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* [PATCH v2 00/13] Convert x86 & arm64 to use generic page walk
@ 2019-02-21 11:34 Steven Price
  2019-02-21 11:34 ` [PATCH v2 01/13] arm64: mm: Add p?d_large() definitions Steven Price
                   ` (12 more replies)
  0 siblings, 13 replies; 31+ messages in thread
From: Steven Price @ 2019-02-21 11:34 UTC (permalink / raw)
  To: linux-mm
  Cc: Steven Price, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

Most architectures current have a debugfs file for dumping the kernel
page tables. Currently each architecture has to implement custom
functions for walking the page tables because the generic
walk_page_range() function is unable to walk the page tables used by the
kernel.

This series extends the capabilities of walk_page_range() so that it can
deal with the page tables of the kernel (which have no VMAs and can
contain larger huge pages than exist for user space). x86 and arm64 are
then converted to make use of walk_page_range() removing the custom page
table walkers.

Potentially future changes could unify the implementations of the
debugfs walkers further, moving the common functionality into common
code. This would require a common way of handling the effective
permissions (currently implemented only for x86) along with a per-arch
way of formatting the page table information for debugfs. One
immediate benefit would be getting the KASAN speed up optimisation in
arm64 (and other arches) which is currently only implemented for x86.

Changes since v1:
 * Added p4d_large() macro
 * Comments to explain p?d_large() macro semantics
 * Expanded comment for pte_hole() callback to explain mapping between
   depth and P?D
 * Handle folded page tables at all levels, so depth from pte_hole()
   ignores folding at any level (see real_depth() function in
   mm/pagewalk.c)

James Morse (2):
  arm64: mm: Add p?d_large() definitions
  mm: Add generic p?d_large() macros

Steven Price (11):
  x86/mm: Add p?d_large() definitions
  mm: pagewalk: Add p4d_entry() and pgd_entry()
  mm: pagewalk: Allow walking without vma
  mm: pagewalk: Add 'depth' parameter to pte_hole
  mm: pagewalk: Add test_p?d callbacks
  arm64: mm: Convert mm/dump.c to use walk_page_range()
  x86/mm: Point to struct seq_file from struct pg_state
  x86/mm+efi: Convert ptdump_walk_pgd_level() to take a mm_struct
  x86/mm: Convert ptdump_walk_pgd_level_debugfs() to take an mm_struct
  x86/mm: Convert ptdump_walk_pgd_level_core() to take an mm_struct
  x86: mm: Convert dump_pagetables to use walk_page_range

 arch/arm64/include/asm/pgtable.h |   2 +
 arch/arm64/mm/dump.c             | 108 +++++-----
 arch/x86/include/asm/pgtable.h   |   8 +-
 arch/x86/mm/debug_pagetables.c   |   8 +-
 arch/x86/mm/dump_pagetables.c    | 342 ++++++++++++++++---------------
 arch/x86/platform/efi/efi_32.c   |   2 +-
 arch/x86/platform/efi/efi_64.c   |   4 +-
 fs/proc/task_mmu.c               |   4 +-
 include/asm-generic/pgtable.h    |  19 ++
 include/linux/mm.h               |  26 ++-
 mm/hmm.c                         |   2 +-
 mm/migrate.c                     |   1 +
 mm/mincore.c                     |   1 +
 mm/pagewalk.c                    | 107 +++++++---
 14 files changed, 375 insertions(+), 259 deletions(-)

-- 
2.20.1


^ permalink raw reply	[flat|nested] 31+ messages in thread

* [PATCH v2 01/13] arm64: mm: Add p?d_large() definitions
  2019-02-21 11:34 [PATCH v2 00/13] Convert x86 & arm64 to use generic page walk Steven Price
@ 2019-02-21 11:34 ` Steven Price
  2019-02-21 13:52   ` Mark Rutland
  2019-02-21 11:34 ` [PATCH v2 02/13] x86/mm: " Steven Price
                   ` (11 subsequent siblings)
  12 siblings, 1 reply; 31+ messages in thread
From: Steven Price @ 2019-02-21 11:34 UTC (permalink / raw)
  To: linux-mm
  Cc: Steven Price, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

From: James Morse <james.morse@arm.com>

Exposing the pud/pgd levels of the page tables to walk_page_range() means
we may come across the exotic large mappings that come with large areas
of contiguous memory (such as the kernel's linear map).

Expose p?d_large() from each architecture to detect these large mappings.

arm64 already has these macros defined, but with a different name.
p?d_large() is used by s390, sparc and x86. Only arm/arm64 use p?d_sect().
Add a macro to allow both names.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/pgtable.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index de70c1eabf33..09d308921625 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -428,6 +428,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 				 PMD_TYPE_TABLE)
 #define pmd_sect(pmd)		((pmd_val(pmd) & PMD_TYPE_MASK) == \
 				 PMD_TYPE_SECT)
+#define pmd_large(x)		pmd_sect(x)
 
 #if defined(CONFIG_ARM64_64K_PAGES) || CONFIG_PGTABLE_LEVELS < 3
 #define pud_sect(pud)		(0)
@@ -435,6 +436,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 #else
 #define pud_sect(pud)		((pud_val(pud) & PUD_TYPE_MASK) == \
 				 PUD_TYPE_SECT)
+#define pud_large(x)		pud_sect(x)
 #define pud_table(pud)		((pud_val(pud) & PUD_TYPE_MASK) == \
 				 PUD_TYPE_TABLE)
 #endif
-- 
2.20.1


^ permalink raw reply	[flat|nested] 31+ messages in thread

* [PATCH v2 02/13] x86/mm: Add p?d_large() definitions
  2019-02-21 11:34 [PATCH v2 00/13] Convert x86 & arm64 to use generic page walk Steven Price
  2019-02-21 11:34 ` [PATCH v2 01/13] arm64: mm: Add p?d_large() definitions Steven Price
@ 2019-02-21 11:34 ` Steven Price
  2019-02-21 14:21   ` Kirill A. Shutemov
  2019-02-21 11:34 ` [PATCH v2 03/13] mm: Add generic p?d_large() macros Steven Price
                   ` (10 subsequent siblings)
  12 siblings, 1 reply; 31+ messages in thread
From: Steven Price @ 2019-02-21 11:34 UTC (permalink / raw)
  To: linux-mm
  Cc: Steven Price, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

Exposing the pud/pgd levels of the page tables to walk_page_range() means
we may come across the exotic large mappings that come with large areas
of contiguous memory (such as the kernel's linear map).

Expose p?d_large() from each architecture to detect these large mappings.

x86 already has these defined as inline functions, add a macro of the
same name so we don't end up with the generic version too.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/x86/include/asm/pgtable.h | 3 +++
 arch/x86/mm/dump_pagetables.c  | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 2779ace16d23..3695f6acb6af 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -234,6 +234,7 @@ static inline int pmd_large(pmd_t pte)
 {
 	return pmd_flags(pte) & _PAGE_PSE;
 }
+#define pmd_large(x)	pmd_large(x)
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static inline int pmd_trans_huge(pmd_t pmd)
@@ -873,6 +874,7 @@ static inline int pud_large(pud_t pud)
 	return 0;
 }
 #endif	/* CONFIG_PGTABLE_LEVELS > 2 */
+#define pud_large(x)	pud_large(x)
 
 static inline unsigned long pud_index(unsigned long address)
 {
@@ -1214,6 +1216,7 @@ static inline bool pgdp_maps_userspace(void *__ptr)
 }
 
 static inline int pgd_large(pgd_t pgd) { return 0; }
+#define pgd_large(x)	pgd_large(x)
 
 #ifdef CONFIG_PAGE_TABLE_ISOLATION
 /*
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index e3cdc85ce5b6..cf37abc0f58a 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -432,6 +432,7 @@ static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr,
 
 #else
 #define walk_pmd_level(m,s,a,e,p) walk_pte_level(m,s,__pmd(pud_val(a)),e,p)
+#undef pud_large
 #define pud_large(a) pmd_large(__pmd(pud_val(a)))
 #define pud_none(a)  pmd_none(__pmd(pud_val(a)))
 #endif
@@ -469,6 +470,7 @@ static void walk_pud_level(struct seq_file *m, struct pg_state *st, p4d_t addr,
 
 #else
 #define walk_pud_level(m,s,a,e,p) walk_pmd_level(m,s,__pud(p4d_val(a)),e,p)
+#undef p4d_large
 #define p4d_large(a) pud_large(__pud(p4d_val(a)))
 #define p4d_none(a)  pud_none(__pud(p4d_val(a)))
 #endif
@@ -503,6 +505,7 @@ static void walk_p4d_level(struct seq_file *m, struct pg_state *st, pgd_t addr,
 	}
 }
 
