Re: [PATCH v7 10/14] mips: move has_transparent_hugepage() out of THP guard

[Luiz Capitulino <luizcap@redhat.com>]

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@redhat.com>
>> ---
>>   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)
+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