linux-kernel - Re: [RESEND PATCH 1/3] x86: Adding structs to reflect cpuid fields

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Message-ID: <20140917152221.GF5358@nazgul.tnic>
Date:	Wed, 17 Sep 2014 17:22:21 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Radim Krčmář <rkrcmar@...hat.com>
Cc:	Nadav Amit <namit@...technion.ac.il>,
	Ingo Molnar <mingo@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	the arch/x86 maintainers <x86@...nel.org>,
	kvm <kvm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [RESEND PATCH 1/3] x86: Adding structs to reflect cpuid fields

On Wed, Sep 17, 2014 at 05:04:33PM +0200, Radim Krčmář wrote:
> which would result in a similar if-else hack
> 
>   if (family > X)
>   	ebx.split.max_monitor_line_size_after_family_X = 0
>   else
>   	ebx.split.max_monitor_line_size = 0
> 
> other options are
>   ebx.split.after_family_X.max_monitor_line_size
> or even
>   ebx.split.max_monitor_line_size.after_family_X

And how is that better than simply doing

	cpuid = cpuid_ebx(5);

	if (family > X)
		max_monitor_line_size = cpuid & MASK_FAM_X;
	else
		max_monitor_line_size = cpuid & MASK_BEFORE_FAM_X;

?

With proper variable naming all is perfectly clear, readable
and simple. You don't need to open even the CPUID manual - the
variable tells you you're getting the max monitor line size -
"ebx.split.max_monitor_line_size_after_family_X" needs me to parse it
with my eyes first.

-- 
Regards/Gruss,
    Boris.
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