Re: [RFC PATCH v3] sparc64: Add support for Application Data Integrity (ADI)

[Dave Hansen]

On 01/04/2017 04:05 PM, Rob Gardner wrote:
>> What if two different small pages have different tags and khugepaged
>> comes along and tries to collapse them?  Will the page be split if a
>> user attempts to set two different tags inside two different small-page
>> portions of a single THP?
> 
> The MCD tags operate at a resolution of cache lines (64 bytes). Page
> sizes don't matter except that each virtual page must have a bit set in
> its TTE to allow MCD to be enabled on the page. Any page can have many
> different tags, one for each cache line.

Is an "MCD tag" the same thing as a "ADI version tag"?

The thing that confused me here is that we're taking an entire page of
"ADI version tags" and stuffing them into a swap pte (in
set_swp_pte_at()).  Do we somehow have enough space in a swap pte on
sparc to fit PAGE_SIZE/64 "ADI version tag"s in there?