Re: [PATCH v2] sparc64: Add support for Application Data Integrity (ADI)

[Rob Gardner]

On 03/07/2016 01:33 PM, Khalid Aziz wrote:
> That is a possibility but limited in scope. An address range covered 
> by a single TTE can have large number of tags. Version tags are set on 
> cacheline. In extreme case, one could set a tag for each set of 
> 64-bytes in a page. Also tags are set completely in userspace and no 
> transition occurs to kernel space, so kernel has no idea of what tags 
> have been set.

  ...
> I have not found a way to query the MMU on tags.

To query the tag for a cache line, you just read it back with ldxa and 
ASI_MCD_PRIMARY (ie, asi 0x90), basically the same way you stored the 
tag in the first place.

Rob