On 12/20/24 02:58, Kevin Brodsky wrote: >> One super tiny nit is that the PAE pgd _can_ be allocated using >> __get_free_pages(). It was originally there for Xen, but I think it's >> being used for PTI only at this point and the comments are wrong-ish. >> >> I kinda think we should just get rid of the 32-bit kmem_cache entirely. > That would certainly simplify things on the x86 side! I'm not at all > familiar with that code though, would you be happy with providing a > patch? I could add it to this series if that's convenient. I hacked this together yesterday: > https://git.kernel.org/pub/scm/linux/kernel/git/daveh/devel.git/log/?h=simplify-pae-20241220 It definitely needs some more work. I'm particularly still puzzling about why SHARED_KERNEL_PMD is used both as a trigger for 32b vs. PAGE_SIZE PAE pgd allocations _and_ for the actual PMD sharing. Xen definitely needed the whole page behavior but I'm not sure why PTI did. Either way, that series should make the PAE PGDs a _bit_ less weird at the cost of an extra ~2 pages per process for folks who are running 32-bit PAE kernels with PTI disabled. But I think the diffstat is worth it: 5 files changed, 16 insertions(+), 96 deletions(-)