+#undef pgd_large
 #define pgd_large(a) (pgtable_l5_enabled() ? pgd_large(a) : p4d_large(__p4d(pgd_val(a))))
 #define pgd_none(a)  (pgtable_l5_enabled() ? pgd_none(a) : p4d_none(__p4d(pgd_val(a))))
 
-- 
2.20.1


^ permalink raw reply	[flat|nested] 31+ messages in thread

* [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-02-21 11:34 [PATCH v2 00/13] Convert x86 & arm64 to use generic page walk Steven Price
  2019-02-21 11:34 ` [PATCH v2 01/13] arm64: mm: Add p?d_large() definitions Steven Price
  2019-02-21 11:34 ` [PATCH v2 02/13] x86/mm: " Steven Price
@ 2019-02-21 11:34 ` Steven Price
  2019-02-21 13:41   ` Mark Rutland
  2019-02-21 14:28   ` Kirill A. Shutemov
  2019-02-21 11:34 ` [PATCH v2 04/13] mm: pagewalk: Add p4d_entry() and pgd_entry() Steven Price
                   ` (9 subsequent siblings)
  12 siblings, 2 replies; 31+ messages in thread
From: Steven Price @ 2019-02-21 11:34 UTC (permalink / raw)
  To: linux-mm
  Cc: Steven Price, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

From: James Morse <james.morse@arm.com>

Exposing the pud/pgd levels of the page tables to walk_page_range() means
we may come across the exotic large mappings that come with large areas
of contiguous memory (such as the kernel's linear map).

For architectures that don't provide p?d_large() macros, provided a
does nothing default.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
 include/asm-generic/pgtable.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 05e61e6c843f..f0de24100ac6 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -1186,4 +1186,23 @@ static inline bool arch_has_pfn_modify_check(void)
 #define mm_pmd_folded(mm)	__is_defined(__PAGETABLE_PMD_FOLDED)
 #endif
 
+/*
+ * p?d_large() - true if this entry is a final mapping to a physical address.
+ * This differs from p?d_huge() by the fact that they are always available (if
+ * the architecture supports large pages at the appropriate level) even
+ * if CONFIG_HUGETLB_PAGE is not defined.
+ */
+#ifndef pgd_large
+#define pgd_large(x)	0
+#endif
+#ifndef p4d_large
+#define p4d_large(x)	0
+#endif
+#ifndef pud_large
+#define pud_large(x)	0
+#endif
+#ifndef pmd_large
+#define pmd_large(x)	0
+#endif
+
 #endif /* _ASM_GENERIC_PGTABLE_H */
-- 
2.20.1


^ permalink raw reply	[flat|nested] 31+ messages in thread

* [PATCH v2 04/13] mm: pagewalk: Add p4d_entry() and pgd_entry()
  2019-02-21 11:34 [PATCH v2 00/13] Convert x86 & arm64 to use generic page walk Steven Price
                   ` (2 preceding siblings ...)
  2019-02-21 11:34 ` [PATCH v2 03/13] mm: Add generic p?d_large() macros Steven Price
@ 2019-02-21 11:34 ` Steven Price
  2019-02-21 11:34 ` [PATCH v2 05/13] mm: pagewalk: Allow walking without vma Steven Price
                   ` (8 subsequent siblings)
  12 siblings, 0 replies; 31+ messages in thread
From: Steven Price @ 2019-02-21 11:34 UTC (permalink / raw)
  To: linux-mm
  Cc: Steven Price, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

pgd_entry() and pud_entry() were removed by commit 0b1fbfe50006c410
("mm/pagewalk: remove pgd_entry() and pud_entry()") because there were
no users. We're about to add users so reintroduce them, along with
p4d_entry() as we now have 5 levels of tables.

Note that commit a00cc7d9dd93d66a ("mm, x86: add support for
PUD-sized transparent hugepages") already re-added pud_entry() but with
different semantics to the other callbacks. Since there have never
been upstream users of this, revert the semantics back to match the
other callbacks. This means pud_entry() is called for all entries, not
just transparent huge pages.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 include/linux/mm.h |  9 ++++++---
 mm/pagewalk.c      | 27 ++++++++++++++++-----------
 2 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 80bb6408fe73..1a4b1615d012 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1412,10 +1412,9 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
 
 /**
  * mm_walk - callbacks for walk_page_range
+ * @pgd_entry: if set, called for each non-empty PGD (top-level) entry
+ * @p4d_entry: if set, called for each non-empty P4D (1st-level) entry
  * @pud_entry: if set, called for each non-empty PUD (2nd-level) entry
- *	       this handler should only handle pud_trans_huge() puds.
- *	       the pmd_entry or pte_entry callbacks will be used for
- *	       regular PUDs.
  * @pmd_entry: if set, called for each non-empty PMD (3rd-level) entry
  *	       this handler is required to be able to handle
  *	       pmd_trans_huge() pmds.  They may simply choose to
@@ -1435,6 +1434,10 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
  * (see the comment on walk_page_range() for more details)
  */
 struct mm_walk {
+	int (*pgd_entry)(pgd_t *pgd, unsigned long addr,
+			 unsigned long next, struct mm_walk *walk);
+	int (*p4d_entry)(p4d_t *p4d, unsigned long addr,
+			 unsigned long next, struct mm_walk *walk);
 	int (*pud_entry)(pud_t *pud, unsigned long addr,
 			 unsigned long next, struct mm_walk *walk);
 	int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index c3084ff2569d..98373a9f88b8 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -90,15 +90,9 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
 		}
 
 		if (walk->pud_entry) {
-			spinlock_t *ptl = pud_trans_huge_lock(pud, walk->vma);
-
-			if (ptl) {
-				err = walk->pud_entry(pud, addr, next, walk);
-				spin_unlock(ptl);
-				if (err)
-					break;
-				continue;
-			}
+			err = walk->pud_entry(pud, addr, next, walk);
+			if (err)
+				break;
 		}
 
 		split_huge_pud(walk->vma, pud, addr);
@@ -131,7 +125,12 @@ static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
 				break;
 			continue;
 		}
-		if (walk->pmd_entry || walk->pte_entry)
+		if (walk->p4d_entry) {
+			err = walk->p4d_entry(p4d, addr, next, walk);
+			if (err)
+				break;
+		}
+		if (walk->pud_entry || walk->pmd_entry || walk->pte_entry)
 			err = walk_pud_range(p4d, addr, next, walk);
 		if (err)
 			break;
@@ -157,7 +156,13 @@ static int walk_pgd_range(unsigned long addr, unsigned long end,
 				break;
 			continue;
 		}
-		if (walk->pmd_entry || walk->pte_entry)
+		if (walk->pgd_entry) {
+			err = walk->pgd_entry(pgd, addr, next, walk);
+			if (err)
+				break;
+		}
+		if (walk->p4d_entry || walk->pud_entry || walk->pmd_entry ||
+				walk->pte_entry)
 			err = walk_p4d_range(pgd, addr, next, walk);
 		if (err)
 			break;
-- 
2.20.1


^ permalink raw reply	[flat|nested] 31+ messages in thread

* [PATCH v2 05/13] mm: pagewalk: Allow walking without vma
  2019-02-21 11:34 [PATCH v2 00/13] Convert x86 & arm64 to use generic page walk Steven Price
                   ` (3 preceding siblings ...)
  2019-02-21 11:34 ` [PATCH v2 04/13] mm: pagewalk: Add p4d_entry() and pgd_entry() Steven Price
@ 2019-02-21 11:34 ` Steven Price
  2019-02-21 11:34 ` [PATCH v2 06/13] mm: pagewalk: Add 'depth' parameter to pte_hole Steven Price
                   ` (7 subsequent siblings)
  12 siblings, 0 replies; 31+ messages in thread
From: Steven Price @ 2019-02-21 11:34 UTC (permalink / raw)
  To: linux-mm
  Cc: Steven Price, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

Since 48684a65b4e3: "mm: pagewalk: fix misbehavior of walk_page_range
for vma(VM_PFNMAP)", page_table_walk() will report any kernel area as
a hole, because it lacks a vma.

This means each arch has re-implemented page table walking when needed,
for example in the per-arch ptdump walker.

