Subject: Re: [PATCH v6 4/5] x86: perf: Refactor misc flag assignments

From: Oliver Upton <[email-masked]>
Date: Wed, 6 Nov 2024 12:02:02 -0800

On Wed, Nov 06, 2024 at 11:03:10AM -0500, Liang, Kan wrote:
> > +static unsigned long common_misc_flags(struct pt_regs *regs)
> > +{
> > +	if (regs->flags & PERF_EFLAGS_EXACT)
> > +		return PERF_RECORD_MISC_EXACT_IP;
> > +
> > +	return 0;
> > +}
> > +
> > +unsigned long perf_arch_guest_misc_flags(struct pt_regs *regs)
> > +{
> > +	unsigned long guest_state = perf_guest_state();
> > +	unsigned long flags = common_misc_flags(regs);
> > +
> > +	if (guest_state & PERF_GUEST_USER)
> > +		flags |= PERF_RECORD_MISC_GUEST_USER;
> > +	else if (guest_state & PERF_GUEST_ACTIVE)
> > +		flags |= PERF_RECORD_MISC_GUEST_KERNEL;
> > +
> 
> The logic of setting the GUEST_KERNEL flag is implicitly changed here.
> 
> For the current code, the GUEST_KERNEL flag is set for !PERF_GUEST_USER,
> which include both guest_in_kernel and guest_in_NMI.

Where is the "guest_in_NMI" state coming from? KVM only reports user v.
kernel mode.

-- 
Thanks
Oliver