[PATCH] Use 1TB segments

[Paul Mackerras]

Olof Johansson writes:

> > This makes the kernel use 1TB segments for all kernel mappings and for
> > user addresses of 1TB and above, on machines which support them
> > (currently POWER5+ and POWER6).
> 
> PA6T supports them as well :)

In the patch, we don't actually hard-code the CPU_FTR_1T_SEGMENT bit
in the cputable entry for any processor; instead we look in the
ibm,processor-segment-sizes property in the cpu node(s) in the device
tree.  Do you want us to add the CPU_FTR_1T_SEGMENT bit to the
cputable entry for the PA6T, or will your firmware gives the
ibm,processor-segment-sizes property in the device tree?

> Wouldn't it be possible to stick with 1TB segments for the low range
> for 64-bit processes as well, and have them allocate their hugepages
> at >1TB?

You mean, forbid hugepages below 1TB?  That would be a user-visible
ABI change.  There are linker scripts for generating executables whose
text and/or data can go in hugepages, and I believe they put the
text/data below 1TB.

Paul.