Remove the requirement to have a vma except when trying to split huge
pages.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 mm/pagewalk.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 98373a9f88b8..dac0c848b458 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -36,7 +36,7 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 	do {
 again:
 		next = pmd_addr_end(addr, end);
-		if (pmd_none(*pmd) || !walk->vma) {
+		if (pmd_none(*pmd)) {
 			if (walk->pte_hole)
 				err = walk->pte_hole(addr, next, walk);
 			if (err)
@@ -59,9 +59,14 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 		if (!walk->pte_entry)
 			continue;
 
-		split_huge_pmd(walk->vma, pmd, addr);
-		if (pmd_trans_unstable(pmd))
-			goto again;
+		if (walk->vma) {
+			split_huge_pmd(walk->vma, pmd, addr);
+			if (pmd_trans_unstable(pmd))
+				goto again;
+		} else if (pmd_large(*pmd)) {
+			continue;
+		}
+
 		err = walk_pte_range(pmd, addr, next, walk);
 		if (err)
 			break;
@@ -81,7 +86,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
 	do {
  again:
 		next = pud_addr_end(addr, end);
-		if (pud_none(*pud) || !walk->vma) {
+		if (pud_none(*pud)) {
 			if (walk->pte_hole)
 				err = walk->pte_hole(addr, next, walk);
 			if (err)
@@ -95,9 +100,13 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
 				break;
 		}
 
-		split_huge_pud(walk->vma, pud, addr);
-		if (pud_none(*pud))
-			goto again;
+		if (walk->vma) {
+			split_huge_pud(walk->vma, pud, addr);
+			if (pud_none(*pud))
+				goto again;
+		} else if (pud_large(*pud)) {
+			continue;
+		}
 
 		if (walk->pmd_entry || walk->pte_entry)
 			err = walk_pmd_range(pud, addr, next, walk);
-- 
2.20.1


^ permalink raw reply	[flat|nested] 31+ messages in thread

* [PATCH v2 06/13] mm: pagewalk: Add 'depth' parameter to pte_hole
  2019-02-21 11:34 [PATCH v2 00/13] Convert x86 & arm64 to use generic page walk Steven Price
                   ` (4 preceding siblings ...)
  2019-02-21 11:34 ` [PATCH v2 05/13] mm: pagewalk: Allow walking without vma Steven Price
@ 2019-02-21 11:34 ` Steven Price
  2019-02-21 11:34 ` [PATCH v2 07/13] mm: pagewalk: Add test_p?d callbacks Steven Price
                   ` (6 subsequent siblings)
  12 siblings, 0 replies; 31+ messages in thread
From: Steven Price @ 2019-02-21 11:34 UTC (permalink / raw)
  To: linux-mm
  Cc: Steven Price, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

The pte_hole() callback is called at multiple levels of the page tables.
Code dumping the kernel page tables needs to know what at what depth
the missing entry is. Add this is an extra parameter to pte_hole().
When the depth isn't know (e.g. processing a vma) then -1 is passed.

The depth that is reported is the actual level where the entry is
missing (ignoring any folding that is in place), i.e. any levels where
PTRS_PER_P?D is set to 1 are ignored.

Note that depth starts at 0 for a PGD so that PUD/PMD/PTE retain their
natural numbers as levels 2/3/4.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 fs/proc/task_mmu.c |  4 ++--
 include/linux/mm.h |  6 ++++--
 mm/hmm.c           |  2 +-
 mm/migrate.c       |  1 +
 mm/mincore.c       |  1 +
 mm/pagewalk.c      | 31 +++++++++++++++++++++++++------
 6 files changed, 34 insertions(+), 11 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index f0ec9edab2f3..91131cd4e9e0 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -474,7 +474,7 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
 
 #ifdef CONFIG_SHMEM
 static int smaps_pte_hole(unsigned long addr, unsigned long end,
-		struct mm_walk *walk)
+			  __always_unused int depth, struct mm_walk *walk)
 {
 	struct mem_size_stats *mss = walk->private;
 
@@ -1203,7 +1203,7 @@ static int add_to_pagemap(unsigned long addr, pagemap_entry_t *pme,
 }
 
 static int pagemap_pte_hole(unsigned long start, unsigned long end,
-				struct mm_walk *walk)
+			    __always_unused int depth, struct mm_walk *walk)
 {
 	struct pagemapread *pm = walk->private;
 	unsigned long addr = start;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1a4b1615d012..4ae3634a9118 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1420,7 +1420,9 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
  *	       pmd_trans_huge() pmds.  They may simply choose to
  *	       split_huge_page() instead of handling it explicitly.
  * @pte_entry: if set, called for each non-empty PTE (4th-level) entry
- * @pte_hole: if set, called for each hole at all levels
+ * @pte_hole: if set, called for each hole at all levels,
+ *            depth is -1 if not known, 0:PGD, 1:P4D, 2:PUD, 3:PMD, 4:PTE
+ *            any depths where PTRS_PER_P?D is equal to 1 are skipped
  * @hugetlb_entry: if set, called for each hugetlb entry
  * @test_walk: caller specific callback function to determine whether
  *             we walk over the current vma or not. Returning 0
@@ -1445,7 +1447,7 @@ struct mm_walk {
 	int (*pte_entry)(pte_t *pte, unsigned long addr,
 			 unsigned long next, struct mm_walk *walk);
 	int (*pte_hole)(unsigned long addr, unsigned long next,
-			struct mm_walk *walk);
+			int depth, struct mm_walk *walk);
 	int (*hugetlb_entry)(pte_t *pte, unsigned long hmask,
 			     unsigned long addr, unsigned long next,
 			     struct mm_walk *walk);
diff --git a/mm/hmm.c b/mm/hmm.c
index a04e4b810610..e3e6b8fda437 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -440,7 +440,7 @@ static void hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
 }
 
 static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
-			     struct mm_walk *walk)
+			     __always_unused int depth, struct mm_walk *walk)
 {
 	struct hmm_vma_walk *hmm_vma_walk = walk->private;
 	struct hmm_range *range = hmm_vma_walk->range;
diff --git a/mm/migrate.c b/mm/migrate.c
index d4fd680be3b0..8b62a9fecb5c 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2121,6 +2121,7 @@ struct migrate_vma {
 
 static int migrate_vma_collect_hole(unsigned long start,
 				    unsigned long end,
+				    __always_unused int depth,
 				    struct mm_walk *walk)
 {
 	struct migrate_vma *migrate = walk->private;
diff --git a/mm/mincore.c b/mm/mincore.c
index 218099b5ed31..c4edbc688241 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -104,6 +104,7 @@ static int __mincore_unmapped_range(unsigned long addr, unsigned long end,
 }
 
 static int mincore_unmapped_range(unsigned long addr, unsigned long end,
+				   __always_unused int depth,
 				   struct mm_walk *walk)
 {
 	walk->private += __mincore_unmapped_range(addr, end,
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index dac0c848b458..57946bcd810c 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -4,6 +4,22 @@
 #include <linux/sched.h>
 #include <linux/hugetlb.h>
 
+/*
+ * We want to know the real level where a entry is located ignoring any
+ * folding of levels which may be happening. For example if p4d is folded then
+ * a missing entry found at level 1 (p4d) is actually at level 0 (pgd).
+ */
+static int real_depth(int depth)
+{
+	if (depth == 3 && PTRS_PER_PMD == 1)
+		depth = 2;
+	if (depth == 2 && PTRS_PER_PUD == 1)
+		depth = 1;
+	if (depth == 1 && PTRS_PER_P4D == 1)
+		depth = 0;
+	return depth;
+}
+
 static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 			  struct mm_walk *walk)
 {
@@ -31,6 +47,7 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 	pmd_t *pmd;
 	unsigned long next;
 	int err = 0;
+	int depth = real_depth(3);
 
 	pmd = pmd_offset(pud, addr);
 	do {
@@ -38,7 +55,7 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 		next = pmd_addr_end(addr, end);
 		if (pmd_none(*pmd)) {
 			if (walk->pte_hole)
-				err = walk->pte_hole(addr, next, walk);
+				err = walk->pte_hole(addr, next, depth, walk);
 			if (err)
 				break;
 			continue;
@@ -81,6 +98,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
 	pud_t *pud;
 	unsigned long next;
 	int err = 0;
+	int depth = real_depth(2);
 
 	pud = pud_offset(p4d, addr);
 	do {
@@ -88,7 +106,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
 		next = pud_addr_end(addr, end);
 		if (pud_none(*pud)) {
 			if (walk->pte_hole)
-				err = walk->pte_hole(addr, next, walk);
+				err = walk->pte_hole(addr, next, depth, walk);
 			if (err)
 				break;
 			continue;
@@ -123,13 +141,14 @@ static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
 	p4d_t *p4d;
 	unsigned long next;
 	int err = 0;
+	int depth = real_depth(1);
 
