linux-kernel - Re: flush_kernel_dcache

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Message-ID: <CAHk-=whd0GaAH7gHuEiuKjOeD6JGKY1q5ydG1TCKjVBFNBUEJA@mail.gmail.com>
Date:   Mon, 12 Jul 2021 12:24:11 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Russell King <linux@...linux.org.uk>,
        Guo Ren <guoren@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Nick Hu <nickhu@...estech.com>,
        Greentime Hu <green.hu@...il.com>,
        Vincent Chen <deanbo422@...il.com>,
        Helge Deller <deller@....de>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        Geoff Levand <geoff@...radead.org>,
        Paul Cercueil <paul@...pouillou.net>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Alex Shi <alexs@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-csky@...r.kernel.org,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@...r.kernel.org>,
        linux-parisc@...r.kernel.org,
        Linux-sh list <linux-sh@...r.kernel.org>,
        linux-mmc@...r.kernel.org, linux-scsi <linux-scsi@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>
Subject: Re: flush_kernel_dcache_page fixes and removal

On Sun, Jul 11, 2021 at 11:09 PM Christoph Hellwig <hch@....de> wrote:
>
> I think we should just remove it and eat the very minor overhead in
> exec rather than confusing poor driver writers.

Ack.

I think architectures that have virtual caches might want to think
about this patch a bit more, but on the whole I can't argue against
the "it's badly documented and misused".

No sane architecture will care, since dcache will be coherent (there
are more issues on the I$ side, but that's a different issue)

              Linus