The patch titled
Subject: ARC: mm: remove __ARCH_USE_5LEVEL_HACK
has been added to the -mm tree. Its filename is
arc-mm-remove-__arch_use_5level_hack.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/arc-mm-remove-__arch_use_5level_hack.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/arc-mm-remove-__arch_use_5level_hack.patch
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------------------------------------------------------
From: Vineet Gupta <Vineet.Gupta1@xxxxxxxxxxxx>
Subject: ARC: mm: remove __ARCH_USE_5LEVEL_HACK
Patch series "elide extraneous generated code for folded p4d/pud/pmd", v3.
This series came out of seemingly benign excursion into
understanding/removing __ARCH_USE_5LEVEL_HACK from ARC port showing some
extraneous code being generated despite folded p4d/pud/pmd
| bloat-o-meter2 vmlinux-[AB]*
| add/remove: 0/0 grow/shrink: 3/0 up/down: 130/0 (130)
| function old new delta
| free_pgd_range 548 660 +112
| p4d_clear_bad 2 20 +18
The patches here address that
| bloat-o-meter2 vmlinux-[BF]*
| add/remove: 0/2 grow/shrink: 0/1 up/down: 0/-386 (-386)
| function old new delta
| pud_clear_bad 20 - -20
| p4d_clear_bad 20 - -20
| free_pgd_range 660 314 -346
The code savings are not a whole lot, but still worthwhile IMHO.
This patch (of 5):
With paging code made 5-level compliant, this is no longer needed. ARC
has software page walker with 2 lookup levels (pgd -> pte)
This was expected to be non functional change but ended with slight
code bloat due to needless inclusions of p*d_free_tlb() macros which
will be addressed in further patches.
| bloat-o-meter2 vmlinux-[AB]*
| add/remove: 0/0 grow/shrink: 2/0 up/down: 128/0 (128)
| function old new delta
| free_pgd_range 546 656 +110
| p4d_clear_bad 2 20 +18
| Total: Before=4137148, After=4137276, chg 0.000000%
Link: http://lkml.kernel.org/r/20191016162400.14796-2-vgupta@xxxxxxxxxxxx
Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Nick Piggin <npiggin@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/arc/include/asm/pgtable.h | 1 -
arch/arc/mm/fault.c | 10 ++++++++--
arch/arc/mm/highmem.c | 4 +++-
3 files changed, 11 insertions(+), 4 deletions(-)
--- a/arch/arc/include/asm/pgtable.h~arc-mm-remove-__arch_use_5level_hack
+++ a/arch/arc/include/asm/pgtable.h
@@ -33,7 +33,6 @@
#define _ASM_ARC_PGTABLE_H
#include <linux/bits.h>
-#define __ARCH_USE_5LEVEL_HACK
#include <asm-generic/pgtable-nopmd.h>
#include <asm/page.h>
#include <asm/mmu.h> /* to propagate CONFIG_ARC_MMU_VER <n> */
--- a/arch/arc/mm/fault.c~arc-mm-remove-__arch_use_5level_hack
+++ a/arch/arc/mm/fault.c
@@ -30,6 +30,7 @@ noinline static int handle_kernel_vaddr_
* with the 'reference' page table.
*/
pgd_t *pgd, *pgd_k;
+ p4d_t *p4d, *p4d_k;
pud_t *pud, *pud_k;
pmd_t *pmd, *pmd_k;
@@ -39,8 +40,13 @@ noinline static int handle_kernel_vaddr_
if (!pgd_present(*pgd_k))
goto bad_area;
- pud = pud_offset(pgd, address);
- pud_k = pud_offset(pgd_k, address);
+ p4d = p4d_offset(pgd, address);
+ p4d_k = p4d_offset(pgd_k, address);
+ if (!p4d_present(*p4d_k))
+ goto bad_area;
+
+ pud = pud_offset(p4d, address);
+ pud_k = pud_offset(p4d_k, address);
if (!pud_present(*pud_k))
goto bad_area;
--- a/arch/arc/mm/highmem.c~arc-mm-remove-__arch_use_5level_hack
+++ a/arch/arc/mm/highmem.c
@@ -111,12 +111,14 @@ EXPORT_SYMBOL(__kunmap_atomic);
static noinline pte_t * __init alloc_kmap_pgtable(unsigned long kvaddr)
{
pgd_t *pgd_k;
+ p4d_t *p4d_k;
pud_t *pud_k;
pmd_t *pmd_k;
pte_t *pte_k;
pgd_k = pgd_offset_k(kvaddr);
- pud_k = pud_offset(pgd_k, kvaddr);
+ p4d_k = p4d_offset(pgd_k, kvaddr);
+ pud_k = pud_offset(p4d_k, kvaddr);
pmd_k = pmd_offset(pud_k, kvaddr);
pte_k = (pte_t *)memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
_
Patches currently in -mm which might be from Vineet.Gupta1@xxxxxxxxxxxx are
arc-mm-remove-__arch_use_5level_hack.patch
asm-generic-tlb-stub-out-pud_free_tlb-if-nopud.patch
asm-generic-tlb-stub-out-p4d_free_tlb-if-nop4d.patch
asm-generic-tlb-stub-out-pmd_free_tlb-if-nopmd.patch
asm-generic-mm-stub-out-p4ud_clear_bad-if-__pagetable_p4ud_folded.patch
