Re: [PATCH v2 3/9] powerpc/powernv: Remove real mode access limit for early allocations

On Mon, 2017-08-14 at 22:49 +1000, Michael Ellerman wrote:

quoted

-     /*
-      * We limit the allocation that depend on ppc64_rma_size
-      * to first_memblock_size. We also clamp it to 1GB to
-      * avoid some funky things such as RTAS bugs.

That comment about RTAS is 7 years old, and I'm pretty sure it was a
historical note when it was written.

I'm inclined to drop it and if we discover new bugs with RTAS on Power9
then we can always put it back.

Arent' we using a 32-bit RTAS ? (Afaik there's a 64-bit one, we just
never used it ..). In this case we need to at least clamp to 2G (no
trust RTAS doing unsigned properly).

quoted

-      *
-      * On radix config we really don't have a limitation
-      * on real mode access. But keeping it as above works
-      * well enough.

Ergh.

quoted

-      */
-     ppc64_rma_size = min_t(u64, first_memblock_size, 0x40000000);
-     /*
-      * Finally limit subsequent allocations. We really don't want
-      * to limit the memblock allocations to rma_size. FIXME!! should
-      * we even limit at all ?
-      */

So I think we should just delete this function entirely.

Any objections?

Well.. RTAS is quite sucky ... 

Ben.

cheers