On Mon, 2010-06-21 at 15:37 +0300, Avi Kivity wrote:
> On 06/21/2010 12:31 PM, Zhang, Yanmin wrote:
> > The 5th patch is applied to the latest qemu-kvm tree.
> >
> > --- qemu-kvm_0621/target-i386/kvm.c	2010-06-21 11:00:29.000000000 +0800
> > +++ qemu-kvm_0621_perf/target-i386/kvm.c	2010-06-21 13:00:14.136999850 +0800
> > @@ -150,6 +150,9 @@ struct kvm_para_features {
> >   #ifdef KVM_CAP_PV_MMU
> >           { KVM_CAP_PV_MMU, KVM_FEATURE_MMU_OP },
> >   #endif
> > +#ifdef KVM_CAP_PV_PERF
> > +        { KVM_CAP_PV_PERF, KVM_FEATURE_PV_PERF },
> > +#endif
> >           { -1, -1 }
> >   };
> >
> >    
> 
> 
> Not really necessary any more - if you expose the cpuid bit via 
> KVM_GET_SUPPORTED_CPUID2 then 'qemu -cpu host' will automatically enable it.
> 
> On the other hand, do update target-i386/cpuid.c:kvm_feature_name so 
> people can enable the feature using qemu -cpu ...,+kvmperf.
Thanks for the good pointer. I will change it.

Avi,

Thanks for your wonderful comments. I will fix all in the patches.
As for the live migration, I need check it carefully. If you could
provide some suggestions on it, especially about how/when to save all perf_events
and restore all pref_events, that would be very helpful.

Yanmin


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