linux-kernel - Re: TLB flushes on fixmap changes

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Message-Id: <823D916E-4056-4A36-BDD8-0FB682A8DCAE@gmail.com>
Date:   Mon, 27 Aug 2018 12:10:34 -0700
From:   Nadav Amit <nadav.amit@...il.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Kees Cook <keescook@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jiri Kosina <jkosina@...e.cz>,
        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

at 11:58 AM, Andy Lutomirski <luto@...nel.org> wrote:

> On Mon, Aug 27, 2018 at 11:54 AM, Nadav Amit <nadav.amit@...il.com> wrote:
>>> On Mon, Aug 27, 2018 at 10:34 AM, Nadav Amit <nadav.amit@...il.com> wrote:
>>> What do you all think?
>> 
>> I agree in general. But I think that current->mm would need to be loaded, as
>> otherwise I am afraid it would break switch_mm_irqs_off().
> 
> What breaks?

Actually nothing. I just saw the IBPB stuff regarding tsk, but it should not
matter.