Messages in this thread | | | Date | Wed, 9 Jul 2014 16:58:09 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH V4 1/2] perf ignore LBR and extra_regs. |
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On Wed, Jul 09, 2014 at 02:32:28PM +0000, Liang, Kan wrote: > > > > On Tue, Jul 08, 2014 at 09:49:40AM -0700, kan.liang@intel.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? > > If applying patch 2, the function will return true. The KVM just simply ignore the reads/writes.
OK, then that's broken too. We want a function to return false for any malfunctioning MSR, ignoring writes and returning 0s is not proper functioning. [unhandled content-type:application/pgp-signature] | |