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NestMMU pte upgrade workaround for mprotect

PATCH Superseded Aneesh Kumar K.V 2 participants 10 messages Nov 28, 2018 – Dec 4, 2018

Subsystems (11)
Memory management x86 PowerPC MM core +7 more subsystems

v2 of 5 Superseded Latest is v5 →

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Aneesh Kumar K.V

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#0 lore raw

v2 cover NestMMU pte upgrade workaround for mprotect

We can upgrade pte access (R -> RW transition) via mprotect. We need
to make sure we follow the recommended pte update sequence as outlined in
commit: bd5050e38aec ("powerpc/mm/radix: Change pte relax sequence to handle nest MMU hang") for such updates. This patch series do that.

Changes from V1:
* Restrict ths only for R->RW upgrade. We don't need to do this for Autonuma
* Restrict this only for radix translation mode.

Aneesh Kumar K.V (5):
mm: Update ptep_modify_prot_start/commit to take vm_area_struct as arg
mm: update ptep_modify_prot_commit to take old pte value as arg arch/powerpc/mm: Nest MMU workaround for mprotect RW upgrade. mm/hugetlb: Add prot_modify_start/commit sequence for hugetlb update arch/powerpc/mm/hugetlb: NestMMU workaround for hugetlb mprotect RW
upgrade

 arch/powerpc/include/asm/book3s/64/hugetlb.h | 12 ++++++++
 arch/powerpc/include/asm/book3s/64/pgtable.h | 18 ++++++++++++
 arch/powerpc/include/asm/book3s/64/radix.h   |  4 +++
 arch/powerpc/mm/hugetlbpage-radix.c          | 17 ++++++++++++
 arch/powerpc/mm/hugetlbpage.c                | 29 ++++++++++++++++++++
 arch/powerpc/mm/pgtable-book3s64.c           | 27 ++++++++++++++++++
 arch/powerpc/mm/pgtable-radix.c              | 18 ++++++++++++
 arch/s390/include/asm/pgtable.h              |  5 ++--
 arch/s390/mm/pgtable.c                       |  8 ++++--
 arch/x86/include/asm/paravirt.h              |  9 ++++--
 fs/proc/task_mmu.c                           |  8 ++++--
 include/asm-generic/pgtable.h                | 10 +++----
 include/linux/hugetlb.h                      | 18 ++++++++++++
 mm/hugetlb.c                                 |  8 ++++--
 mm/memory.c                                  |  8 +++---
 mm/mprotect.c                                |  6 ++--
 16 files changed, 179 insertions(+), 26 deletions(-)
Signature · 1 line
2.19.1
author
#1 lore raw

PATCH v2 1/5 mm: Update ptep_modify_prot_start/commit to take vm_area_struct as arg

Some architecture may want to call flush_tlb_range from these helpers.

Signed-off-by Aneesh Kumar K.V <[email protected]>
---
 arch/s390/include/asm/pgtable.h | 4 ++--
 arch/s390/mm/pgtable.c          | 6 ++++--
 arch/x86/include/asm/paravirt.h | 7 +++++--
 fs/proc/task_mmu.c              | 4 ++--
 include/asm-generic/pgtable.h   | 8 ++++----
 mm/memory.c                     | 4 ++--
 mm/mprotect.c                   | 4 ++--
 7 files changed, 21 insertions(+), 16 deletions(-)
arch/s390/include/asm/pgtable.h +2 -2
index 063732414dfb..5d730199e37b 100644
@@ -1069,8 +1069,8 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
 }
 
 #define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION
-pte_t ptep_modify_prot_start(struct mm_struct *, unsigned long, pte_t *);
-void ptep_modify_prot_commit(struct mm_struct *, unsigned long, pte_t *, pte_t);
+pte_t ptep_modify_prot_start(struct vm_area_struct *, unsigned long, pte_t *);
+void ptep_modify_prot_commit(struct vm_area_struct *, unsigned long, pte_t *, pte_t);
 
 #define __HAVE_ARCH_PTEP_CLEAR_FLUSH
 static inline pte_t ptep_clear_flush(struct vm_area_struct *vma,
arch/s390/mm/pgtable.c +4 -2
index f2cc7da473e4..29c0a21cd34a 100644
@@ -301,12 +301,13 @@ pte_t ptep_xchg_lazy(struct mm_struct *mm, unsigned long addr,
 }
 EXPORT_SYMBOL(ptep_xchg_lazy);
 
