[RFC] 16K page size for kernel thread stack (patch)

[Juli Mallett]

On Wed, Feb 19, 2014 at 11:41 AM, Stacey Son <sson at freebsd.org> wrote:
>
>  On Feb 18, 2014, at 7:58 PM, Adrian Chadd <adrian at freebsd.org> wrote:
> > I don't think the mips24k/mips74k cores I have support ULRI.
>
> I am starting to wonder which mips CPUs actually do have an ULRI.
>

Basically-none.  Some sources I've read from when the rdhwr approach was
first implemented clearly thought it would pretty much never be implemented
in hardware, and certainly most implementations after it became widespread
didn't implement it, and its use only became common in the recent past.
 Until we started using it for TLS, GXemul would exit rather than trap on
the rdhwr.  I don't believe I've ever possessed a piece of hardware which
actually implements the register itself, and there's actually a huge
disincentive to do so because a lot of software has been written now which
assumes that rdhwr will always trap and be implemented in software, and so
won't set up the actual hardware register with the right value, breaking
existing software.

Juli.