On 03/07/2016 10:39 AM, Khalid Aziz wrote:

On 03/07/2016 11:12 AM, Dave Hansen wrote:

quoted

On 03/07/2016 09:53 AM, Andy Lutomirski wrote:

quoted

Also, what am I missing?  Tying these tags to the physical page seems
like a poor design to me.  This seems really awkward to use.

Yeah, can you describe the structures that store these things? Surely
the hardware has some kind of lookup tables for them and stores them in
memory _somewhere_.

Version tags are tied to virtual addresses, not physical pages.

Where exactly are the tags stored is part of processor architecture 
and I am not privy to that. MMU stores these lookup tables somewhere 
and uses it to authenticate access to virtual addresses. It really is 
irrelevant to kernel how MMU implements access controls as long as we 
have access to the knowledge of how to use it.

The tags are stored in physical memory, and you can write a tag directly 
to that memory via stxa with ASI_MCD_REAL and completely bypass the MMU. 
When you do that, the tag will still be seen by any virtual address that 
maps to that physical address.

Rob



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