linux-kernel - Re: [PATCH] RDMSR before test_cpu_capacity brings about KVM warning

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Date:	Mon, 17 Aug 2015 13:23:22 +0000
From:	"Han, Huaitong" <huaitong.han@...el.com>
To:	"alexander.shishkin@...ux.intel.com" 
	<alexander.shishkin@...ux.intel.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"a.p.zijlstra@...llo.nl" <a.p.zijlstra@...llo.nl>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"acme@...nel.org" <acme@...nel.org>
Subject: Re: [PATCH] RDMSR before test_cpu_capacity brings about KVM warning

On Mon, 2015-08-17 at 15:04 +0300, Alexander Shishkin wrote:
> Huaitong Han <huaitong.han@...el.com> writes:
> 
> > rdmsrl_safe does not lead to #GP in native kernel although CPU
> > does not support INTEL_PT, but if KVM does not support INTEL_PT,
> > the codes cannot understand MSR_IA32_RTIT_CTL, and the warning
> > is produced.
> 
> "the codes"?
KVM codes. Current KVM does not support Intel_PT. But guest kernel may
readmsr MSR_IA32_RTIT_CTL that KVM cannot understand.
Details from https://bugzilla.kernel.org/show_bug.cgi?id=102651
> 
> > If KVM does not support INTEL_PT, its guest CPUID also does not.
> > So test_cpu_cap is added before RDMSR, and it is more in line with
> > the code style.
> 
> It does make more sense like this, but please improve this commit
> message. And don't forget to include Peter in the loop.
I will update the commit message.
> 
> FWIW,
> 
> Reviewed-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> 
> Regards,
> --
> Alex