linux-kernel - Re: [PATCH] x86/mce: Fix set_mce

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Message-ID: <CA+55aFxVQqnFVQaCYHbnWnt3kBfVkLWgNvKFkf6qgDWCSDNpEg@mail.gmail.com>
Date:   Thu, 30 Aug 2018 18:29:11 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Tony Luck <tony.luck@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Peter Anvin <hpa@...or.com>,
        Borislav Petkov <bp@...en8.de>,
        linux-edac <linux-edac@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Jiang <dave.jiang@...el.com>
Subject: Re: [PATCH] x86/mce: Fix set_mce_nospec() to avoid #GP fault

On Thu, Aug 30, 2018 at 2:45 PM Tony Luck <tony.luck@...el.com> wrote:
>
> Fix is to move one step at a time. First mark the page not present
> (using the decoy address). Then it is safe to use the actual address
> of the 1:1 mapping to mark it "uc", and finally as present.

Can't we do it in one step, but make sure that he clflush gets the real address?

              Linus