-pte_t ptep_modify_prot_start(struct mm_struct *mm, unsigned long addr,
+pte_t ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr,
 			     pte_t *ptep)
 {
 	pgste_t pgste;
 	pte_t old;
 	int nodat;
+	struct mm_struct *mm = vma->vm_mm;
 
 	preempt_disable();
 	pgste = ptep_xchg_start(mm, addr, ptep);

@@ -320,10 +321,11 @@ pte_t ptep_modify_prot_start(struct mm_struct *mm, unsigned long addr,
 }
 EXPORT_SYMBOL(ptep_modify_prot_start);
 
-void ptep_modify_prot_commit(struct mm_struct *mm, unsigned long addr,
+void ptep_modify_prot_commit(struct vm_area_struct *vma, unsigned long addr,
 			     pte_t *ptep, pte_t pte)
 {
 	pgste_t pgste;
+	struct mm_struct *mm = vma->vm_mm;
 
 	if (!MACHINE_HAS_NX)
 		pte_val(pte) &= ~_PAGE_NOEXEC;
arch/x86/include/asm/paravirt.h +5 -2
index 4bf42f9e4eea..1154f154025d 100644
@@ -417,19 +417,22 @@ static inline pgdval_t pgd_val(pgd_t pgd)
 }
 
 #define  __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION
-static inline pte_t ptep_modify_prot_start(struct mm_struct *mm, unsigned long addr,
+static inline pte_t ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr,
 					   pte_t *ptep)
 {
 	pteval_t ret;
+	struct mm_struct *mm = vma->vm_mm;
 
 	ret = PVOP_CALL3(pteval_t, mmu.ptep_modify_prot_start, mm, addr, ptep);
 
 	return (pte_t) { .pte = ret };
 }
 
-static inline void ptep_modify_prot_commit(struct mm_struct *mm, unsigned long addr,
+static inline void ptep_modify_prot_commit(struct vm_area_struct *vma, unsigned long addr,
 					   pte_t *ptep, pte_t pte)
 {
+	struct mm_struct *mm = vma->vm_mm;
+
 	if (sizeof(pteval_t) > sizeof(long))
 		/* 5 arg words */
 		pv_ops.mmu.ptep_modify_prot_commit(mm, addr, ptep, pte);
fs/proc/task_mmu.c +2 -2
index 47c3764c469b..9952d7185170 100644
@@ -940,10 +940,10 @@ static inline void clear_soft_dirty(struct vm_area_struct *vma,
 	pte_t ptent = *pte;
 
 	if (pte_present(ptent)) {
-		ptent = ptep_modify_prot_start(vma->vm_mm, addr, pte);
+		ptent = ptep_modify_prot_start(vma, addr, pte);
 		ptent = pte_wrprotect(ptent);
 		ptent = pte_clear_soft_dirty(ptent);
-		ptep_modify_prot_commit(vma->vm_mm, addr, pte, ptent);
+		ptep_modify_prot_commit(vma, addr, pte, ptent);
 	} else if (is_swap_pte(ptent)) {
 		ptent = pte_swp_clear_soft_dirty(ptent);
 		set_pte_at(vma->vm_mm, addr, pte, ptent);
include/asm-generic/pgtable.h +4 -4
index 359fb935ded6..c9897dcc46c4 100644
@@ -606,22 +606,22 @@ static inline void __ptep_modify_prot_commit(struct mm_struct *mm,
  * queue the update to be done at some later time.  The update must be
  * actually committed before the pte lock is released, however.
  */
-static inline pte_t ptep_modify_prot_start(struct mm_struct *mm,
+static inline pte_t ptep_modify_prot_start(struct vm_area_struct *vma,
 					   unsigned long addr,
 					   pte_t *ptep)
 {
-	return __ptep_modify_prot_start(mm, addr, ptep);
+	return __ptep_modify_prot_start(vma->vm_mm, addr, ptep);
 }
 
