linux-kernel - Re: [PATCH v2 1/2] mm: Introduce flush_cache_vmap

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Date:   Wed, 13 Dec 2023 09:36:15 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Alexandre Ghiti <alexghiti@...osinc.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Arnd Bergmann <arnd@...db.de>, Dennis Zhou <dennis@...nel.org>,
        Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-arch@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v2 1/2] mm: Introduce flush_cache_vmap_early()

On Tue, Dec 12, 2023 at 10:36 PM Alexandre Ghiti <alexghiti@...osinc.com> wrote:
> The pcpu setup when using the page allocator sets up a new vmalloc
> mapping very early in the boot process, so early that it cannot use the
> flush_cache_vmap() function which may depend on structures not yet
> initialized (for example in riscv, we currently send an IPI to flush
> other cpus TLB).
>
> But on some architectures, we must call flush_cache_vmap(): for example,
> in riscv, some uarchs can cache invalid TLB entries so we need to flush
> the new established mapping to avoid taking an exception.
>
> So fix this by introducing a new function flush_cache_vmap_early() which
> is called right after setting the new page table entry and before
> accessing this new mapping. This new function implements a local flush
> tlb on riscv and is no-op for other architectures (same as today).
>
> Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>

>  arch/m68k/include/asm/cacheflush_mm.h  | 1 +

Acked-by: Geert Uytterhoeven <geert@...ux-m68k.org>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds