Re: [PATCH v7 10/14] mips: move has_transparent_hugepage() out of THP guard
From: Luiz Capitulino
Date: Wed Sep 02 2026 - 11:32:23 EST
On 2026-09-01 18:25, Thomas Bogendoerfer wrote:
On Tue, Sep 01, 2026 at 03:53:18PM -0400, Luiz Capitulino wrote:
On 2026-09-01 07:42, Lance Yang wrote:
On 2026/9/1 11:12, Luiz Capitulino wrote:
A future commit will introduce a kernel API to allow for checking if the
CPU supports PMD-sized pages. This API will be based on the
has_transparent_hugepage() implementation but will be orthogonal to THP
and therefore must work when CONFIG_TRANSPARENT_HUGEPAGE=n.
Move its definition out of the THP guard.
Signed-off-by: Luiz Capitulino <luizcap@xxxxxxxxxx>
---
arch/mips/include/asm/pgtable.h | 6 +++---
arch/mips/mm/tlb-r4k.c | 4 ----
2 files changed, 3 insertions(+), 7 deletions(-)
diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
index fa7b935f947c..b038da872ec6 100644
--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -615,9 +615,6 @@ unsigned long io_remap_pfn_range_pfn(unsigned long pfn, unsigned long size);
/* We don't have hardware dirty/accessed bits, generic_pmdp_establish is fine.*/
#define pmdp_establish generic_pmdp_establish
-#define has_transparent_hugepage has_transparent_hugepage
-extern int has_transparent_hugepage(void);
Assume a decstation_defconfig build. CPU_R3000 selects CPU_R3K_TLB, so the
Makefile builds tlb-r3k.o but not tlb-r4k.o IIUC ...
The only MIPS definition is in tlb-r4k.c, so R3000 would fail to link with
an undefined reference ... no?
Yes, you're right. I can reproduce this. Would the solution below be
acceptable?
diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
index fa7b935f947c..b038da872ec6 100644
--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -615,9 +615,6 @@ unsigned long io_remap_pfn_range_pfn(unsigned long pfn, unsigned long size);
/* We don't have hardware dirty/accessed bits, generic_pmdp_establish is fine.*/
#define pmdp_establish generic_pmdp_establish
-#define has_transparent_hugepage has_transparent_hugepage
-extern int has_transparent_hugepage(void);
-
static inline int pmd_trans_huge(pmd_t pmd)
{
return !!(pmd_val(pmd) & _PAGE_HUGE);
@@ -743,6 +740,9 @@ static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+#define has_transparent_hugepage has_transparent_hugepage
+extern int has_transparent_hugepage(void);
+
#ifdef _PAGE_HUGE
#define pmd_leaf(pmd) ((pmd_val(pmd) & _PAGE_HUGE) != 0)
#define pud_leaf(pud) ((pud_val(pud) & _PAGE_HUGE) != 0)
diff --git a/arch/mips/mm/pgtable.c b/arch/mips/mm/pgtable.c
index 10835414819f..3a5b411493d9 100644
--- a/arch/mips/mm/pgtable.c
+++ b/arch/mips/mm/pgtable.c
@@ -23,3 +23,30 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
return ret;
}
EXPORT_SYMBOL_GPL(pgd_alloc);
+
+#if defined(CONFIG_CPU_R4K_CACHE_TLB) || \
+ defined(CONFIG_CPU_SB1) || \
+ defined(CONFIG_CPU_CAVIUM_OCTEON)
I guess using CONFIG_CPU_SUPPORTS_HUGEPAGES is a better approach
Makes sense. Updated patch below.
Subject: [PATCH 10/14] mips: move has_transparent_hugepage() out of THP guard
A future commit will introduce a kernel API to allow for checking if the
CPU supports PMD-sized pages. This API will be based on the
has_transparent_hugepage() implementation but will be orthogonal to THP
and therefore must work when CONFIG_TRANSPARENT_HUGEPAGE=n.