 	p4d = p4d_offset(pgd, addr);
 	do {
 		next = p4d_addr_end(addr, end);
 		if (p4d_none_or_clear_bad(p4d)) {
 			if (walk->pte_hole)
-				err = walk->pte_hole(addr, next, walk);
+				err = walk->pte_hole(addr, next, depth, walk);
 			if (err)
 				break;
 			continue;
@@ -160,7 +179,7 @@ static int walk_pgd_range(unsigned long addr, unsigned long end,
 		next = pgd_addr_end(addr, end);
 		if (pgd_none_or_clear_bad(pgd)) {
 			if (walk->pte_hole)
-				err = walk->pte_hole(addr, next, walk);
+				err = walk->pte_hole(addr, next, 0, walk);
 			if (err)
 				break;
 			continue;
@@ -206,7 +225,7 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
 		if (pte)
 			err = walk->hugetlb_entry(pte, hmask, addr, next, walk);
 		else if (walk->pte_hole)
-			err = walk->pte_hole(addr, next, walk);
+			err = walk->pte_hole(addr, next, -1, walk);
 
 		if (err)
 			break;
@@ -249,7 +268,7 @@ static int walk_page_test(unsigned long start, unsigned long end,
 	if (vma->vm_flags & VM_PFNMAP) {
 		int err = 1;
 		if (walk->pte_hole)
-			err = walk->pte_hole(start, end, walk);
+			err = walk->pte_hole(start, end, -1, walk);
 		return err ? err : 1;
 	}
 	return 0;
-- 
2.20.1


^ permalink raw reply	[flat|nested] 31+ messages in thread

* [PATCH v2 07/13] mm: pagewalk: Add test_p?d callbacks
  2019-02-21 11:34 [PATCH v2 00/13] Convert x86 & arm64 to use generic page walk Steven Price
                   ` (5 preceding siblings ...)
  2019-02-21 11:34 ` [PATCH v2 06/13] mm: pagewalk: Add 'depth' parameter to pte_hole Steven Price
@ 2019-02-21 11:34 ` Steven Price
  2019-02-21 11:34 ` [PATCH v2 08/13] arm64: mm: Convert mm/dump.c to use walk_page_range() Steven Price
                   ` (5 subsequent siblings)
  12 siblings, 0 replies; 31+ messages in thread
From: Steven Price @ 2019-02-21 11:34 UTC (permalink / raw)
  To: linux-mm
  Cc: Steven Price, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

It is useful to be able to skip parts of the page table tree even when
walking without VMAs. Add test_p?d callbacks similar to test_walk but
which are called just before a table at that level is walked. If the
callback returns non-zero then the entire table is skipped.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 include/linux/mm.h | 11 +++++++++++
 mm/pagewalk.c      | 24 ++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 4ae3634a9118..581f31c6b6d9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1429,6 +1429,11 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
  *             value means "do page table walk over the current vma,"
  *             and a negative one means "abort current page table walk
  *             right now." 1 means "skip the current vma."
+ * @test_pmd:  similar to test_walk(), but called for every pmd.
+ * @test_pud:  similar to test_walk(), but called for every pud.
+ * @test_p4d:  similar to test_walk(), but called for every p4d.
+ *             Returning 0 means walk this part of the page tables,
+ *             returning 1 means to skip this range.
  * @mm:        mm_struct representing the target process of page table walk
  * @vma:       vma currently walked (NULL if walking outside vmas)
  * @private:   private data for callbacks' usage
@@ -1453,6 +1458,12 @@ struct mm_walk {
 			     struct mm_walk *walk);
 	int (*test_walk)(unsigned long addr, unsigned long next,
 			struct mm_walk *walk);
+	int (*test_pmd)(unsigned long addr, unsigned long next,
+			pmd_t *pmd_start, struct mm_walk *walk);
+	int (*test_pud)(unsigned long addr, unsigned long next,
+			pud_t *pud_start, struct mm_walk *walk);
+	int (*test_p4d)(unsigned long addr, unsigned long next,
+			p4d_t *p4d_start, struct mm_walk *walk);
 	struct mm_struct *mm;
 	struct vm_area_struct *vma;
 	void *private;
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 57946bcd810c..ff2fc8490435 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -49,6 +49,14 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 	int err = 0;
 	int depth = real_depth(3);
 
+	if (walk->test_pmd) {
+		err = walk->test_pmd(addr, end, pmd_offset(pud, 0), walk);
+		if (err < 0)
+			return err;
+		if (err > 0)
+			return 0;
+	}
+
 	pmd = pmd_offset(pud, addr);
 	do {
 again:
@@ -100,6 +108,14 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
 	int err = 0;
 	int depth = real_depth(2);
 
+	if (walk->test_pud) {
+		err = walk->test_pud(addr, end, pud_offset(p4d, 0), walk);
+		if (err < 0)
+			return err;
+		if (err > 0)
+			return 0;
+	}
+
 	pud = pud_offset(p4d, addr);
 	do {
  again:
@@ -143,6 +159,14 @@ static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
 	int err = 0;
 	int depth = real_depth(1);
 
+	if (walk->test_p4d) {
+		err = walk->test_p4d(addr, end, p4d_offset(pgd, 0), walk);
+		if (err < 0)
+			return err;
+		if (err > 0)
+			return 0;
+	}
+
 	p4d = p4d_offset(pgd, addr);
 	do {
 		next = p4d_addr_end(addr, end);
-- 
2.20.1


^ permalink raw reply	[flat|nested] 31+ messages in thread

* [PATCH v2 08/13] arm64: mm: Convert mm/dump.c to use walk_page_range()
  2019-02-21 11:34 [PATCH v2 00/13] Convert x86 & arm64 to use generic page walk Steven Price
                   ` (6 preceding siblings ...)
  2019-02-21 11:34 ` [PATCH v2 07/13] mm: pagewalk: Add test_p?d callbacks Steven Price
@ 2019-02-21 11:34 ` Steven Price
  2019-02-21 11:34 ` [PATCH v2 09/13] x86/mm: Point to struct seq_file from struct pg_state Steven Price
                   ` (4 subsequent siblings)
  12 siblings, 0 replies; 31+ messages in thread
From: Steven Price @ 2019-02-21 11:34 UTC (permalink / raw)
  To: linux-mm
  Cc: Steven Price, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

Now walk_page_range() can walk kernel page tables, we can switch the
arm64 ptdump code over to using it, simplifying the code.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/mm/dump.c | 108 +++++++++++++++++++++----------------------
 1 file changed, 53 insertions(+), 55 deletions(-)

diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
index 99bb8facb5cb..ee0bc1441dd0 100644
--- a/arch/arm64/mm/dump.c
+++ b/arch/arm64/mm/dump.c
@@ -286,73 +286,71 @@ static void note_page(struct pg_state *st, unsigned long addr, unsigned level,
 
 }
 
-static void walk_pte(struct pg_state *st, pmd_t *pmdp, unsigned long start,
-		     unsigned long end)
+static int pud_entry(pud_t *pud, unsigned long addr,
+		unsigned long next, struct mm_walk *walk)
 {
-	unsigned long addr = start;
-	pte_t *ptep = pte_offset_kernel(pmdp, start);
+	struct pg_state *st = walk->private;
+	pud_t val = READ_ONCE(*pud);
 
-	do {
-		note_page(st, addr, 4, READ_ONCE(pte_val(*ptep)));
-	} while (ptep++, addr += PAGE_SIZE, addr != end);
+	if (pud_table(val))
+		return 0;
+
+	note_page(st, addr, 2, pud_val(val));
+
+	return 0;
 }
 
-static void walk_pmd(struct pg_state *st, pud_t *pudp, unsigned long start,
-		     unsigned long end)
+static int pmd_entry(pmd_t *pmd, unsigned long addr,
+		unsigned long next, struct mm_walk *walk)
 {
-	unsigned long next, addr = start;
-	pmd_t *pmdp = pmd_offset(pudp, start);
-
-	do {
-		pmd_t pmd = READ_ONCE(*pmdp);
-		next = pmd_addr_end(addr, end);
-
-		if (pmd_none(pmd) || pmd_sect(pmd)) {
-			note_page(st, addr, 3, pmd_val(pmd));
-		} else {
-			BUG_ON(pmd_bad(pmd));
-			walk_pte(st, pmdp, addr, next);
-		}
-	} while (pmdp++, addr = next, addr != end);
+	struct pg_state *st = walk->private;
+	pmd_t val = READ_ONCE(*pmd);
+
+	if (pmd_table(val))
+		return 0;
+
+	note_page(st, addr, 3, pmd_val(val));
+
+	return 0;
 }
 