 /*
  * Commit an update to a pte, leaving any hardware-controlled bits in
  * the PTE unmodified.
  */
-static inline void ptep_modify_prot_commit(struct mm_struct *mm,
+static inline void ptep_modify_prot_commit(struct vm_area_struct *vma,
 					   unsigned long addr,
 					   pte_t *ptep, pte_t pte)
 {
-	__ptep_modify_prot_commit(mm, addr, ptep, pte);
+	__ptep_modify_prot_commit(vma->vm_mm, addr, ptep, pte);
 }
 #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */
 #endif /* CONFIG_MMU */
mm/memory.c +2 -2
index 4ad2d293ddc2..d36b0eaa7862 100644
@@ -3588,12 +3588,12 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
 	 * Make it present again, Depending on how arch implementes non
 	 * accessible ptes, some can allow access by kernel mode.
 	 */
-	pte = ptep_modify_prot_start(vma->vm_mm, vmf->address, vmf->pte);
+	pte = ptep_modify_prot_start(vma, vmf->address, vmf->pte);
 	pte = pte_modify(pte, vma->vm_page_prot);
 	pte = pte_mkyoung(pte);
 	if (was_writable)
 		pte = pte_mkwrite(pte);
-	ptep_modify_prot_commit(vma->vm_mm, vmf->address, vmf->pte, pte);
+	ptep_modify_prot_commit(vma, vmf->address, vmf->pte, pte);
 	update_mmu_cache(vma, vmf->address, vmf->pte);
 
 	page = vm_normal_page(vma, vmf->address, pte);
mm/mprotect.c +2 -2
index 6d331620b9e5..a301d4c83d3c 100644
@@ -110,7 +110,7 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 					continue;
 			}
 
-			ptent = ptep_modify_prot_start(mm, addr, pte);
+			ptent = ptep_modify_prot_start(vma, addr, pte);
 			ptent = pte_modify(ptent, newprot);
 			if (preserve_write)
 				ptent = pte_mk_savedwrite(ptent);

@@ -121,7 +121,7 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 					 !(vma->vm_flags & VM_SOFTDIRTY))) {
 				ptent = pte_mkwrite(ptent);
 			}
-			ptep_modify_prot_commit(mm, addr, pte, ptent);
+			ptep_modify_prot_commit(vma, addr, pte, ptent);
 			pages++;
 		} else if (IS_ENABLED(CONFIG_MIGRATION)) {
 			swp_entry_t entry = pte_to_swp_entry(oldpte);
Signature · 1 line
2.19.1
author
#2 lore raw

PATCH v2 2/5 mm: update ptep_modify_prot_commit to take old pte value as arg

In reply to Aneesh Kumar K.V

Architectures like ppc64 requires to do a conditional tlb flush based on the old and new value of pte. Enable that by passing old pte value as the arg.

Signed-off-by Aneesh Kumar K.V <[email protected]>
---
 arch/s390/include/asm/pgtable.h | 3 ++-
 arch/s390/mm/pgtable.c          | 2 +-
 arch/x86/include/asm/paravirt.h | 2 +-
 fs/proc/task_mmu.c              | 8 +++++---
 include/asm-generic/pgtable.h   | 2 +-
 mm/memory.c                     | 8 ++++----
 mm/mprotect.c                   | 6 +++---
 7 files changed, 17 insertions(+), 14 deletions(-)
arch/s390/include/asm/pgtable.h +2 -1
index 5d730199e37b..76dc344edb8c 100644
@@ -1070,7 +1070,8 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
 
 #define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION
 pte_t ptep_modify_prot_start(struct vm_area_struct *, unsigned long, pte_t *);
-void ptep_modify_prot_commit(struct vm_area_struct *, unsigned long, pte_t *, pte_t);
+void ptep_modify_prot_commit(struct vm_area_struct *, unsigned long,
+			     pte_t *, pte_t, pte_t);
 
 #define __HAVE_ARCH_PTEP_CLEAR_FLUSH
 static inline pte_t ptep_clear_flush(struct vm_area_struct *vma,
arch/s390/mm/pgtable.c +1 -1
index 29c0a21cd34a..b283b92722cc 100644
@@ -322,7 +322,7 @@ pte_t ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr,
 EXPORT_SYMBOL(ptep_modify_prot_start);
 
 void ptep_modify_prot_commit(struct vm_area_struct *vma, unsigned long addr,
-			     pte_t *ptep, pte_t pte)
+			     pte_t *ptep, pte_t old_pte, pte_t pte)
 {
 	pgste_t pgste;
 	struct mm_struct *mm = vma->vm_mm;
arch/x86/include/asm/paravirt.h +1 -1
index 1154f154025d..0d75a4f60500 100644
@@ -429,7 +429,7 @@ static inline pte_t ptep_modify_prot_start(struct vm_area_struct *vma, unsigned
 }
 
