Re: [RFC PATCH 2/2] powerpc/mm/hash64: Map all the kernel mapping in the same 0xc range

Nicholas Piggin [off-list ref] writes:

Aneesh Kumar K.V's on February 19, 2019 4:00 pm:

quoted

On 2/19/19 11:28 AM, Nicholas Piggin wrote:

quoted

Aneesh Kumar K.V's on February 17, 2019 3:16 pm:

quoted

This patch maps vmap, IO and vmemap regions in the 0xc address range
instead of the current 0xd and 0xf range. This brings the mapping closer
to radix translation mode.

What was the reason for that address layout in the first place?

To bring in closer to radix translation mode and it should also help 
with KASAN implementation.

No I mean the old implementation. Your change seems fine, it would just
be good to know what the downside (if any) is from changing. Maybe it 
was just to make debugging slightly simpler?

I don't know what the reason was for using 0xd to begin with. The
original ppc64 port already had it.

Takes a few seconds to load:
  https://github.com/mpe/linux-fullhistory/commit/c3aa9878533e724f639852c3d951e6a169e04081#diff-0adfdefb64f0f0ef306be06ce7f953ebR173

#define PAGE_OFFSET     0xC000000000000000
#define KERNELBASE      PAGE_OFFSET
#define VMALLOCBASE     0xD000000000000000
#define IOREGIONBASE    0xE000000000000000


cheers