Re: [PATCH] powerpc: add support for folded p4d page tables

Mike Rapoport
2020-01-06T06:02:27Z

On Mon, Jan 06, 2020 at 02:31:41PM +1100, Michael Ellerman wrote:
> Mike Rapoport <rppt@kernel.org> writes:
> > Any updates on this?
>
> It's very ... big, and kind of intrusive.

I've tried to split it to several smaller ones, but I couldn't find a way
to do it without breaking bisectability.

As for the intrusive, most of the changes are mechanical

> It's not an improvement as far as the powerpc code's readability is
> concerned. I assume the plan is that the 5-level hack can eventually be
> removed and so this conversion is a prerequisite for that?

Yep, the idea is to remove asm-generic/pgtable-nop4d-hack.h and
asm-generic/5level-fixup.h.

And, there is a small benefit for powerpc as kernel size is reduced a bit,
e.g. for pseries_defconfig:

$ size old/vmlinux new/vmlinux
text data bss dec hex filename
13702955 5961022 1517520 21181497 1433439 old/vmlinux
13702507 5961006 1517520 21181033 1433269 new/vmlinux

> cheers
>
> > On Mon, Dec 09, 2019 at 05:09:08PM +0200, Mike Rapoport wrote:
> >> From: Mike Rapoport <rppt@linux.ibm.com>
> >>
> >> Implement primitives necessary for the 4th level folding, add walks of p4d
> >> level where appropriate and replace 5level-fixup.h with pgtable-nop4d.h.
> >>
> >> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> >> ---
> >> arch/powerpc/include/asm/book3s/32/pgtable.h | 1 -
> >> arch/powerpc/include/asm/book3s/64/hash.h | 4 +-
> >> arch/powerpc/include/asm/book3s/64/pgalloc.h | 4 +-
> >> arch/powerpc/include/asm/book3s/64/pgtable.h | 58 ++++++++++--------
> >> arch/powerpc/include/asm/book3s/64/radix.h | 6 +-
> >> arch/powerpc/include/asm/nohash/32/pgtable.h | 1 -
> >> arch/powerpc/include/asm/nohash/64/pgalloc.h | 2 +-
> >> .../include/asm/nohash/64/pgtable-4k.h | 32 +++++-----
> >> arch/powerpc/include/asm/nohash/64/pgtable.h | 6 +-
> >> arch/powerpc/include/asm/pgtable.h | 8 +++
> >> arch/powerpc/kvm/book3s_64_mmu_radix.c | 59 ++++++++++++++++---
> >> arch/powerpc/lib/code-patching.c | 7 ++-
> >> arch/powerpc/mm/book3s32/mmu.c | 2 +-
> >> arch/powerpc/mm/book3s32/tlb.c | 4 +-
> >> arch/powerpc/mm/book3s64/hash_pgtable.c | 4 +-
> >> arch/powerpc/mm/book3s64/radix_pgtable.c | 19 ++++--
> >> arch/powerpc/mm/book3s64/subpage_prot.c | 6 +-
> >> arch/powerpc/mm/hugetlbpage.c | 28 +++++----
> >> arch/powerpc/mm/kasan/kasan_init_32.c | 8 +--
> >> arch/powerpc/mm/mem.c | 4 +-
> >> arch/powerpc/mm/nohash/40x.c | 4 +-
> >> arch/powerpc/mm/nohash/book3e_pgtable.c | 15 +++--
> >> arch/powerpc/mm/pgtable.c | 25 +++++++-
> >> arch/powerpc/mm/pgtable_32.c | 28 +++++----
> >> arch/powerpc/mm/pgtable_64.c | 10 ++--
> >> arch/powerpc/mm/ptdump/hashpagetable.c | 20 ++++++-
> >> arch/powerpc/mm/ptdump/ptdump.c | 22 ++++++-
> >> arch/powerpc/xmon/xmon.c | 17 +++++-
> >> 28 files changed, 284 insertions(+), 120 deletions(-)
>

--
Sincerely yours,
Mike.