Re: [PATCH 1/2] powerpc/64s: Rename PPC_INVALIDATE_ERAT to PPC_ARCH_300_INVALIDATE_ERAT

Nicholas Piggin [off-list ref] writes:

Segher Boessenkool's on June 23, 2019 10:03 pm:

quoted

On Sun, Jun 23, 2019 at 08:41:51PM +1000, Nicholas Piggin wrote:

quoted

This makes it clear to the caller that it can only be used on POWER9
and later CPUs.

quoted

-#define PPC_INVALIDATE_ERAT	PPC_SLBIA(7)
+#define PPC_ARCH_300_INVALIDATE_ERAT	PPC_SLBIA(7)

The architecture version is 3.0 (or 3.0B), not "300".  This will work on
implementations of later architecture versions as well, so maybe the name
isn't so great anyway?

Yeah... this is kernel convention for better or worse. ISA v3.0B
feature support is called CPU_FTR_ARCH_300, and later architectures
will advertise that support. For the most part we can use architected
features (incompatible changes would require additional code).

I'd rather we used 3_0B or something inside the kernel, but I'm not sure
it's worth the churn to rename the existing feature everywhere. And we
can't rename the user visible feature.

But if you're adding a new usage then I'd prefer: PPC_ISA_3_0B_INVALIDATE_ERAT

I dislike "300" because it implies we support ISA v3.0 but we actually
don't, we only support v3.0B.

cheers