linux-kernel - Re: TLB flushes on fixmap changes

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Message-ID: <20180826221541.GB30765@bombadil.infradead.org>
Date:   Sun, 26 Aug 2018 15:15:41 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...capital.net>,
        Andy Lutomirski <luto@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Nadav Amit <nadav.amit@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jiri Kosina <jkosina@...e.cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will.deacon@....com>,
        Benjamin Herrenschmidt <benh@....ibm.com>,
        Nick Piggin <npiggin@...il.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Rik van Riel <riel@...riel.com>,
        Jann Horn <jannh@...gle.com>,
        Adin Scannell <ascannell@...gle.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        David Miller <davem@...emloft.net>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: TLB flushes on fixmap changes

On Sun, Aug 26, 2018 at 03:03:59PM -0700, Kees Cook wrote:
> I thought the point was that the implementation I suggested was
> NMI-proof? (And in reading Documentation/preempt-locking.txt it sounds
> like disabling interrupts is redundant to preempt_disable()? But I
> don't understand how; it looks like the preempt stuff is advisory?)

Oter way round; disabling interrupts implicitly disables preemption