 static inline void ptep_modify_prot_commit(struct vm_area_struct *vma, unsigned long addr,
-					   pte_t *ptep, pte_t pte)
+					   pte_t *ptep, pte_t old_pte, pte_t pte)
 {
 	struct mm_struct *mm = vma->vm_mm;
fs/proc/task_mmu.c +5 -3
index 9952d7185170..8d62891d38a8 100644
@@ -940,10 +940,12 @@ static inline void clear_soft_dirty(struct vm_area_struct *vma,
 	pte_t ptent = *pte;
 
 	if (pte_present(ptent)) {
-		ptent = ptep_modify_prot_start(vma, addr, pte);
-		ptent = pte_wrprotect(ptent);
+		pte_t old_pte;
+
+		old_pte = ptep_modify_prot_start(vma, addr, pte);
+		ptent = pte_wrprotect(old_pte);
 		ptent = pte_clear_soft_dirty(ptent);
-		ptep_modify_prot_commit(vma, addr, pte, ptent);
+		ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent);
 	} else if (is_swap_pte(ptent)) {
 		ptent = pte_swp_clear_soft_dirty(ptent);
 		set_pte_at(vma->vm_mm, addr, pte, ptent);
include/asm-generic/pgtable.h +1 -1
index c9897dcc46c4..37039e918f17 100644
@@ -619,7 +619,7 @@ static inline pte_t ptep_modify_prot_start(struct vm_area_struct *vma,
  */
 static inline void ptep_modify_prot_commit(struct vm_area_struct *vma,
 					   unsigned long addr,
-					   pte_t *ptep, pte_t pte)
+					   pte_t *ptep, pte_t old_pte, pte_t pte)
 {
 	__ptep_modify_prot_commit(vma->vm_mm, addr, ptep, pte);
 }
mm/memory.c +4 -4
index d36b0eaa7862..4f3ddaedc764 100644
@@ -3568,7 +3568,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
 	int last_cpupid;
 	int target_nid;
 	bool migrated = false;
-	pte_t pte;
+	pte_t pte, old_pte;
 	bool was_writable = pte_savedwrite(vmf->orig_pte);
 	int flags = 0;
 

@@ -3588,12 +3588,12 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
 	 * Make it present again, Depending on how arch implementes non
 	 * accessible ptes, some can allow access by kernel mode.
 	 */
-	pte = ptep_modify_prot_start(vma, vmf->address, vmf->pte);
-	pte = pte_modify(pte, vma->vm_page_prot);
+	old_pte = ptep_modify_prot_start(vma, vmf->address, vmf->pte);
+	pte = pte_modify(old_pte, vma->vm_page_prot);
 	pte = pte_mkyoung(pte);
 	if (was_writable)
 		pte = pte_mkwrite(pte);
-	ptep_modify_prot_commit(vma, vmf->address, vmf->pte, pte);
+	ptep_modify_prot_commit(vma, vmf->address, vmf->pte, old_pte, pte);
 	update_mmu_cache(vma, vmf->address, vmf->pte);
 
 	page = vm_normal_page(vma, vmf->address, pte);
mm/mprotect.c +3 -3
index a301d4c83d3c..1b46b1b1248d 100644
@@ -110,8 +110,8 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 					continue;
 			}
 
-			ptent = ptep_modify_prot_start(vma, addr, pte);
-			ptent = pte_modify(ptent, newprot);
+			oldpte = ptep_modify_prot_start(vma, addr, pte);
+			ptent = pte_modify(oldpte, newprot);
 			if (preserve_write)
 				ptent = pte_mk_savedwrite(ptent);
 

@@ -121,7 +121,7 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 					 !(vma->vm_flags & VM_SOFTDIRTY))) {
 				ptent = pte_mkwrite(ptent);
 			}
-			ptep_modify_prot_commit(vma, addr, pte, ptent);
+			ptep_modify_prot_commit(vma, addr, pte, oldpte, ptent);
 			pages++;
 		} else if (IS_ENABLED(CONFIG_MIGRATION)) {
 			swp_entry_t entry = pte_to_swp_entry(oldpte);
Signature · 1 line
2.19.1
author
#3 lore raw

PATCH v2 3/5 arch/powerpc/mm: Nest MMU workaround for mprotect RW upgrade.