-static void walk_pud(struct pg_state *st, pgd_t *pgdp, unsigned long start,
-		     unsigned long end)
+static int pte_entry(pte_t *pte, unsigned long addr,
+		unsigned long next, struct mm_walk *walk)
 {
-	unsigned long next, addr = start;
-	pud_t *pudp = pud_offset(pgdp, start);
-
-	do {
-		pud_t pud = READ_ONCE(*pudp);
-		next = pud_addr_end(addr, end);
-
-		if (pud_none(pud) || pud_sect(pud)) {
-			note_page(st, addr, 2, pud_val(pud));
-		} else {
-			BUG_ON(pud_bad(pud));
-			walk_pmd(st, pudp, addr, next);
-		}
-	} while (pudp++, addr = next, addr != end);
+	struct pg_state *st = walk->private;
+	pte_t val = READ_ONCE(*pte);
+
+	note_page(st, addr, 4, pte_val(val));
+
+	return 0;
+}
+
+static int pte_hole(unsigned long addr, unsigned long next, int depth,
+		struct mm_walk *walk)
+{
+	struct pg_state *st = walk->private;
+
+	note_page(st, addr, depth+1, 0);
+
+	return 0;
 }
 
 static void walk_pgd(struct pg_state *st, struct mm_struct *mm,
-		     unsigned long start)
+		unsigned long start)
 {
-	unsigned long end = (start < TASK_SIZE_64) ? TASK_SIZE_64 : 0;
-	unsigned long next, addr = start;
-	pgd_t *pgdp = pgd_offset(mm, start);
-
-	do {
-		pgd_t pgd = READ_ONCE(*pgdp);
-		next = pgd_addr_end(addr, end);
-
-		if (pgd_none(pgd)) {
-			note_page(st, addr, 1, pgd_val(pgd));
-		} else {
-			BUG_ON(pgd_bad(pgd));
-			walk_pud(st, pgdp, addr, next);
-		}
-	} while (pgdp++, addr = next, addr != end);
+	struct mm_walk walk = {
+		.mm = mm,
+		.private = st,
+		.pud_entry = pud_entry,
+		.pmd_entry = pmd_entry,
+		.pte_entry = pte_entry,
+		.pte_hole = pte_hole
+	};
+	down_read(&mm->mmap_sem);
+	walk_page_range(start, start | (((unsigned long)PTRS_PER_PGD <<
+					 PGDIR_SHIFT) - 1),
+			&walk);
+	up_read(&mm->mmap_sem);
 }
 
 void ptdump_walk_pgd(struct seq_file *m, struct ptdump_info *info)
-- 
2.20.1


^ permalink raw reply	[flat|nested] 31+ messages in thread

* [PATCH v2 09/13] x86/mm: Point to struct seq_file from struct pg_state
  2019-02-21 11:34 [PATCH v2 00/13] Convert x86 & arm64 to use generic page walk Steven Price
                   ` (7 preceding siblings ...)
  2019-02-21 11:34 ` [PATCH v2 08/13] arm64: mm: Convert mm/dump.c to use walk_page_range() Steven Price
@ 2019-02-21 11:34 ` Steven Price
  2019-02-21 11:34 ` [PATCH v2 10/13] x86/mm+efi: Convert ptdump_walk_pgd_level() to take a mm_struct Steven Price
                   ` (3 subsequent siblings)
  12 siblings, 0 replies; 31+ messages in thread
From: Steven Price @ 2019-02-21 11:34 UTC (permalink / raw)
  To: linux-mm
  Cc: Steven Price, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

mm/dump_pagetables.c passes both struct seq_file and struct pg_state
down the chain of walk_*_level() functions to be passed to note_page().
Instead place the struct seq_file in struct pg_state and access it from
struct pg_state (which is private to this file) in note_page().

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/x86/mm/dump_pagetables.c | 69 ++++++++++++++++++-----------------
 1 file changed, 35 insertions(+), 34 deletions(-)

diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index cf37abc0f58a..b1b86157d456 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -40,6 +40,7 @@ struct pg_state {
 	bool to_dmesg;
 	bool check_wx;
 	unsigned long wx_pages;
+	struct seq_file *seq;
 };
 
 struct addr_marker {
@@ -268,11 +269,12 @@ static void note_wx(struct pg_state *st)
  * of PTE entries; the next one is different so we need to
  * print what we collected so far.
  */
-static void note_page(struct seq_file *m, struct pg_state *st,
-		      pgprot_t new_prot, pgprotval_t new_eff, int level)
+static void note_page(struct pg_state *st, pgprot_t new_prot,
+		      pgprotval_t new_eff, int level)
 {
 	pgprotval_t prot, cur, eff;
 	static const char units[] = "BKMGTPE";
+	struct seq_file *m = st->seq;
 
 	/*
 	 * If we have a "break" in the series, we need to flush the state that
@@ -357,8 +359,8 @@ static inline pgprotval_t effective_prot(pgprotval_t prot1, pgprotval_t prot2)
 	       ((prot1 | prot2) & _PAGE_NX);
 }
 
-static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
-			   pgprotval_t eff_in, unsigned long P)
+static void walk_pte_level(struct pg_state *st, pmd_t addr, pgprotval_t eff_in,
+			   unsigned long P)
 {
 	int i;
 	pte_t *pte;
@@ -369,7 +371,7 @@ static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
 		pte = pte_offset_map(&addr, st->current_address);
 		prot = pte_flags(*pte);
 		eff = effective_prot(eff_in, prot);
-		note_page(m, st, __pgprot(prot), eff, 5);
+		note_page(st, __pgprot(prot), eff, 5);
 		pte_unmap(pte);
 	}
 }
@@ -382,22 +384,20 @@ static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
  * us dozens of seconds (minutes for 5-level config) while checking for
  * W+X mapping or reading kernel_page_tables debugfs file.
  */
-static inline bool kasan_page_table(struct seq_file *m, struct pg_state *st,
-				void *pt)
+static inline bool kasan_page_table(struct pg_state *st, void *pt)
 {
 	if (__pa(pt) == __pa(kasan_early_shadow_pmd) ||
 	    (pgtable_l5_enabled() &&
 			__pa(pt) == __pa(kasan_early_shadow_p4d)) ||
 	    __pa(pt) == __pa(kasan_early_shadow_pud)) {
 		pgprotval_t prot = pte_flags(kasan_early_shadow_pte[0]);
-		note_page(m, st, __pgprot(prot), 0, 5);
+		note_page(st, __pgprot(prot), 0, 5);
 		return true;
 	}
 	return false;
 }
 #else
-static inline bool kasan_page_table(struct seq_file *m, struct pg_state *st,
-				void *pt)
+static inline bool kasan_page_table(struct pg_state *st, void *pt)
 {
 	return false;
 }
@@ -405,7 +405,7 @@ static inline bool kasan_page_table(struct seq_file *m, struct pg_state *st,
 
 #if PTRS_PER_PMD > 1
 
-static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr,
+static void walk_pmd_level(struct pg_state *st, pud_t addr,
 			   pgprotval_t eff_in, unsigned long P)
 {
 	int i;
@@ -419,19 +419,19 @@ static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr,
 			prot = pmd_flags(*start);
 			eff = effective_prot(eff_in, prot);
 			if (pmd_large(*start) || !pmd_present(*start)) {
-				note_page(m, st, __pgprot(prot), eff, 4);
-			} else if (!kasan_page_table(m, st, pmd_start)) {
-				walk_pte_level(m, st, *start, eff,
+				note_page(st, __pgprot(prot), eff, 4);
+			} else if (!kasan_page_table(st, pmd_start)) {
+				walk_pte_level(st, *start, eff,
 					       P + i * PMD_LEVEL_MULT);
 			}
 		} else
-			note_page(m, st, __pgprot(0), 0, 4);
+			note_page(st, __pgprot(0), 0, 4);
 		start++;
 	}
 }
 
 #else
-#define walk_pmd_level(m,s,a,e,p) walk_pte_level(m,s,__pmd(pud_val(a)),e,p)
+#define walk_pmd_level(s,a,e,p) walk_pte_level(s,__pmd(pud_val(a)),e,p)
 #undef pud_large
 #define pud_large(a) pmd_large(__pmd(pud_val(a)))
 #define pud_none(a)  pmd_none(__pmd(pud_val(a)))
@@ -439,8 +439,8 @@ static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr,
 
