linux-kernel - Re: [PATCH 2/7] x86/enter: MACROS to set/clear IBRS

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Message-ID: <CALCETrVY+hu7WnhW=RoVFD8-0LE7E3=_pO6ZQWkyobv1F7H=QA@mail.gmail.com>
Date:   Thu, 4 Jan 2018 20:54:10 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Tim Chen <tim.c.chen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/7] x86/enter: MACROS to set/clear IBRS

On Thu, Jan 4, 2018 at 2:23 PM, Dave Hansen <dave.hansen@...el.com> wrote:
> On 01/04/2018 02:21 PM, Tim Chen wrote:
>>> Does this really have to live outside of arch/x86/entry/ ?
>>>
>> There are some inline C routines later in this file
>> that will be needed by other functions.  Want to consolidate
>> them in the same file.
>
> We could put all of the assembly into calling.h along with the PTI
> assembly.  Seems as sane a place as anywhere else to put it.
>

We should also stop thinking that NMI is at all special.  All the
paranoid entry paths + NMI should just save and restore it, just like
CR3.  Otherwise we get nasty corner cases with MCE, kprobes, etc.