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

[Rob Gardner]

On 01/04/2017 04:01 PM, Dave Hansen wrote:
> On 01/04/2017 03:58 PM, Khalid Aziz wrote:
> > > How does this all work with large pages?
> > It works with large pages the same way as normal sized pages. The TTE
> > for a large page also will have the mcd bit set in it and tags are set
> > and referenced the same way.
> But does the user setting the tags need to know what the page size is?
>
> 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.

Rob