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Subject: Re: TLB flushes on fixmap changes
From:   Nadav Amit <nadav.amit@gmail.com>
In-Reply-To: <CALCETrUoNdwDuNSHb3haw9-fYk+sNC_M4r+5EMVVzJ8HWeSsOQ@mail.gmail.com>
Date:   Mon, 27 Aug 2018 12:10:34 -0700
Cc:     Masami Hiramatsu <mhiramat@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Kees Cook <keescook@chromium.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Jiri Kosina <jkosina@suse.cz>,
        Will Deacon <will.deacon@arm.com>,
        Benjamin Herrenschmidt <benh@au1.ibm.com>,
        Nick Piggin <npiggin@gmail.com>,
        the arch/x86 maintainers <x86@kernel.org>,
        Borislav Petkov <bp@alien8.de>,
        Rik van Riel <riel@surriel.com>,
        Jann Horn <jannh@google.com>,
        Adin Scannell <ascannell@google.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        David Miller <davem@davemloft.net>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Michael Ellerman <mpe@ellerman.id.au>
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To:     Andy Lutomirski <luto@kernel.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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

> On Mon, Aug 27, 2018 at 11:54 AM, Nadav Amit <nadav.amit@gmail.com> =
wrote:
>>> On Mon, Aug 27, 2018 at 10:34 AM, Nadav Amit <nadav.amit@gmail.com> =
wrote:
>>> What do you all think?
>>=20
>> 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().
>=20
> What breaks?

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