quoted

This isn't the way to do this.  We normally add entries in 
cputable.c an add a new cpu_feature_bit for the errata.

Than above we'd do:

if (cur_cpu_spec->cpu_features & CPU_FTR_E500_A005_ERRATUM)

IMHO, a cpu erratum is not a cpu feature.
See there're only 32 bits can be used for all PowerPC platform to represent cpu feature, 
then is it worth consuming one of them to represent one e500 erratum?

This is an interesting debate :-)

We have used cpu_features for errata in the past. However, we are
getting a bit short and I'd rather keep CPU features for things
that are spread out in multiple places and/or hitting hot code path.

If the workaround is very limited to a single non-critical code path,
testing the PVR might actually be a nicer way to do it.

Now, this specific patch is ... hrm ... hard to decide. I don't like
that much the global variable. On the other hand, it's static and allows
the whole business of this errata to be completely local to the
math_efp.c file which is a good thing.

So I'm tempted to say go with the patch as it-is, but I'll let Kumar
ultimately decide.

Cheers,
Ben.