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x86/hugetlb: use set_pmd for huge pte operations

PATCH In review Jeremy Fitzhardinge 1 participant 2 messages Jul 26, 2010 – Aug 4, 2010 x86

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Jeremy Fitzhardinge

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#0 lore raw

PATCH 1/1 x86/hugetlb: use set_pmd for huge pte operations

On x86, a huge pte is logically a pte, but structurally a pmd. Among other issues, pmds and ptes overload some flags for multiple uses (PAT vs PSE), so it is necessary to know which structural level a pagetable entry is in order interpret it properly.

When huge pages are used within a paravirtualized system, it is therefore appropriate to use the pmd set of function to operate on them, so that the hypervisor can correctly validate the update.

[ Add fix for 32-bit non-PAE with two-level pagetable - Jeremy ]

Signed-off-by Dave McCracken<[email protected]>
Signed-off-by Jeremy Fitzhardinge<[email protected]>
arch/x86/include/asm/hugetlb.h +26 -8
index 439a9ac..bf88684 100644
@@ -36,16 +36,28 @@ static inline void hugetlb_free_pgd_range(struct mmu_gather *tlb,
 	free_pgd_range(tlb, addr, end, floor, ceiling);
 }
 
+static inline pte_t huge_ptep_get(pte_t *ptep)
+{
+	return *ptep;
+}
+
 static inline void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
 				   pte_t *ptep, pte_t pte)
 {
-	set_pte_at(mm, addr, ptep, pte);
+#if PAGETABLE_LEVELS>= 3
+	set_pmd((pmd_t *)ptep, native_make_pmd(native_pte_val(pte)));
+#else
+	set_pgd((pgd_t *)ptep, native_make_pgd(native_pte_val(pte)));
+#endif
 }
 
 static inline pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
 					    unsigned long addr, pte_t *ptep)
 {
-	return ptep_get_and_clear(mm, addr, ptep);
+	pte_t pte = huge_ptep_get(ptep);
+
+	set_huge_pte_at(mm, addr, ptep, __pte(0));
+	return pte;
 }
 
 static inline void huge_ptep_clear_flush(struct vm_area_struct *vma,

@@ -66,19 +78,25 @@ static inline pte_t huge_pte_wrprotect(pte_t pte)
 static inline void huge_ptep_set_wrprotect(struct mm_struct *mm,
 					   unsigned long addr, pte_t *ptep)
 {
-	ptep_set_wrprotect(mm, addr, ptep);
+	pte_t pte = huge_ptep_get(ptep);
+
+	pte = pte_wrprotect(pte);
+	set_huge_pte_at(mm, addr, ptep, pte);
 }
 
 static inline int huge_ptep_set_access_flags(struct vm_area_struct *vma,
 					     unsigned long addr, pte_t *ptep,
 					     pte_t pte, int dirty)
 {
-	return ptep_set_access_flags(vma, addr, ptep, pte, dirty);
-}
+	pte_t oldpte = huge_ptep_get(ptep);
+	int changed = !pte_same(oldpte, pte);
 
-static inline pte_t huge_ptep_get(pte_t *ptep)
-{
-	return *ptep;
+	if (changed&&  dirty) {
+		set_huge_pte_at(vma->vm_mm, addr, ptep, pte);
+		flush_tlb_page(vma, addr);
+	}
+
+	return changed;
 }
 
 static inline int arch_prepare_hugepage(struct page *page)
author
#1 lore raw

On 07/26/2010 12:45 PM, Jeremy Fitzhardinge wrote:

Ping? I was about to send this to Linus, but I realized that I hadn't got any x86 acks on it. Any comments/complaints?

Thanks,
J

Quoted 92 lines

On x86, a huge pte is logically a pte, but structurally a pmd. Among other issues, pmds and ptes overload some flags for multiple uses (PAT vs PSE), so it is necessary to know which structural level a pagetable entry is in order interpret it properly.

When huge pages are used within a paravirtualized system, it is therefore appropriate to use the pmd set of function to operate on them, so that the hypervisor can correctly validate the update.

[ Add fix for 32-bit non-PAE with two-level pagetable - Jeremy ]

Signed-off-by Dave McCracken<[email protected]>
Signed-off-by Jeremy Fitzhardinge<[email protected]>
arch/x86/include/asm/hugetlb.h +14 -2
index 439a9ac..bf88684 100644
@@ -36,16 +36,28 @@ static inline void hugetlb_free_pgd_range(struct 
 mmu_gather *tlb,
     free_pgd_range(tlb, addr, end, floor, ceiling);
 }
 
+static inline pte_t huge_ptep_get(pte_t *ptep)
+{
+    return *ptep;
+}
+
 static inline void set_huge_pte_at(struct mm_struct *mm, unsigned 
 long addr,
                    pte_t *ptep, pte_t pte)
 {
-    set_pte_at(mm, addr, ptep, pte);
+#if PAGETABLE_LEVELS>= 3
+    set_pmd((pmd_t *)ptep, native_make_pmd(native_pte_val(pte)));
+#else
+    set_pgd((pgd_t *)ptep, native_make_pgd(native_pte_val(pte)));
+#endif
 }
 
 static inline pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
                         unsigned long addr, pte_t *ptep)
 {
-    return ptep_get_and_clear(mm, addr, ptep);
+    pte_t pte = huge_ptep_get(ptep);
+
+    set_huge_pte_at(mm, addr, ptep, __pte(0));
+    return pte;
 }

static inline void huge_ptep_clear_flush(struct vm_area_struct *vma,

arch/x86/include/asm/hugetlb.h +12 -6
@@ -66,19 +78,25 @@ static inline pte_t huge_pte_wrprotect(pte_t pte)
 static inline void huge_ptep_set_wrprotect(struct mm_struct *mm,
                        unsigned long addr, pte_t *ptep)
 {
-    ptep_set_wrprotect(mm, addr, ptep);
+    pte_t pte = huge_ptep_get(ptep);
+
+    pte = pte_wrprotect(pte);
+    set_huge_pte_at(mm, addr, ptep, pte);
 }
 
 static inline int huge_ptep_set_access_flags(struct vm_area_struct *vma,
                          unsigned long addr, pte_t *ptep,
                          pte_t pte, int dirty)
 {
-    return ptep_set_access_flags(vma, addr, ptep, pte, dirty);
-}
+    pte_t oldpte = huge_ptep_get(ptep);
+    int changed = !pte_same(oldpte, pte);
 
-static inline pte_t huge_ptep_get(pte_t *ptep)
-{
-    return *ptep;
+    if (changed&&  dirty) {
+        set_huge_pte_at(vma->vm_mm, addr, ptep, pte);
+        flush_tlb_page(vma, addr);
+    }
+
+    return changed;
 }
 
 static inline int arch_prepare_hugepage(struct page *page)
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