On 25 November 2024 19:13:02 GMT, Dave Hansen <dave.hansen@xxxxxxxxx> wrote: >On 11/25/24 10:53, David Woodhouse wrote: >>> I think we have a lot of software-available space in the page table >>> pointer entries. What would folks think if we set a special bit in those >>> p4d entries that said: >>> >>> "I don't need to be propagated to >>> the user portion of the page tables." >>> >>> It would obviously get set in this code that you're trying to fix. It >>> might _also_ be able to be set in in "_USR", like here: >>> >>> #define _KERNPG_TABLE_NOENC (__PP|__RW| 0|___A| 0|___D| 0| 0) >>> #define _PAGE_TABLE_NOENC (__PP|__RW|_USR|___A| 0|___D| 0| 0) >>> >>> like: >>> >>> #define _USR _PAGE_USER|_PAGE_SW_WHATEVER >> In fact, do we even need a separate bit? Any PTE without the _PAGE_USER >> bit set clearly doesn't need to be mirrored into the user page >> tables...? > >I can't think of any exceptions where this would break off the top of my >head. It seems too simple to work. ;) I'll throw something together and see if it explodes.