 #if PTRS_PER_PUD > 1
 
-static void walk_pud_level(struct seq_file *m, struct pg_state *st, p4d_t addr,
-			   pgprotval_t eff_in, unsigned long P)
+static void walk_pud_level(struct pg_state *st, p4d_t addr, pgprotval_t eff_in,
+			   unsigned long P)
 {
 	int i;
 	pud_t *start, *pud_start;
@@ -455,13 +455,13 @@ static void walk_pud_level(struct seq_file *m, struct pg_state *st, p4d_t addr,
 			prot = pud_flags(*start);
 			eff = effective_prot(eff_in, prot);
 			if (pud_large(*start) || !pud_present(*start)) {
-				note_page(m, st, __pgprot(prot), eff, 3);
-			} else if (!kasan_page_table(m, st, pud_start)) {
-				walk_pmd_level(m, st, *start, eff,
+				note_page(st, __pgprot(prot), eff, 3);
+			} else if (!kasan_page_table(st, pud_start)) {
+				walk_pmd_level(st, *start, eff,
 					       P + i * PUD_LEVEL_MULT);
 			}
 		} else
-			note_page(m, st, __pgprot(0), 0, 3);
+			note_page(st, __pgprot(0), 0, 3);
 
 		prev_pud = start;
 		start++;
@@ -469,21 +469,21 @@ static void walk_pud_level(struct seq_file *m, struct pg_state *st, p4d_t addr,
 }
 
 #else
-#define walk_pud_level(m,s,a,e,p) walk_pmd_level(m,s,__pud(p4d_val(a)),e,p)
+#define walk_pud_level(s,a,e,p) walk_pmd_level(s,__pud(p4d_val(a)),e,p)
 #undef p4d_large
 #define p4d_large(a) pud_large(__pud(p4d_val(a)))
 #define p4d_none(a)  pud_none(__pud(p4d_val(a)))
 #endif
 
-static void walk_p4d_level(struct seq_file *m, struct pg_state *st, pgd_t addr,
-			   pgprotval_t eff_in, unsigned long P)
+static void walk_p4d_level(struct pg_state *st, pgd_t addr, pgprotval_t eff_in,
+			   unsigned long P)
 {
 	int i;
 	p4d_t *start, *p4d_start;
 	pgprotval_t prot, eff;
 
 	if (PTRS_PER_P4D == 1)
-		return walk_pud_level(m, st, __p4d(pgd_val(addr)), eff_in, P);
+		return walk_pud_level(st, __p4d(pgd_val(addr)), eff_in, P);
 
 	p4d_start = start = (p4d_t *)pgd_page_vaddr(addr);
 
@@ -493,13 +493,13 @@ static void walk_p4d_level(struct seq_file *m, struct pg_state *st, pgd_t addr,
 			prot = p4d_flags(*start);
 			eff = effective_prot(eff_in, prot);
 			if (p4d_large(*start) || !p4d_present(*start)) {
-				note_page(m, st, __pgprot(prot), eff, 2);
-			} else if (!kasan_page_table(m, st, p4d_start)) {
-				walk_pud_level(m, st, *start, eff,
+				note_page(st, __pgprot(prot), eff, 2);
+			} else if (!kasan_page_table(st, p4d_start)) {
+				walk_pud_level(st, *start, eff,
 					       P + i * P4D_LEVEL_MULT);
 			}
 		} else
-			note_page(m, st, __pgprot(0), 0, 2);
+			note_page(st, __pgprot(0), 0, 2);
 
 		start++;
 	}
@@ -537,6 +537,7 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 	}
 
 	st.check_wx = checkwx;
+	st.seq = m;
 	if (checkwx)
 		st.wx_pages = 0;
 
@@ -550,13 +551,13 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 			eff = prot;
 #endif
 			if (pgd_large(*start) || !pgd_present(*start)) {
-				note_page(m, &st, __pgprot(prot), eff, 1);
+				note_page(&st, __pgprot(prot), eff, 1);
 			} else {
-				walk_p4d_level(m, &st, *start, eff,
+				walk_p4d_level(&st, *start, eff,
 					       i * PGD_LEVEL_MULT);
 			}
 		} else
-			note_page(m, &st, __pgprot(0), 0, 1);
+			note_page(&st, __pgprot(0), 0, 1);
 
 		cond_resched();
 		start++;
@@ -564,7 +565,7 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 
 	/* Flush out the last page */
 	st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
-	note_page(m, &st, __pgprot(0), 0, 0);
+	note_page(&st, __pgprot(0), 0, 0);
 	if (!checkwx)
 		return;
 	if (st.wx_pages)
-- 
2.20.1


^ permalink raw reply	[flat|nested] 31+ messages in thread

* [PATCH v2 10/13] x86/mm+efi: Convert ptdump_walk_pgd_level() to take a mm_struct
  2019-02-21 11:34 [PATCH v2 00/13] Convert x86 & arm64 to use generic page walk Steven Price
                   ` (8 preceding siblings ...)
  2019-02-21 11:34 ` [PATCH v2 09/13] x86/mm: Point to struct seq_file from struct pg_state Steven Price
@ 2019-02-21 11:34 ` Steven Price
  2019-02-21 11:35 ` [PATCH v2 11/13] x86/mm: Convert ptdump_walk_pgd_level_debugfs() to take an mm_struct Steven Price
                   ` (2 subsequent siblings)
  12 siblings, 0 replies; 31+ messages in thread
From: Steven Price @ 2019-02-21 11:34 UTC (permalink / raw)
  To: linux-mm
  Cc: Steven Price, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

To enable x86 to use the generic walk_page_range() function, the
callers of ptdump_walk_pgd_level() need to pass an mm_struct rather
than the raw pgd_t pointer. Luckily since commit 7e904a91bf60
("efi: Use efi_mm in x86 as well as ARM") we now have an mm_struct
for EFI on x86.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/x86/include/asm/pgtable.h | 2 +-
 arch/x86/mm/dump_pagetables.c  | 4 ++--
 arch/x86/platform/efi/efi_32.c | 2 +-
 arch/x86/platform/efi/efi_64.c | 4 ++--
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 3695f6acb6af..371901283d5f 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -27,7 +27,7 @@
 extern pgd_t early_top_pgt[PTRS_PER_PGD];
 int __init __early_make_pgtable(unsigned long address, pmdval_t pmd);
 
-void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd);
+void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm);
 void ptdump_walk_pgd_level_debugfs(struct seq_file *m, pgd_t *pgd, bool user);
 void ptdump_walk_pgd_level_checkwx(void);
 void ptdump_walk_user_pgd_level_checkwx(void);
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index b1b86157d456..07f62d5517da 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -575,9 +575,9 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 		pr_info("x86/mm: Checked W+X mappings: passed, no W+X pages found.\n");
 }
 
-void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd)
+void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm)
 {
-	ptdump_walk_pgd_level_core(m, pgd, false, true);
+	ptdump_walk_pgd_level_core(m, mm->pgd, false, true);
 }
 
 void ptdump_walk_pgd_level_debugfs(struct seq_file *m, pgd_t *pgd, bool user)
diff --git a/arch/x86/platform/efi/efi_32.c b/arch/x86/platform/efi/efi_32.c
index 9959657127f4..9175ceaa6e72 100644
--- a/arch/x86/platform/efi/efi_32.c
+++ b/arch/x86/platform/efi/efi_32.c
@@ -49,7 +49,7 @@ void efi_sync_low_kernel_mappings(void) {}
 void __init efi_dump_pagetable(void)
 {
 #ifdef CONFIG_EFI_PGT_DUMP
-	ptdump_walk_pgd_level(NULL, swapper_pg_dir);
+	ptdump_walk_pgd_level(NULL, init_mm);
 #endif
 }
 
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index cf0347f61b21..a2e0f9800190 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -611,9 +611,9 @@ void __init efi_dump_pagetable(void)
 {
 #ifdef CONFIG_EFI_PGT_DUMP
 	if (efi_enabled(EFI_OLD_MEMMAP))
-		ptdump_walk_pgd_level(NULL, swapper_pg_dir);
+		ptdump_walk_pgd_level(NULL, init_mm);
 	else
-		ptdump_walk_pgd_level(NULL, efi_mm.pgd);
+		ptdump_walk_pgd_level(NULL, efi_mm);
 #endif
 }
 
-- 
2.20.1


^ permalink raw reply	[flat|nested] 31+ messages in thread

* [PATCH v2 11/13] x86/mm: Convert ptdump_walk_pgd_level_debugfs() to take an mm_struct
  2019-02-21 11:34 [PATCH v2 00/13] Convert x86 & arm64 to use generic page walk Steven Price
                   ` (9 preceding siblings ...)
  2019-02-21 11:34 ` [PATCH v2 10/13] x86/mm+efi: Convert ptdump_walk_pgd_level() to take a mm_struct Steven Price
@ 2019-02-21 11:35 ` Steven Price
  2019-02-21 11:35 ` [PATCH v2 12/13] x86/mm: Convert ptdump_walk_pgd_level_core() " Steven Price
  2019-02-21 11:35 ` [PATCH v2 13/13] x86: mm: Convert dump_pagetables to use walk_page_range Steven Price
  12 siblings, 0 replies; 31+ messages in thread
From: Steven Price @ 2019-02-21 11:35 UTC (permalink / raw)
  To: linux-mm
  Cc: Steven Price, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

To enable x86 to use the generic walk_page_range() function, the
callers of ptdump_walk_pgd_level_debugfs() need to pass in the mm_struct.

