linux-kernel - Re: [RFC, PATCHv1 15/28] x86: detect 5-level paging support

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Message-ID: <20161215192017.GP8388@tassilo.jf.intel.com>
Date:   Thu, 15 Dec 2016 11:20:17 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     hpa@...or.com, Linus Torvalds <torvalds@...ux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Arnd Bergmann <arnd@...db.de>,
        Dave Hansen <dave.hansen@...el.com>,
        Andy Lutomirski <luto@...capital.net>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC, PATCHv1 15/28] x86: detect 5-level paging support


The code is not calling CPUID in any performance critical path, only
at initialization. So any discussion about saving a few instructions
is a complete waste of time.

-Andi