Re: KVM PMU virtualization

Zhang, Yanmin
2010-03-04T00:50:20Z

On Wed, 2010-03-03 at 11:13 +0100, Peter Zijlstra wrote:
> On Wed, 2010-03-03 at 17:27 +0800, Zhang, Yanmin wrote:
> > +static inline u64 perf_instruction_pointer(struct pt_regs *regs)
> > +{
> > + u64 ip;
> > + ip = percpu_read(perf_virt_ip.ip);
> > + if (!ip)
> > + ip = instruction_pointer(regs);
> > + else
> > + perf_reset_virt_ip();
> > + return ip;
> > +}
> > +
> > +static inline unsigned int perf_misc_flags(struct pt_regs *regs)
> > +{
> > + if (percpu_read(perf_virt_ip.ip)) {
> > + return percpu_read(perf_virt_ip.user_mode) ?
> > + PERF_RECORD_MISC_GUEST_USER :
> > + PERF_RECORD_MISC_GUEST_KERNEL;
> > + } else
> > + return user_mode(regs) ? PERF_RECORD_MISC_USER :
> > + PERF_RECORD_MISC_KERNEL;
> > +}
>
> This codes in the assumption that perf_misc_flags() must only be called
> before perf_instruction_pointer(), which is currently true, but you
> might want to put a comment near to remind us of this.
I will change the logic with a clear reset operation in caller.