In reply to Aneesh Kumar K.V

NestMMU requires us to mark the pte invalid and flush the tlb when we do a RW upgrade of pte. We fixed a variant of this in the fault path in commit

Fixes bd5050e38aec ("powerpc/mm/radix: Change pte relax sequence to handle nest MMU hang")

Do the same for mprotect upgrades.

Hugetlb is handled in the next patch.

Signed-off-by Aneesh Kumar K.V <[email protected]>
---
 arch/powerpc/include/asm/book3s/64/pgtable.h | 18 +++++++++++++
 arch/powerpc/include/asm/book3s/64/radix.h   |  4 +++
 arch/powerpc/mm/pgtable-book3s64.c           | 27 ++++++++++++++++++++
 arch/powerpc/mm/pgtable-radix.c              | 18 +++++++++++++
 4 files changed, 67 insertions(+)
arch/powerpc/include/asm/book3s/64/pgtable.h +18 -0
index 2e6ada28da64..92eaea164700 100644
@@ -1314,6 +1314,24 @@ static inline int pud_pfn(pud_t pud)
 	BUILD_BUG();
 	return 0;
 }
+#define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION
+pte_t ptep_modify_prot_start(struct vm_area_struct *, unsigned long, pte_t *);
+void ptep_modify_prot_commit(struct vm_area_struct *, unsigned long,
+			     pte_t *, pte_t, pte_t);
+
+/*
+ * Returns true for a R -> RW upgrade of pte
+ */
+static inline bool is_pte_rw_upgrade(unsigned long old_val, unsigned long new_val)
+{
+	if (!(old_val & _PAGE_READ))
+		return false;
+
+	if ((!(old_val & _PAGE_WRITE)) && (new_val & _PAGE_WRITE))
+		return true;
+
+	return false;
+}
 
 #endif /* __ASSEMBLY__ */
 #endif /* _ASM_POWERPC_BOOK3S_64_PGTABLE_H_ */
arch/powerpc/include/asm/book3s/64/radix.h +4 -0
index 7d1a3d1543fc..5ab134eeed20 100644
@@ -127,6 +127,10 @@ extern void radix__ptep_set_access_flags(struct vm_area_struct *vma, pte_t *ptep
 					 pte_t entry, unsigned long address,
 					 int psize);
 
+extern void radix__ptep_modify_prot_commit(struct vm_area_struct *vma,
+					   unsigned long addr, pte_t *ptep,
+					   pte_t old_pte, pte_t pte);
+
 static inline unsigned long __radix_pte_update(pte_t *ptep, unsigned long clr,
 					       unsigned long set)
 {
arch/powerpc/mm/pgtable-book3s64.c +27 -0
index 9f93c9f985c5..3d126353b11e 100644
@@ -482,3 +482,30 @@ void arch_report_meminfo(struct seq_file *m)
 		   atomic_long_read(&direct_pages_count[MMU_PAGE_1G]) << 20);
 }
 #endif /* CONFIG_PROC_FS */
+
+pte_t ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr,
+			     pte_t *ptep)
+{
+	unsigned long pte_val;
+
+	/*
+	 * Clear the _PAGE_PRESENT so that no hardware parallel update is
+	 * possible. Also keep the pte_present true so that we don't take
+	 * wrong fault.
+	 */
+	pte_val = pte_update(vma->vm_mm, addr, ptep, _PAGE_PRESENT, _PAGE_INVALID, 0);
+
+	return __pte(pte_val);
+
+}
+EXPORT_SYMBOL(ptep_modify_prot_start);
+
+void ptep_modify_prot_commit(struct vm_area_struct *vma, unsigned long addr,
+			     pte_t *ptep, pte_t old_pte, pte_t pte)
+{
+	if (radix_enabled())
+		return radix__ptep_modify_prot_commit(vma, addr,
+						      ptep, old_pte, pte);
+	set_pte_at(vma->vm_mm, addr, ptep, pte);
+}
+EXPORT_SYMBOL(ptep_modify_prot_commit);
arch/powerpc/mm/pgtable-radix.c +18 -0
index 931156069a81..14938186df5b 100644
@@ -1063,3 +1063,21 @@ void radix__ptep_set_access_flags(struct vm_area_struct *vma, pte_t *ptep,
 	}
 	/* See ptesync comment in radix__set_pte_at */
 }
+
+void radix__ptep_modify_prot_commit(struct vm_area_struct *vma,
+				    unsigned long addr, pte_t *ptep,
+				    pte_t old_pte, pte_t pte)
+{
+	struct mm_struct *mm = vma->vm_mm;
+
+	/*
+	 * To avoid NMMU hang while relaxing access we need to flush the tlb before
+	 * we set the new value. We need to do this only for radix, because hash
+	 * translation does flush when updating the linux pte.
+	 */
+	if (is_pte_rw_upgrade(pte_val(old_pte), pte_val(pte)) &&
+	    (atomic_read(&mm->context.copros) > 0))
+		flush_tlb_page(vma, addr);
+
+	set_pte_at(mm, addr, ptep, pte);
+}
Signature · 1 line
2.19.1
author
#4 lore raw

