From: "Arnd Bergmann" <arnd@arndb.de>
To: "Russell King" <linux@armlinux.org.uk>
Cc: "Giulio Benetti" <giulio.benetti@benettiengineering.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
"Anshuman Khandual" <anshuman.khandual@arm.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Kefeng Wang" <wangkefeng.wang@huawei.com>,
"Will Deacon" <will@kernel.org>
Subject: Re: [PATCH] ARM: mm: fix no-MMU ZERO_PAGE() implementation
Date: Wed, 19 Oct 2022 11:32:25 +0200 [thread overview]
Message-ID: <6d454246-578f-4a25-bddf-2f68f32d2213@app.fastmail.com> (raw)
In-Reply-To: <Y0++52o7QSaDvqpM@shell.armlinux.org.uk>
On Wed, Oct 19, 2022, at 11:09, Russell King (Oracle) wrote:
> When the only users in the kernel _were_ ZERO_PAGE() for this, which
> is defined to return a struct page pointer, there was no need to make
> "empty_zero_page" anything but a struct page pointer, rather than a
> runtime translation from an address to a struct page.
Fair enough.
> IMHO, we should _not_ be exposing empty_zero_page to devices - we
> certainly do not want the DMA API performing cache maintenance on
> this page since the primary purpose of this page is to fill in
> userspace BSS pages that have not been written.
It should be easy enough to not expose it by renaming the
symbol to something other than empty_zero_page. That way,
any incorrect users that may come up in the future would
at least result in a build failure instead of runtime
data corruption.
> So, the only one that needs fixing is the SPI usage, which IMHO
> is wrong. ARM being different finds what I consider a driver bug.
> Good for 32-bit ARM. :)
The SPI driver is powerpc specific, so it's also not going to
get hit.
Arnd
next prev parent reply other threads:[~2022-10-19 11:29 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-17 23:37 [PATCH] ARM: mm: fix no-MMU ZERO_PAGE() implementation Giulio Benetti
2022-10-18 7:03 ` Arnd Bergmann
2022-10-18 17:44 ` Giulio Benetti
2022-10-18 18:35 ` Arnd Bergmann
2022-10-18 22:32 ` Giulio Benetti
2022-10-19 7:00 ` Arnd Bergmann
2022-10-19 16:37 ` Giulio Benetti
2022-10-19 9:09 ` Russell King (Oracle)
2022-10-19 9:32 ` Arnd Bergmann [this message]
2022-10-19 17:07 ` Giulio Benetti
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