x86/mm: Always allocate a whole page for PAE PGDs

Browse source

A hardware PAE PGD is only 32 bytes. A PGD is PAGE_SIZE in the other
paging modes. But for reasons*, the kernel _sometimes_ allocates a
whole page even though it only ever uses 32 bytes.

Make PAE less weird. Just allocate a page like the other paging modes.
This was already being done for PTI (and Xen in the past) and nobody
screamed that loudly about it so it can't be that bad.

 * The original reason for PAGE_SIZE allocations for the PAE PGDs was
   Xen's need to detect page table writes. But 32-bit PTI forced it too
   for reasons I'm unclear about.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20250414173234.D34F0C3E%40davehans-spike.ostc.intel.com

...

This commit is contained in:

Dave Hansen 2025-04-14 10:32:34 -07:00

parent 35c3151a98

commit 780f97e309

1 changed files with 4 additions and 58 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

62

arch/x86/mm/pgtable.c

View file