PATCH v2 4/5 mm/hugetlb: Add prot_modify_start/commit sequence for hugetlb update

In reply to Aneesh Kumar K.V
Signed-off-by Aneesh Kumar K.V <[email protected]>
---
 include/linux/hugetlb.h | 18 ++++++++++++++++++
 mm/hugetlb.c            |  8 +++++---
 2 files changed, 23 insertions(+), 3 deletions(-)
include/linux/hugetlb.h +18 -0
index 087fd5f48c91..e2a3b0c854eb 100644
@@ -543,6 +543,24 @@ static inline void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr
 	set_huge_pte_at(mm, addr, ptep, pte);
 }
 #endif
+
+#ifndef huge_ptep_modify_prot_start
+static inline pte_t huge_ptep_modify_prot_start(struct vm_area_struct *vma,
+						unsigned long addr, pte_t *ptep)
+{
+	return huge_ptep_get_and_clear(vma->vm_mm, addr, ptep);
+}
+#endif
+
+#ifndef huge_ptep_modify_prot_commit
+static inline void huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
+						unsigned long addr, pte_t *ptep,
+						pte_t old_pte, pte_t pte)
+{
+	set_huge_pte_at(vma->vm_mm, addr, ptep, pte);
+}
+#endif
+
 #else	/* CONFIG_HUGETLB_PAGE */
 struct hstate {};
 #define alloc_huge_page(v, a, r) NULL
mm/hugetlb.c +5 -3
index 7f2a28ab46d5..e5f5cda14f28 100644
@@ -4388,10 +4388,12 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
 			continue;
 		}
 		if (!huge_pte_none(pte)) {
-			pte = huge_ptep_get_and_clear(mm, address, ptep);
-			pte = pte_mkhuge(huge_pte_modify(pte, newprot));
+			pte_t old_pte;
+
+			old_pte = huge_ptep_modify_prot_start(vma, address, ptep);
+			pte = pte_mkhuge(huge_pte_modify(old_pte, newprot));
 			pte = arch_make_huge_pte(pte, vma, NULL, 0);
-			set_huge_pte_at(mm, address, ptep, pte);
+			huge_ptep_modify_prot_commit(vma, address, ptep, old_pte, pte);
 			pages++;
 		}
 		spin_unlock(ptl);
Signature · 1 line
2.19.1
maintainer
#5 lore raw

Re: [PATCH V2 4/5] mm/hugetlb: Add prot_modify_start/commit sequence for hugetlb update

Quoted 1 line · On Wed, 28 Nov 2018 20:04:37 +0530 "Aneesh Kumar K.V"…
Signed-off-by Aneesh Kumar K.V <[email protected]>

Some explanation of the motivation would be useful.

