[PATCH] arm64/mm: Add pud_sect_supported()

From: Anshuman Khandual
Date: Tue Sep 14 2021 - 23:43:30 EST


Section mapping at PUD level is supported only on 4K pages and currently it
gets verified with explicit #ifdef or IS_ENABLED() constructs. This adds a
new helper pud_sect_supported() for this purpose, which particularly cleans
up the HugeTLB code path. It updates relevant switch statements with checks
for __PAGETABLE_PUD_FOLDED in order to avoid build failures caused with two
identical switch case values in those code blocks.

Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Suggested-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
This applies on v5.15-rc1

arch/arm64/include/asm/pgtable.h | 5 +++++
arch/arm64/include/asm/vmalloc.h | 4 ++--
arch/arm64/mm/hugetlbpage.c | 26 +++++++++++++++-----------
3 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index dfa76afa0ccf..84fbb52b4224 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -1022,6 +1022,11 @@ static inline pgprot_t arch_filter_pgprot(pgprot_t prot)
return PAGE_READONLY_EXEC;
}

+static inline bool pud_sect_supported(void)
+{
+ return PAGE_SIZE == SZ_4K;
+}
+

#endif /* !__ASSEMBLY__ */

diff --git a/arch/arm64/include/asm/vmalloc.h b/arch/arm64/include/asm/vmalloc.h
index 7a22aeea9bb5..b9185503feae 100644
--- a/arch/arm64/include/asm/vmalloc.h
+++ b/arch/arm64/include/asm/vmalloc.h
@@ -2,6 +2,7 @@
#define _ASM_ARM64_VMALLOC_H

#include <asm/page.h>
+#include <asm/pgtable.h>

#ifdef CONFIG_HAVE_ARCH_HUGE_VMAP

@@ -9,10 +10,9 @@
static inline bool arch_vmap_pud_supported(pgprot_t prot)
{
/*
- * Only 4k granule supports level 1 block mappings.
* SW table walks can't handle removal of intermediate entries.
*/
- return IS_ENABLED(CONFIG_ARM64_4K_PAGES) &&
+ return pud_sect_supported() &&
!IS_ENABLED(CONFIG_PTDUMP_DEBUGFS);
}

diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 23505fc35324..641854f0e8ee 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -40,11 +40,10 @@ void __init arm64_hugetlb_cma_reserve(void)
{
int order;

-#ifdef CONFIG_ARM64_4K_PAGES
- order = PUD_SHIFT - PAGE_SHIFT;
-#else
- order = CONT_PMD_SHIFT + PMD_SHIFT - PAGE_SHIFT;
-#endif
+ if (pud_sect_supported())
+ order = PUD_SHIFT - PAGE_SHIFT;
+ else
+ order = CONT_PMD_SHIFT + PMD_SHIFT - PAGE_SHIFT;
/*
* HugeTLB CMA reservation is required for gigantic
* huge pages which could not be allocated via the
@@ -62,8 +61,9 @@ bool arch_hugetlb_migration_supported(struct hstate *h)
size_t pagesize = huge_page_size(h);

switch (pagesize) {
-#ifdef CONFIG_ARM64_4K_PAGES
+#ifndef __PAGETABLE_PUD_FOLDED
case PUD_SIZE:
+ return pud_sect_supported();
#endif
case PMD_SIZE:
case CONT_PMD_SIZE:
@@ -126,8 +126,11 @@ static inline int num_contig_ptes(unsigned long size, size_t *pgsize)
*pgsize = size;

switch (size) {
-#ifdef CONFIG_ARM64_4K_PAGES
+#ifndef __PAGETABLE_PUD_FOLDED
case PUD_SIZE:
+ if (pud_sect_supported())
+ contig_ptes = 1;
+ break;
#endif
case PMD_SIZE:
contig_ptes = 1;
@@ -489,9 +492,9 @@ void huge_ptep_clear_flush(struct vm_area_struct *vma,

static int __init hugetlbpage_init(void)
{
-#ifdef CONFIG_ARM64_4K_PAGES
- hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
-#endif
+ if (pud_sect_supported())
+ hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
+
hugetlb_add_hstate(CONT_PMD_SHIFT - PAGE_SHIFT);
hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
hugetlb_add_hstate(CONT_PTE_SHIFT - PAGE_SHIFT);
@@ -503,8 +506,9 @@ arch_initcall(hugetlbpage_init);
bool __init arch_hugetlb_valid_size(unsigned long size)
{
switch (size) {
-#ifdef CONFIG_ARM64_4K_PAGES
+#ifndef __PAGETABLE_PUD_FOLDED
case PUD_SIZE:
+ return pud_sect_supported();
#endif
case CONT_PMD_SIZE:
case PMD_SIZE:
--
2.20.1