> -----Original Message----- > From: Peter Zijlstra [mailto:[email protected]] > Sent: Wednesday, July 09, 2014 10:58 AM > To: Liang, Kan > Cc: [email protected]; [email protected]; [email protected] > Subject: Re: [PATCH V4 1/2] perf ignore LBR and extra_regs. > > On Wed, Jul 09, 2014 at 02:32:28PM +0000, Liang, Kan wrote: > > > > > > > On Tue, Jul 08, 2014 at 09:49:40AM -0700, [email protected] 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.
The patch 2 is to handle the case that the administrator can only patch the host. Don't need to force user to upgrade their guest to fix the crash. And ignore the annoying "unhandled...." KVM messages -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