This means that ptdump_walk_pgd_level_core() is now always passed a
valid pgd, so drop the support for pgd==NULL.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/x86/include/asm/pgtable.h |  3 ++-
 arch/x86/mm/debug_pagetables.c |  8 ++++----
 arch/x86/mm/dump_pagetables.c  | 14 ++++++--------
 3 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 371901283d5f..ab2aa3eb05e9 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -28,7 +28,8 @@ extern pgd_t early_top_pgt[PTRS_PER_PGD];
 int __init __early_make_pgtable(unsigned long address, pmdval_t pmd);
 
 void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm);
-void ptdump_walk_pgd_level_debugfs(struct seq_file *m, pgd_t *pgd, bool user);
+void ptdump_walk_pgd_level_debugfs(struct seq_file *m, struct mm_struct *mm,
+				   bool user);
 void ptdump_walk_pgd_level_checkwx(void);
 void ptdump_walk_user_pgd_level_checkwx(void);
 
diff --git a/arch/x86/mm/debug_pagetables.c b/arch/x86/mm/debug_pagetables.c
index cd84f067e41d..824131052574 100644
--- a/arch/x86/mm/debug_pagetables.c
+++ b/arch/x86/mm/debug_pagetables.c
@@ -6,7 +6,7 @@
 
 static int ptdump_show(struct seq_file *m, void *v)
 {
-	ptdump_walk_pgd_level_debugfs(m, NULL, false);
+	ptdump_walk_pgd_level_debugfs(m, &init_mm, false);
 	return 0;
 }
 
@@ -16,7 +16,7 @@ static int ptdump_curknl_show(struct seq_file *m, void *v)
 {
 	if (current->mm->pgd) {
 		down_read(&current->mm->mmap_sem);
-		ptdump_walk_pgd_level_debugfs(m, current->mm->pgd, false);
+		ptdump_walk_pgd_level_debugfs(m, current->mm, false);
 		up_read(&current->mm->mmap_sem);
 	}
 	return 0;
@@ -31,7 +31,7 @@ static int ptdump_curusr_show(struct seq_file *m, void *v)
 {
 	if (current->mm->pgd) {
 		down_read(&current->mm->mmap_sem);
-		ptdump_walk_pgd_level_debugfs(m, current->mm->pgd, true);
+		ptdump_walk_pgd_level_debugfs(m, current->mm, true);
 		up_read(&current->mm->mmap_sem);
 	}
 	return 0;
@@ -46,7 +46,7 @@ static struct dentry *pe_efi;
 static int ptdump_efi_show(struct seq_file *m, void *v)
 {
 	if (efi_mm.pgd)
-		ptdump_walk_pgd_level_debugfs(m, efi_mm.pgd, false);
+		ptdump_walk_pgd_level_debugfs(m, &efi_mm, false);
 	return 0;
 }
 
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 07f62d5517da..8b457a65ad8e 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -526,16 +526,12 @@ static inline bool is_hypervisor_range(int idx)
 static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 				       bool checkwx, bool dmesg)
 {
-	pgd_t *start = INIT_PGD;
+	pgd_t *start = pgd;
 	pgprotval_t prot, eff;
 	int i;
 	struct pg_state st = {};
 
-	if (pgd) {
-		start = pgd;
-		st.to_dmesg = dmesg;
-	}
-
+	st.to_dmesg = dmesg;
 	st.check_wx = checkwx;
 	st.seq = m;
 	if (checkwx)
@@ -580,8 +576,10 @@ void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm)
 	ptdump_walk_pgd_level_core(m, mm->pgd, false, true);
 }
 
-void ptdump_walk_pgd_level_debugfs(struct seq_file *m, pgd_t *pgd, bool user)
+void ptdump_walk_pgd_level_debugfs(struct seq_file *m, struct mm_struct *mm,
+				   bool user)
 {
+	pgd_t *pgd = mm->pgd;
 #ifdef CONFIG_PAGE_TABLE_ISOLATION
 	if (user && static_cpu_has(X86_FEATURE_PTI))
 		pgd = kernel_to_user_pgdp(pgd);
@@ -607,7 +605,7 @@ void ptdump_walk_user_pgd_level_checkwx(void)
 
 void ptdump_walk_pgd_level_checkwx(void)
 {
-	ptdump_walk_pgd_level_core(NULL, NULL, true, false);
+	ptdump_walk_pgd_level_core(NULL, INIT_PGD, true, false);
 }
 
 static int __init pt_dump_init(void)
-- 
2.20.1


^ permalink raw reply	[flat|nested] 31+ messages in thread

* [PATCH v2 12/13] x86/mm: Convert ptdump_walk_pgd_level_core() to take an mm_struct
  2019-02-21 11:34 [PATCH v2 00/13] Convert x86 & arm64 to use generic page walk Steven Price
                   ` (10 preceding siblings ...)
  2019-02-21 11:35 ` [PATCH v2 11/13] x86/mm: Convert ptdump_walk_pgd_level_debugfs() to take an mm_struct Steven Price
@ 2019-02-21 11:35 ` Steven Price
  2019-02-21 11:35 ` [PATCH v2 13/13] x86: mm: Convert dump_pagetables to use walk_page_range Steven Price
  12 siblings, 0 replies; 31+ messages in thread
From: Steven Price @ 2019-02-21 11:35 UTC (permalink / raw)
  To: linux-mm
  Cc: Steven Price, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

An mm_struct is needed to enable x86 to use of the generic
walk_page_range() function.

In the case of walking the user page tables (when
CONFIG_PAGE_TABLE_ISOLATION is enabled), it is necessary to create a
fake_mm structure because there isn't an mm_struct with a pointer
to the pgd of the user page tables. This fake_mm structure is
initialised with the minimum necessary for the generic page walk code.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/x86/mm/dump_pagetables.c | 36 ++++++++++++++++++++---------------
 1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 8b457a65ad8e..0953bf44d792 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -111,8 +111,6 @@ static struct addr_marker address_markers[] = {
 	[END_OF_SPACE_NR]	= { -1,			NULL }
 };
 
-#define INIT_PGD	((pgd_t *) &init_top_pgt)
-
 #else /* CONFIG_X86_64 */
 
 enum address_markers_idx {
@@ -147,8 +145,6 @@ static struct addr_marker address_markers[] = {
 	[END_OF_SPACE_NR]	= { -1,			NULL }
 };
 
-#define INIT_PGD	(swapper_pg_dir)
-
 #endif /* !CONFIG_X86_64 */
 
 /* Multipliers for offsets within the PTEs */
@@ -523,10 +519,10 @@ static inline bool is_hypervisor_range(int idx)
 #endif
 }
 
-static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
+static void ptdump_walk_pgd_level_core(struct seq_file *m, struct mm_struct *mm,
 				       bool checkwx, bool dmesg)
 {
-	pgd_t *start = pgd;
+	pgd_t *start = mm->pgd;
 	pgprotval_t prot, eff;
 	int i;
 	struct pg_state st = {};
@@ -573,39 +569,49 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 
 void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm)
 {
-	ptdump_walk_pgd_level_core(m, mm->pgd, false, true);
+	ptdump_walk_pgd_level_core(m, mm, false, true);
 }
 
