linux-kernel - Re: [RFC 11/20] mm/tlb: remove arch-specific tlb_start/end

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Date:   Tue, 2 Feb 2021 12:04:09 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Nadav Amit <namit@...are.com>
Cc:     Nicholas Piggin <npiggin@...il.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "linux-csky@...r.kernel.org" <linux-csky@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>, X86 ML <x86@...nel.org>,
        Yu Zhao <yuzhao@...gle.com>
Subject: Re: [RFC 11/20] mm/tlb: remove arch-specific tlb_start/end_vma()

On Tue, Feb 02, 2021 at 09:54:36AM +0000, Nadav Amit wrote:
> > On Feb 2, 2021, at 1:31 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> > 
> > On Tue, Feb 02, 2021 at 07:20:55AM +0000, Nadav Amit wrote:
> >> Arm does not define tlb_end_vma, and consequently it flushes the TLB after
> >> each VMA. I suspect it is not intentional.
> > 
> > ARM is one of those that look at the VM_EXEC bit to explicitly flush
> > ITLB IIRC, so it has to.
> 
> Hmm… I don’t think Arm is doing that. At least arm64 does not use the
> default tlb_flush(), and it does not seem to consider VM_EXEC (at least in
> this path):
> 

ARM != ARM64. ARM certainly does, but you're right, I don't think ARM64
does this.