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@synopsys.com
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Nick Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h
index 7addd03..b917b59 100644 (file)
--- a/arch/arc/include/asm/pgtable.h
+++ b/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> */

diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c
index 3861543..fb86bc3 100644 (file)
--- a/arch/arc/mm/fault.c
+++ b/arch/arc/mm/fault.c
@@ -30,6 +30,7 @@ noinline static int handle_kernel_vaddr_fault(unsigned long address)
         * 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_fault(unsigned long address)
        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;
 

diff --git a/arch/arc/mm/highmem.c b/arch/arc/mm/highmem.c
index a4856bf..fc8849e 100644 (file)
--- a/arch/arc/mm/highmem.c
+++ b/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);