linux-kernel - Re: [PATCH 4.9 43/92] x86/pti: Do not enable PTI on CPUs which are not vulnerable to Meltdown

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Message-ID: <CADSoG1tjU2G9FUNOFod4ZsYSw7gOSsza_JWUv5H6pAkbftWywA@mail.gmail.com>
Date:   Tue, 13 Feb 2018 13:34:07 +0000
From:   Nick Lowe <nick.lowe@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        David Woodhouse <dwmw@...zon.co.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...e.de>,
        Dave Hansen <dave.hansen@...el.com>,
        gnomes@...rguk.ukuu.org.uk, ak@...ux.intel.com,
        ashok.raj@...el.com, karahmed@...zon.de, arjan@...ux.intel.com,
        torvalds@...ux-foundation.org, peterz@...radead.org,
        Borislav Petkov <bp@...en8.de>, pbonzini@...hat.com,
        tim.c.chen@...ux.intel.com, gregkh@...ux-foundation.org
Subject: Re: [PATCH 4.9 43/92] x86/pti: Do not enable PTI on CPUs which are
 not vulnerable to Meltdown

Hi,

This does not seem to have subsumed the AMD specific code in

x86/pti: Do not enable PTI on CPUs which are not vulnerable to Meltdown
Commit a8799fd14d9f7f385a5a5c86cde247caf4bb0320

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?h=v4.9.81&id=a8799fd14d9f7f385a5a5c86cde247caf4bb0320

x86/kaiser: Check boottime cmdline params
Commit 8018307a45a90ab2eecfd03d48b7efb31707df37

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/arch/x86/mm/kaiser.c?h=v4.9.75&id=8018307a45a90ab2eecfd03d48b7efb31707df37

Here, we can see:

+skip:
+ if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
+ goto disable;

Refer to 4.9.81's kaiser.c
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/tree/arch/x86/mm/kaiser.c?h=v4.9.81

Also 4.4.115's kaiser.c
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/tree/arch/x86/mm/kaiser.c?h=v4.4.115

Cheers,

Nick