Subject: Re: [PATCH v7 4/5] x86: perf: Refactor misc flag assignments

From: Peter Zijlstra <[email-masked]>
Date: Fri, 8 Nov 2024 20:32:04 +0100

On Fri, Nov 08, 2024 at 08:20:44PM +0100, Peter Zijlstra wrote:

> Isn't the below more or less what you want?
> 
> static unsigned long misc_flags(struct pt_regs *regs)
> {
> 	unsigned long flags = 0;
> 
> 	if (regs->flags & PERF_EFLAGS_EXACT)
> 		flags |= PERF_RECORD_MISC_EXACT_IP;
> 
> 	return flags;
> }
> 
> static unsigned long native_flags(struct pt_regs *regs)
> {
> 	unsigned long flags = 0;
> 
> 	if (user_mode(regs))
> 		flags |= PERF_RECORD_MISC_USER;
> 	else
> 		flags |= PERF_RECORD_MISC_KERNEL;
> 
> 	return flags;
> }
> 
> static unsigned long guest_flags(struct pt_regs *regs)
> {
> 	unsigned long guest_state = perf_guest_state();
> 	unsigned long flags = 0;
> 
> 	if (guest_state & PERF_GUEST_ACTIVE) {
> 		if (guest_state & PERF_GUEST_USER)
> 			flags |= PERF_RECORD_MISC_GUEST_USER;
> 		else
> 			flags |= PERF_RECORD_MISC_GUEST_KERNEL;
> 	}
> 
> 	return flags;
> }
> 
> unsigned long perf_arch_guest_misc_flags(struct pt_regs *regs)
> {
> 	unsigned long flags;
> 
> 	flags = misc_flags(regs);
> 	flags |= guest_flags(regs);
> 
> 	return flags;
> }
> 
> unsigned long perf_arch_misc_flags(struct pt_regs *regs)
> {
> 	unsigned long flags;
> 	unsigned long guest;
> 
> 	flags = misc_flags(regs);
> 	guest = guest_flags(regs);
> 	if (guest)
> 		flags |= guest;
> 	else
> 		flags |= native_flags(regs);
> 
> 	return flags;
> }

This last can be written more concise:

unsigned long perf_arch_misc_flags(struct pt_regs *regs)
{
	unsigned long flags;

	flags = guest_flags(regs);
	if (!flags)
		flags |= native_flags(regs);

	flgs |= misc_flags(regs);

	return flags;
}