[PATCH 4/6] 8xx: Tag DAR with 0x00f0 to catch buggy instructions.

[Joakim Tjernlund]

Benjamin Herrenschmidt <benh at kernel.crashing.org> wrote on 07/10/2009 23:18:21:
>
> On Wed, 2009-10-07 at 22:46 +0200, Joakim Tjernlund wrote:
> > dcbz, dcbf, dcbi, dcbst and icbi do not set DAR when they
> > cause a DTLB Error. Dectect this by tagging DAR with 0x00f0
> > at every exception exit that modifies DAR.
> > Test for DAR=0x00f0 in DataTLBError and bail
> > to handle_page_fault().
>
> Why not -1 ? :-)

Because 0x00f0 is already in use in the TLB fast path, saves one insn.