linux-kernel - Re: [PATCH V4 1/2] perf ignore LBR and extra

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Message-ID: <20140709141631.GE9918@twins.programming.kicks-ass.net>
Date:	Wed, 9 Jul 2014 16:16:31 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	kan.liang@...el.com
Cc:	andi@...stfloor.org, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Subject: Re: [PATCH V4 1/2] perf ignore LBR and extra_regs.

On Tue, Jul 08, 2014 at 09:49:40AM -0700, kan.liang@...el.com wrote:
> +/*
> + * Under certain circumstances, access certain MSR may cause #GP.
> + * The function tests if the input MSR can be safely accessed.
> + */
> +static inline bool check_msr(unsigned long msr)
> +{
> +	u64 value;
> +
> +	if (rdmsrl_safe(msr, &value) < 0)
> +		return false;
> +	if (wrmsrl_safe(msr, value) < 0)
> +		return false;
> +	return true;
> +}

What does this thing return after patch 2? does the write still fault or
will KVM silently take writes too?

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