[RFC PATCH 1/2] mm,drm/ttm: Block fast GUP to TTM huge pages

[Dave Hansen]

On 3/24/21 1:22 PM, Thomas Hellström (Intel) wrote:
>> 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?

On x86, we have 64-bit PTEs when running 32-bit kernels if PAE is
enabled.  IOW, we can handle the majority of 32-bit CPUs out there.

But, yeah, we don't care about 32-bit. :)