RE: [PATCH V4 1/2] perf ignore LBR and extra_regs.

[Liang, Kan]

> On Tue, Jul 08, 2014 at 09:49:40AM -0700, kan.liang@xxxxxxxxx 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?

If applying patch 2, the function will return true. The KVM just simply ignore the reads/writes.
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