On Wed, Nov 06, 2024 at 11:07:53AM -0500, Liang, Kan wrote:
> > +#ifndef perf_arch_guest_misc_flags
> > +static inline unsigned long perf_arch_guest_misc_flags(struct pt_regs 
> > *regs)
> > +{
> > +   unsigned long guest_state = perf_guest_state();
> > +
> > +   if (guest_state & PERF_GUEST_USER)
> > +           return PERF_RECORD_MISC_GUEST_USER;
> > +
> > +   if (guest_state & PERF_GUEST_ACTIVE)
> > +           return PERF_RECORD_MISC_GUEST_KERNEL;
> 
> Is there by any chance to add a PERF_GUEST_KERNEL flag in KVM?

Why do we need another flag? As it stands today, the vCPU is either in
user mode or kernel mode.

> The PERF_GUEST_ACTIVE flag check looks really confusing.

Perhaps instead:

static inline unsigned long perf_arch_guest_misc_flags(struct pt_regs *regs)
{
        unsigned long guest_state = perf_guest_state();

        if (!(guest_state & PERF_GUEST_ACTIVE))
                return 0;

        return (guest_state & PERF_GUEST_USER) ? PERF_RECORD_MISC_GUEST_USER :
                                                 PERF_RECORD_MISC_GUEST_KERNEL;
}

-- 
Thanks,
Oliver

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