Quoted 10 lines
 include/linux/hugetlb.h | 18 ++++++++++++++++++
 mm/hugetlb.c            |  8 +++++---
 2 files changed, 23 insertions(+), 3 deletions(-)
include/linux/hugetlb.h +0 -0
index 087fd5f48c91..e2a3b0c854eb 100644
@@ -543,6 +543,24 @@ static inline void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr
 	set_huge_pte_at(mm, addr, ptep, pte);

include/linux/hugetlb.h static inline void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr · line 553

Quoted 10 lines
include/linux/hugetlb.h +8 -0
 }
 #endif
+
+#ifndef huge_ptep_modify_prot_start
+static inline pte_t huge_ptep_modify_prot_start(struct vm_area_struct *vma,
+						unsigned long addr, pte_t *ptep)
+{
+	return huge_ptep_get_and_clear(vma->vm_mm, addr, ptep);
+}
+#endif

#define huge_ptep_modify_prot_start huge_ptep_modify_prot_start

include/linux/hugetlb.h static inline void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr · line 562

Quoted 8 lines
include/linux/hugetlb.h +8 -0
+#ifndef huge_ptep_modify_prot_commit
+static inline void huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
+						unsigned long addr, pte_t *ptep,
+						pte_t old_pte, pte_t pte)
+{
+	set_huge_pte_at(vma->vm_mm, addr, ptep, pte);
+}
+#endif

#define huge_ptep_modify_prot_commit huge_ptep_modify_prot_commit

author
#6 lore raw

Re: [PATCH V2 4/5] mm/hugetlb: Add prot_modify_start/commit sequence for hugetlb update

Quoted 5 lines · Andrew Morton
Quoted 1 line · On Wed, 28 Nov 2018 20:04:37 +0530 "Aneesh Kumar K.V"…
Signed-off-by Aneesh Kumar K.V <[email protected]>

Some explanation of the motivation would be useful.

I will update the commit message.

Quoted 24 lines
Quoted 11 lines
  include/linux/hugetlb.h | 18 ++++++++++++++++++
  mm/hugetlb.c            |  8 +++++---
  2 files changed, 23 insertions(+), 3 deletions(-)
include/linux/hugetlb.h +0 -0
index 087fd5f48c91..e2a3b0c854eb 100644
@@ -543,6 +543,24 @@ static inline void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr
  	set_huge_pte_at(mm, addr, ptep, pte);

include/linux/hugetlb.h static inline void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr · line 553

Quoted 10 lines
include/linux/hugetlb.h +8 -0
  }
  #endif
+
+#ifndef huge_ptep_modify_prot_start
+static inline pte_t huge_ptep_modify_prot_start(struct vm_area_struct *vma,
+						unsigned long addr, pte_t *ptep)
+{
+	return huge_ptep_get_and_clear(vma->vm_mm, addr, ptep);
+}
+#endif

#define huge_ptep_modify_prot_start huge_ptep_modify_prot_start

Quoted 12 lines

include/linux/hugetlb.h static inline void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr · line 562

Quoted 8 lines
include/linux/hugetlb.h +8 -0
+#ifndef huge_ptep_modify_prot_commit
+static inline void huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
+						unsigned long addr, pte_t *ptep,
+						pte_t old_pte, pte_t pte)
+{
+	set_huge_pte_at(vma->vm_mm, addr, ptep, pte);
+}
+#endif

#define huge_ptep_modify_prot_commit huge_ptep_modify_prot_commit

Will update.

-aneesh

author
#7 lore raw

Re: [PATCH V2 4/5] mm/hugetlb: Add prot_modify_start/commit sequence for hugetlb update

Quoted 9 lines · Aneesh Kumar K.V
Quoted 5 lines · Andrew Morton
Quoted 1 line · On Wed, 28 Nov 2018 20:04:37 +0530 "Aneesh Kumar K.V"…
Signed-off-by Aneesh Kumar K.V <[email protected]>

Some explanation of the motivation would be useful.

I will update the commit message.

Is this good?

mm/hugetlb: Add prot_modify_start/commit sequence for hugetlb update

Architectures like ppc64 requires to do a conditional tlb flush based on the old and new value of pte. Follow the regular pte change protection sequence for hugetlb too. This allow the architectures to override the update sequence.

