On 16/04/2021 11:38, Christophe Leroy wrote:
Le 16/04/2021 à 11:28, Steven Price a écrit :
On 15/04/2021 18:18, Christophe Leroy wrote:
To be honest I don't fully understand why powerpc requires the page_size - it appears to be using it purely to find "holes" in the calls to note_page(), but I haven't worked out why such holes would occur.
I was indeed introduced for KASAN. We have a first commit https://github.com/torvalds/linux/commit/cabe8138 which uses page size to detect whether it is a KASAN like stuff.
Then came https://github.com/torvalds/linux/commit/b00ff6d8c as a fix. I can't remember what the problem was exactly, something around the use of hugepages for kernel memory, came as part of the series https://patchwork.ozlabs.org/project/linuxppc-dev/cover/cover.1589866984.git.christophe.leroy@xxxxxxxxxx/
Ah, that's useful context. So it looks like powerpc took a different route to reducing the KASAN output to x86.
Given the generic ptdump code has handling for KASAN already it should be possible to drop that from the powerpc arch code, which I think means we don't actually need to provide page size to notepage(). Hopefully that means more code to delete ;)