linux-kernel - Re: [PATCH v9 02/29] x86/boot: Relocate definition of the initial state of CR0

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Date:   Thu, 26 Oct 2017 00:51:25 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Brian Gerst <brgerst@...il.com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Liang Z Li <liang.z.li@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Huang Rui <ray.huang@....com>, Jiri Slaby <jslaby@...e.cz>,
        Jonathan Corbet <corbet@....net>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Chen Yucong <slaoub@...il.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Shuah Khan <shuah@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        X86 ML <x86@...nel.org>,
        "Neri, Ricardo" <ricardo.neri@...el.com>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...el.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH v9 02/29] x86/boot: Relocate definition of the initial
 state of CR0

On Tue, Oct 3, 2017 at 8:54 PM, Ricardo Neri
<ricardo.neri-calderon@...ux.intel.com> wrote:
> Both head_32.S and head_64.S utilize the same value to initialize the
> control register CR0. Also, other parts of the kernel might want to access
> this initial definition (e.g., emulation code for User-Mode Instruction
> Prevention uses this state to provide a sane dummy value for CR0 when
> emulating the smsw instruction). Thus, relocate this definition to a
> header file from which it can be conveniently accessed.

Reviewed-by: Andy Lutomirski <luto@...nel.org>

with the slight caveat that I think it might be a wee bit better if
UMIP emulation used a separate define UMIP_REPORTED_CR0.