mips pmap patch

[Jayachandran C.]

On Mon, Aug 27, 2012 at 9:54 AM, Alan Cox <alc at rice.edu> wrote:
> Could you please test the attached patch?  For a change, this patch is an
> optimization (as opposed to a bug fix).  It carves off a third high-order
> bit from the PTE in order to implement another software flag.  For 64-bit
> systems, this bit was previously unused.  For 32-bit systems, this patch
> effectively reduces the size of the PTE's page frame number (PFN) field by 1
> bit.  However, the PFN still has more than enough bits to support the 32-bit
> vm_paddr_t.
>
> This patch needs both 32-bit and 64-bit testing.  I'm fairly confident of
> the correctness of the 64-bit case, but less so of the 32-bit case.

Tested this on both 32 and 64 bit configuration on XLP and no problems
were seen.

> Going forward, I expect to claim a fourth bit from the PTE in order to
> implement a proper access bit emulation.

Regards,
JC