On 05/15/2015 01:49 PM, David Daney wrote:
On 05/14/2015 06:34 PM, Leonid Yegoshin wrote:
SEGBITS default is 40 bits or less, depending from CPU type.
This patch introduces 48bits of application virtual address (SEGBITS)
support.
It is defined only for 16K and 64K pages and is optional (configurable).
Penalty - a small number of additional pages for generic (small)
applications.
But for 64K pages it adds 3rd level of PTE structure, which has a little
impact during software TLB refill.
This patch is needed because MIPS I6XXX and P6XXX cores have 48 bit of
virtual address in each segment (SEGBITS).
Those processors don't require the patch. You wrote the patch to give
a larger VA space at the request of kernel users. So perhaps say:
The patch (optionally) increases the VA space available to userspace
processes from N-bits to 48-bits
... if CPU model supports that
+config 48VMBITS
Should probabaly be called VABITS instead of VMBITS to match the terms
used in the architecture reference manuals, as well as other ports
(ARM64).
Perhaps MIPS_VA_BITS_48
I don't mind here. It can be even called 48SEGBITS or so, to match arch
manual more. MIPS Arch manual never says about VA bits but speaks about
PABITS and SEGBITS.
- Leonid.