-aneesh

author
#8 lore raw

PATCH v2 5/5 arch/powerpc/mm/hugetlb: NestMMU workaround for hugetlb mprotect RW upgrade

In reply to Aneesh Kumar K.V

NestMMU requires us to mark the pte invalid and flush the tlb when we do a RW upgrade of pte. We fixed a variant of this in the fault path in commit

Fixes bd5050e38aec ("powerpc/mm/radix: Change pte relax sequence to handle nest MMU hang")
Signed-off-by Aneesh Kumar K.V <[email protected]>
---
 arch/powerpc/include/asm/book3s/64/hugetlb.h | 12 ++++++++
 arch/powerpc/mm/hugetlbpage-radix.c          | 17 ++++++++++++
 arch/powerpc/mm/hugetlbpage.c                | 29 ++++++++++++++++++++
 3 files changed, 58 insertions(+)
arch/powerpc/include/asm/book3s/64/hugetlb.h +12 -0
index 5b0177733994..66c1e4f88d65 100644
@@ -13,6 +13,10 @@ radix__hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 				unsigned long len, unsigned long pgoff,
 				unsigned long flags);
 
+extern void radix__huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
+						unsigned long addr, pte_t *ptep,
+						pte_t old_pte, pte_t pte);
+
 static inline int hstate_get_psize(struct hstate *hstate)
 {
 	unsigned long shift;

@@ -42,4 +46,12 @@ static inline bool gigantic_page_supported(void)
 /* hugepd entry valid bit */
 #define HUGEPD_VAL_BITS		(0x8000000000000000UL)
 
+#define huge_ptep_modify_prot_start huge_ptep_modify_prot_start
+extern pte_t huge_ptep_modify_prot_start(struct vm_area_struct *vma,
+					 unsigned long addr, pte_t *ptep);
+
+#define huge_ptep_modify_prot_commit huge_ptep_modify_prot_commit
+extern void huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
+					 unsigned long addr, pte_t *ptep,
+					 pte_t old_pte, pte_t new_pte);
 #endif
arch/powerpc/mm/hugetlbpage-radix.c +17 -0
index 2486bee0f93e..1f77d71e7708 100644
@@ -90,3 +90,20 @@ radix__hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 
 	return vm_unmapped_area(&info);
 }
+
+void radix__huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
+					 unsigned long addr, pte_t *ptep,
+					 pte_t old_pte, pte_t pte)
+{
+	struct mm_struct *mm = vma->vm_mm;
+
+	/*
+	 * To avoid NMMU hang while relaxing access we need to flush the tlb before
+	 * we set the new value.
+	 */
+	if (is_pte_rw_upgrade(pte_val(old_pte), pte_val(pte)) &&
+	    (atomic_read(&mm->context.copros) > 0))
+		flush_hugetlb_page(vma, addr);
+
+	set_huge_pte_at(vma->vm_mm, addr, ptep, pte);
+}
arch/powerpc/mm/hugetlbpage.c +29 -0
index 8cf035e68378..39d33a3d0dc6 100644
@@ -912,3 +912,32 @@ int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
 
 	return 1;
 }
+
+#ifdef CONFIG_PPC_BOOK3S_64
+pte_t huge_ptep_modify_prot_start(struct vm_area_struct *vma,
+				  unsigned long addr, pte_t *ptep)
+{
+	unsigned long pte_val;
+	/*
+	 * Clear the _PAGE_PRESENT so that no hardware parallel update is
+	 * possible. Also keep the pte_present true so that we don't take
+	 * wrong fault.
+	 */
+	pte_val = pte_update(vma->vm_mm, addr, ptep,
+			     _PAGE_PRESENT, _PAGE_INVALID, 1);
+
+	return __pte(pte_val);
+}
+EXPORT_SYMBOL(huge_ptep_modify_prot_start);
+
+void huge_ptep_modify_prot_commit(struct vm_area_struct *vma, unsigned long addr,
+				  pte_t *ptep, pte_t old_pte, pte_t pte)
+{
+
+	if (radix_enabled())
+		return radix__huge_ptep_modify_prot_commit(vma, addr, ptep,
+							   old_pte, pte);
+	set_huge_pte_at(vma->vm_mm, addr, ptep, pte);
+}
+EXPORT_SYMBOL(huge_ptep_modify_prot_commit);
+#endif
Signature · 1 line
2.19.1
maintainer
#9 lore raw
In reply to Aneesh Kumar K.V
Quoted 4 lines · On Wed, 28 Nov 2018 20:04:33 +0530 "Aneesh Kumar K.V"…

We can upgrade pte access (R -> RW transition) via mprotect. We need
to make sure we follow the recommended pte update sequence as outlined in
commit: bd5050e38aec ("powerpc/mm/radix: Change pte relax sequence to handle nest MMU hang") for such updates. This patch series do that.

The mm bits look (mostly) OK to me. I suggest all these be merged via the appropriate powerpc tree.