linux-kernel - Re: [PATCH v3 13/34] m68k: Implement the new page table range API

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Date:   Mon, 6 Mar 2023 08:21:44 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Michael Schmitz <schmitzmic@...il.com>
Cc:     Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org
Subject: Re: [PATCH v3 13/34] m68k: Implement the new page table range API

Hi Michael,

On Sun, Mar 5, 2023 at 9:44 PM Michael Schmitz <schmitzmic@...il.com> wrote:
> On 6/03/23 04:28, Matthew Wilcox wrote:
> > On Sun, Mar 05, 2023 at 11:16:13AM +0100, Geert Uytterhoeven wrote:
> >>> +               while (nr--) {
> >>> +                       __asm__ __volatile__("nop\n\t"
> >>> +                                            ".chip 68040\n\t"
> >>> +                                            "cpushp %%bc,(%0)\n\t"
> >>> +                                            ".chip 68k"
> >>> +                                            : : "a" (paddr + nr * PAGE_SIZE));
> >> As gcc (9.5.0) keeps on calculating "paddr + nr * PAGE_SIZE"
> >> inside the loop (albeit using a shift instead of a multiplication),
> >> please use "paddr" here, followed by "paddr += PAGE_SIZE;".
>
> Are we certain that contiguous vaddr always maps to contiguous paddr?

For a general __flush_pages_to_ram() function, that would not be
guaranteed. But as this is meant for folios, it must be true:
https://elixir.bootlin.com/linux/latest/source/include/linux/mm_types.h#L320

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