This commit moves has_transparent_hugepage() definition to
arch/mips/mm/pgtable.c under CONFIG_CPU_SUPPORTS_HUGEPAGES guard in
order to ensure that it's only used in CPUs that support the register
operations performed.
Signed-off-by: Luiz Capitulino <luizcap@xxxxxxxxxx>
---
arch/mips/include/asm/pgtable.h | 6 +++---
arch/mips/mm/pgtable.c | 25 +++++++++++++++++++++++++
arch/mips/mm/tlb-r4k.c | 22 ----------------------
3 files changed, 28 insertions(+), 25 deletions(-)
diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
index fa7b935f947c..b038da872ec6 100644
--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -615,9 +615,6 @@ unsigned long io_remap_pfn_range_pfn(unsigned long pfn, unsigned long size);
/* We don't have hardware dirty/accessed bits, generic_pmdp_establish is fine.*/
#define pmdp_establish generic_pmdp_establish
-#define has_transparent_hugepage has_transparent_hugepage
-extern int has_transparent_hugepage(void);
-
static inline int pmd_trans_huge(pmd_t pmd)
{
return !!(pmd_val(pmd) & _PAGE_HUGE);
@@ -743,6 +740,9 @@ static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+#define has_transparent_hugepage has_transparent_hugepage
+extern int has_transparent_hugepage(void);
+
#ifdef _PAGE_HUGE
#define pmd_leaf(pmd) ((pmd_val(pmd) & _PAGE_HUGE) != 0)
#define pud_leaf(pud) ((pud_val(pud) & _PAGE_HUGE) != 0)
diff --git a/arch/mips/mm/pgtable.c b/arch/mips/mm/pgtable.c
index 10835414819f..4515fa42f0b3 100644
--- a/arch/mips/mm/pgtable.c
+++ b/arch/mips/mm/pgtable.c
@@ -23,3 +23,28 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
return ret;
}
EXPORT_SYMBOL_GPL(pgd_alloc);
+
+#ifdef CONFIG_CPU_SUPPORTS_HUGEPAGES
+int has_transparent_hugepage(void)
+{
+ static unsigned int mask = -1;
+
+ if (mask == -1) { /* first call comes during __init */
+ unsigned long flags;
+
+ local_irq_save(flags);
+ write_c0_pagemask(PM_HUGE_MASK);
+ back_to_back_c0_hazard();
+ mask = read_c0_pagemask();
+ write_c0_pagemask(PM_DEFAULT_MASK);
+ local_irq_restore(flags);
+ }
+ return mask == PM_HUGE_MASK;
+}
+#else
+int has_transparent_hugepage(void)
+{
+ return 0;
+}
+#endif
+EXPORT_SYMBOL(has_transparent_hugepage);
diff --git a/arch/mips/mm/tlb-r4k.c b/arch/mips/mm/tlb-r4k.c
index 24fe85fa169d..625f1c0dd71e 100644
--- a/arch/mips/mm/tlb-r4k.c
+++ b/arch/mips/mm/tlb-r4k.c
@@ -432,28 +432,6 @@ void add_wired_entry(unsigned long entrylo0, unsigned long entrylo1,
#endif
}
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-
-int has_transparent_hugepage(void)
-{
- static unsigned int mask = -1;
-
- if (mask == -1) { /* first call comes during __init */
- unsigned long flags;
-
- local_irq_save(flags);
- write_c0_pagemask(PM_HUGE_MASK);
- back_to_back_c0_hazard();
- mask = read_c0_pagemask();
- write_c0_pagemask(PM_DEFAULT_MASK);
- local_irq_restore(flags);
- }
- return mask == PM_HUGE_MASK;
-}
-EXPORT_SYMBOL(has_transparent_hugepage);
-
-#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
-
/*
* Used for loading TLB entries before trap_init() has started, when we
* don't actually want to add a wired entry which remains throughout the
--
2.55.0