Messages in this thread | | | Subject | Re: [RFC PATCH 1/2] mm,drm/ttm: Block fast GUP to TTM huge pages | From | Dave Hansen <> | Date | Wed, 24 Mar 2021 09:34:48 -0700 |
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On 3/24/21 3:05 AM, Thomas Hellström (Intel) wrote: > Yes, I agree. Seems like the special (SW1) is available also for huge > page table entries on x86 AFAICT, although just not implemented. > Otherwise the SW bits appear completely used up.
Although the _PAGE_BIT_SOFTW* bits are used up, there's plenty of room in the hardware PTEs. Bits 52->58 are software-available, and we're only using 58 at the moment.
We also have not been careful at *all* about how _PAGE_BIT_SOFTW* are used. It's quite possible we can encode another use even in the existing bits.
Personally, I'd just try:
#define _PAGE_BIT_SOFTW5 57 /* available for programmer */
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