Messages in this thread | | | Subject | Re: [RFC PATCH 1/2] mm,drm/ttm: Block fast GUP to TTM huge pages | From | Thomas Hellström (Intel) <> | Date | Wed, 24 Mar 2021 21:22:16 +0100 |
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On 3/24/21 5:34 PM, Dave Hansen wrote: > 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 */ > OK, I'll follow your advise here. FWIW I grepped for SW1 and it seems used in a selftest, but only for PTEs AFAICT.
Oh, and we don't care about 32-bit much anymore?
/Thomas
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