linux-kernel - Re: [PATCH 2/4] mm: rmap: Allow platforms without mm

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Message-ID: <YsfqjsntneiX0xYE@hirez.programming.kicks-ass.net>
Date:   Fri, 8 Jul 2022 10:27:58 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Nadav Amit <namit@...are.com>
Cc:     Barry Song <21cnbao@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Jonathan Corbet <corbet@....net>,
        "darren@...amperecomputing.com" <darren@...amperecomputing.com>,
        "guojian@...o.com" <guojian@...o.com>,
        "huzhanyuan@...o.com" <huzhanyuan@...o.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "lipeifeng@...o.com" <lipeifeng@...o.com>,
        "mgorman@...e.de" <mgorman@...e.de>,
        "realmz6@...il.com" <realmz6@...il.com>,
        "v-songbaohua@...o.com" <v-songbaohua@...o.com>,
        "will@...nel.org" <will@...nel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "yangyicong@...ilicon.com" <yangyicong@...ilicon.com>,
        "zhangshiming@...o.com" <zhangshiming@...o.com>
Subject: Re: [PATCH 2/4] mm: rmap: Allow platforms without mm_cpumask to
 defer TLB flush

On Fri, Jul 08, 2022 at 08:08:45AM +0000, Nadav Amit wrote:

> Is it really only x86 that has mm_cpumask()?

Unlikely, everybody who needs to IPI (eg. doesn't have broadcast
invalidate) has benefit to track this mask more accurately.

The below greps for clearing CPUs in the mask and ought to be a fair
indicator:

$ git grep -l "cpumask_clear_cpu.*mm_cpumask" arch/
arch/arm/include/asm/mmu_context.h
arch/loongarch/include/asm/mmu_context.h
arch/loongarch/mm/tlb.c
arch/mips/include/asm/mmu_context.h
arch/openrisc/mm/tlb.c
arch/powerpc/include/asm/book3s/64/mmu.h
arch/powerpc/mm/book3s64/radix_tlb.c
arch/riscv/mm/context.c
arch/s390/kernel/smp.c
arch/um/include/asm/mmu_context.h
arch/x86/mm/tlb.c