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); _
