Re: [PATCH v9 4/7] powerpc: mm: Default p{m,u}d_pte implementations

On 11/30/23 18:35, Christophe Leroy wrote:

Le 30/11/2023 à 03:53, Rohan McLure a écrit :

quoted

For 32-bit systems which have no usecases for p{m,u}d_pte() prior to
page table checking, implement default stubs.

Is that the best solution ?

If I understand correctly, it is only needed for 
pmd_user_accessible_page(). Why not provide a stub 
pmd_user_accessible_page() that returns false on those architectures ?

Yep, this seems reasonable to me.

Same for pud_user_accessible_page()

But if you decide to keep it I think that:
- It should be squashed with following patch to make it clear it's 
needed for that only.
- Remove the WARN_ONCE().

I might however move those WARN_ONCE() calls to the default, false-returning
p{m,u}d_user_accessible_page() implementations, to be consistent with
pud_pfn().

- Only have a special one for books/64 and a generic only common to he 3 
others.

quoted

Signed-off-by: Rohan McLure <redacted>
---
v9: New patch
---
  arch/powerpc/include/asm/book3s/64/pgtable.h |  3 +++
  arch/powerpc/include/asm/nohash/64/pgtable.h |  2 ++
  arch/powerpc/include/asm/pgtable.h           | 17 +++++++++++++++++
  3 files changed, 22 insertions(+)

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 8fdb7667c509..2454174b26cb 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h

@@ -887,6 +887,8 @@ static inline int pud_present(pud_t pud)
  
  extern struct page *pud_page(pud_t pud);
  extern struct page *pmd_page(pmd_t pmd);
+
+#define pud_pte pud_pte
  static inline pte_t pud_pte(pud_t pud)
  {
  	return __pte_raw(pud_raw(pud));

@@ -1043,6 +1045,7 @@ static inline void __kernel_map_pages(struct page *page, int numpages, int enabl
  }
  #endif
  
+#define pmd_pte pmd_pte
  static inline pte_t pmd_pte(pmd_t pmd)
  {
  	return __pte_raw(pmd_raw(pmd));

diff --git a/arch/powerpc/include/asm/nohash/64/pgtable.h b/arch/powerpc/include/asm/nohash/64/pgtable.h
index f58cbebde26e..09a34fe196ae 100644
--- a/arch/powerpc/include/asm/nohash/64/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/64/pgtable.h

@@ -93,6 +93,7 @@ static inline void pmd_clear(pmd_t *pmdp)
  	*pmdp = __pmd(0);
  }
  
+#define pmd_pte pmd_pte
  static inline pte_t pmd_pte(pmd_t pmd)
  {
  	return __pte(pmd_val(pmd));

@@ -134,6 +135,7 @@ static inline pmd_t *pud_pgtable(pud_t pud)
  
  extern struct page *pud_page(pud_t pud);
  
+#define pud_pte pud_pte
  static inline pte_t pud_pte(pud_t pud)
  {
  	return __pte(pud_val(pud));

diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index 9c0f2151f08f..d7d0f47760d3 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h

@@ -233,6 +233,23 @@ static inline int pud_pfn(pud_t pud)
  }
  #endif
  
+#ifndef pmd_pte
+#define pmd_pte pmd_pte
+static inline pte_t pmd_pte(pmd_t pmd)
+{
+	WARN_ONCE(1, "pmd: platform does not use pmd entries directly");
+	return __pte(pmd_val(pmd));
+}
+#endif
+
+#ifndef pud_pte
+#define pud_pte pud_pte
+static inline pte_t pud_pte(pud_t pud)
+{
+	WARN_ONCE(1, "pud: platform does not use pud entries directly");
+	return __pte(pud_val(pud));
+}
+#endif
  #endif /* __ASSEMBLY__ */
  
  #endif /* _ASM_POWERPC_PGTABLE_H */