Messages in this thread | | | Date | Wed, 19 Oct 2022 11:32:25 +0200 | From | "Arnd Bergmann" <> | Subject | Re: [PATCH] ARM: mm: fix no-MMU ZERO_PAGE() implementation |
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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
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