Re: [PATCH 6/9] mm: convert PTE table entry to pte

On 10/08/2026 7:44 am, Alexander Gordeev wrote:

On Fri, Aug 07, 2026 at 05:26:04PM +0100, Muhammad Usama Anjum wrote:

quoted

On 07/08/2026 7:58 am, Alexander Gordeev wrote:

quoted

On Thu, Aug 06, 2026 at 09:38:44AM +0100, Muhammad Usama Anjum wrote:

quoted

The non-MMU stub receives hw_pte_t but returns a logical pte_t
value. Convert the stored entry through __pte_from_hw() before
returning.

Signed-off-by: Muhammad Usama Anjum <redacted>
---
 include/linux/hugetlb.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index bc0b9c65aa1d0..9e8b391aa4bc9 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h

@@ -1283,7 +1283,7 @@ static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
 #ifdef CONFIG_MMU
 	return ptep_get(ptep);
 #else
-	return *ptep;
+	return __pte_from_hw(*ptep);

But this is a direct dereferencing, which breaks the whole point, isn't it?

Yes, this is particular line is for non MMU. In this case, CONIFG_ARCH_HAS_HW_PTE
would never be defined. Hence hw_pte_t is just pte_t and direct dereference is
allowed. I'd thought a lot about it; is better to leave direct dereference here
or use some helper. Then used __pte_from_hw() was already being used in generic
ptep_get().

But in case CONIFG_ARCH_HAS_HW_PTE=n __pte_from_hw() is still gets called.
That looks inconsistent to me. Why not just call ptep_deref() (see below)?

Agreed. Calling __pte_from_hw() directly exposes the representation
conversion at the call site. I will introduce ptep_deref() and use it
here.

quoted

There are only two users of __pte_from_hw() at this time. 

quoted

What about introducing something like pte_t ptep_get_sw(hw_pte_t *ptep)
to be used in exactly situations like this? With that the semantics of
hw_pte_t pointers becomes straightforward and closes the still ongoing
"storage vs lifetime" discussion:

hw_pte_t*     points to HW-formatted page table entries

ptep_get()    is used to obtain HW-linked/attached entries, and may wire
              extra code like [1] or [2]

ptep_get_sw() is used to obtain HW-unlinked/unattached entries and in
              most cases is just a direct dereference

ptep_get_sw() or ptep_get_deref() is better name here?

ptep_deref() would be it.

Do you agree to the suggested API requirements?

Yes. hw_pte_t * identifies storage containing hardware-formatted PTEs,
regardless of whether it is attached. ptep_get() is used for attached
entries and may provide additional architecture-specific handling.
ptep_deref() is used for unattached entries and performs only the raw
storage-to-value conversion.

For review, this patch would become:

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index bc0b9c65aa1d0..ce900d2652d91 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h

@@ -1283,7 +1283,7 @@ static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
 #ifdef CONFIG_MMU
 	return ptep_get(ptep);
 #else
-	return *ptep;
+	return ptep_deref(ptep);
 #endif
 }
 

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 1768421755a9c..08613593f3320 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h

@@ -490,6 +490,13 @@ static inline int pudp_set_access_flags(struct vm_area_struct *vma,
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif
 
+#ifndef ptep_deref
+static inline pte_t ptep_deref(hw_pte_t *ptep)
+{
+	return __pte_from_hw(*ptep);
+}
+#endif
+
 #ifndef ptep_get
 static inline pte_t ptep_get(hw_pte_t *ptep)
 {

-- 
Thanks,
Usama