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

On 11/08/2026 1:11 pm, David Hildenbrand (Arm) wrote:

On 8/10/26 13:06, Muhammad Usama Anjum wrote:

quoted

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

quoted

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

quoted

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

quoted

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

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)
 {

I mean, how many such users do we expect? 1? :)

Why have a helper for that then, that seems to encourage it's use, when really
people should be using ptep_get() ?

There is only 1 direct dereference case and even that is for non-MMU case.
That's really good point. I'll keep using __pte_from_hw() and put a comment
in huge_ptep_clear_flush() that use of this must be avoided at all cost. An
API can be introduced in case more users arrive.

-- 
Thanks,
Usama