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+static void ptdump_walk_pgd_level_user_core(struct seq_file *m,
+					    struct mm_struct *mm,
+					    bool checkwx, bool dmesg)
+{
+	struct mm_struct fake_mm = {
+		.pgd = kernel_to_user_pgdp(mm->pgd)
+	};
+	init_rwsem(&fake_mm.mmap_sem);
+	ptdump_walk_pgd_level_core(m, &fake_mm, checkwx, dmesg);
+}
+#endif
+
 void ptdump_walk_pgd_level_debugfs(struct seq_file *m, struct mm_struct *mm,
 				   bool user)
 {
-	pgd_t *pgd = mm->pgd;
 #ifdef CONFIG_PAGE_TABLE_ISOLATION
 	if (user && static_cpu_has(X86_FEATURE_PTI))
-		pgd = kernel_to_user_pgdp(pgd);
+		ptdump_walk_pgd_level_user_core(m, mm, false, false);
+	else
 #endif
-	ptdump_walk_pgd_level_core(m, pgd, false, false);
+		ptdump_walk_pgd_level_core(m, mm, false, false);
 }
 EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level_debugfs);
 
 void ptdump_walk_user_pgd_level_checkwx(void)
 {
 #ifdef CONFIG_PAGE_TABLE_ISOLATION
-	pgd_t *pgd = INIT_PGD;
-
 	if (!(__supported_pte_mask & _PAGE_NX) ||
 	    !static_cpu_has(X86_FEATURE_PTI))
 		return;
 
 	pr_info("x86/mm: Checking user space page tables\n");
-	pgd = kernel_to_user_pgdp(pgd);
-	ptdump_walk_pgd_level_core(NULL, pgd, true, false);
+	ptdump_walk_pgd_level_user_core(NULL, &init_mm, true, false);
 #endif
 }
 
 void ptdump_walk_pgd_level_checkwx(void)
 {
-	ptdump_walk_pgd_level_core(NULL, INIT_PGD, true, false);
+	ptdump_walk_pgd_level_core(NULL, &init_mm, true, false);
 }
 
 static int __init pt_dump_init(void)
-- 
2.20.1


^ permalink raw reply	[flat|nested] 31+ messages in thread

* [PATCH v2 13/13] x86: mm: Convert dump_pagetables to use walk_page_range
  2019-02-21 11:34 [PATCH v2 00/13] Convert x86 & arm64 to use generic page walk Steven Price
                   ` (11 preceding siblings ...)
  2019-02-21 11:35 ` [PATCH v2 12/13] x86/mm: Convert ptdump_walk_pgd_level_core() " Steven Price
@ 2019-02-21 11:35 ` Steven Price
  12 siblings, 0 replies; 31+ messages in thread
From: Steven Price @ 2019-02-21 11:35 UTC (permalink / raw)
  To: linux-mm
  Cc: Steven Price, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

Make use of the new functionality in walk_page_range to remove the
arch page walking code and use the generic code to walk the page tables.

The effective permissions are passed down the chain using new fields
in struct pg_state.

The KASAN optimisation is implemented by including test_p?d callbacks
which can decide to skip an entire tree of entries

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/x86/mm/dump_pagetables.c | 282 ++++++++++++++++++----------------
 1 file changed, 146 insertions(+), 136 deletions(-)

diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 0953bf44d792..64d1619493a4 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -33,6 +33,10 @@ struct pg_state {
 	int level;
 	pgprot_t current_prot;
 	pgprotval_t effective_prot;
+	pgprotval_t effective_prot_pgd;
+	pgprotval_t effective_prot_p4d;
+	pgprotval_t effective_prot_pud;
+	pgprotval_t effective_prot_pmd;
 	unsigned long start_address;
 	unsigned long current_address;
 	const struct addr_marker *marker;
@@ -355,22 +359,21 @@ static inline pgprotval_t effective_prot(pgprotval_t prot1, pgprotval_t prot2)
 	       ((prot1 | prot2) & _PAGE_NX);
 }
 
-static void walk_pte_level(struct pg_state *st, pmd_t addr, pgprotval_t eff_in,
-			   unsigned long P)
+static int ptdump_pte_entry(pte_t *pte, unsigned long addr,
+			    unsigned long next, struct mm_walk *walk)
 {
-	int i;
-	pte_t *pte;
-	pgprotval_t prot, eff;
-
-	for (i = 0; i < PTRS_PER_PTE; i++) {
-		st->current_address = normalize_addr(P + i * PTE_LEVEL_MULT);
-		pte = pte_offset_map(&addr, st->current_address);
-		prot = pte_flags(*pte);
-		eff = effective_prot(eff_in, prot);
-		note_page(st, __pgprot(prot), eff, 5);
-		pte_unmap(pte);
-	}
+	struct pg_state *st = walk->private;
+	pgprotval_t eff, prot;
+
+	st->current_address = normalize_addr(addr);
+
+	prot = pte_flags(*pte);
+	eff = effective_prot(st->effective_prot_pmd, prot);
+	note_page(st, __pgprot(prot), eff, 5);
+
+	return 0;
 }
+
 #ifdef CONFIG_KASAN
 
 /*
@@ -399,133 +402,152 @@ static inline bool kasan_page_table(struct pg_state *st, void *pt)
 }
 #endif
 
-#if PTRS_PER_PMD > 1
-
-static void walk_pmd_level(struct pg_state *st, pud_t addr,
-			   pgprotval_t eff_in, unsigned long P)
+static int ptdump_test_pmd(unsigned long addr, unsigned long next,
+			   pmd_t *pmd, struct mm_walk *walk)
 {
-	int i;
-	pmd_t *start, *pmd_start;
-	pgprotval_t prot, eff;
-
-	pmd_start = start = (pmd_t *)pud_page_vaddr(addr);
-	for (i = 0; i < PTRS_PER_PMD; i++) {
-		st->current_address = normalize_addr(P + i * PMD_LEVEL_MULT);
-		if (!pmd_none(*start)) {
-			prot = pmd_flags(*start);
-			eff = effective_prot(eff_in, prot);
-			if (pmd_large(*start) || !pmd_present(*start)) {
-				note_page(st, __pgprot(prot), eff, 4);
-			} else if (!kasan_page_table(st, pmd_start)) {
-				walk_pte_level(st, *start, eff,
-					       P + i * PMD_LEVEL_MULT);
-			}
-		} else
-			note_page(st, __pgprot(0), 0, 4);
-		start++;
-	}
+	struct pg_state *st = walk->private;
+
+	st->current_address = normalize_addr(addr);
+
+	if (kasan_page_table(st, pmd))
+		return 1;
+	return 0;
 }
 
-#else
-#define walk_pmd_level(s,a,e,p) walk_pte_level(s,__pmd(pud_val(a)),e,p)
-#undef pud_large
-#define pud_large(a) pmd_large(__pmd(pud_val(a)))
-#define pud_none(a)  pmd_none(__pmd(pud_val(a)))
-#endif
+static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr,
+			    unsigned long next, struct mm_walk *walk)
+{
+	struct pg_state *st = walk->private;
+	pgprotval_t eff, prot;
+
+	prot = pmd_flags(*pmd);
+	eff = effective_prot(st->effective_prot_pud, prot);
+
+	st->current_address = normalize_addr(addr);
+
+	if (pmd_large(*pmd))
+		note_page(st, __pgprot(prot), eff, 4);
 
-#if PTRS_PER_PUD > 1
+	st->effective_prot_pmd = eff;
 
-static void walk_pud_level(struct pg_state *st, p4d_t addr, pgprotval_t eff_in,
-			   unsigned long P)
+	return 0;
+}
+
+static int ptdump_test_pud(unsigned long addr, unsigned long next,
+			   pud_t *pud, struct mm_walk *walk)
 {
-	int i;
-	pud_t *start, *pud_start;
-	pgprotval_t prot, eff;
-	pud_t *prev_pud = NULL;
-
-	pud_start = start = (pud_t *)p4d_page_vaddr(addr);
-
-	for (i = 0; i < PTRS_PER_PUD; i++) {
-		st->current_address = normalize_addr(P + i * PUD_LEVEL_MULT);
-		if (!pud_none(*start)) {
-			prot = pud_flags(*start);
-			eff = effective_prot(eff_in, prot);
-			if (pud_large(*start) || !pud_present(*start)) {
-				note_page(st, __pgprot(prot), eff, 3);
-			} else if (!kasan_page_table(st, pud_start)) {
-				walk_pmd_level(st, *start, eff,
-					       P + i * PUD_LEVEL_MULT);
-			}
-		} else
-			note_page(st, __pgprot(0), 0, 3);
+	struct pg_state *st = walk->private;
 
-		prev_pud = start;
-		start++;
-	}
+	st->current_address = normalize_addr(addr);
+
+	if (kasan_page_table(st, pud))
+		return 1;
+	return 0;
 }
 
-#else
-#define walk_pud_level(s,a,e,p) walk_pmd_level(s,__pud(p4d_val(a)),e,p)
-#undef p4d_large
-#define p4d_large(a) pud_large(__pud(p4d_val(a)))
-#define p4d_none(a)  pud_none(__pud(p4d_val(a)))
-#endif
+static int ptdump_pud_entry(pud_t *pud, unsigned long addr,
+			    unsigned long next, struct mm_walk *walk)
+{
+	struct pg_state *st = walk->private;
+	pgprotval_t eff, prot;
+
+	prot = pud_flags(*pud);
+	eff = effective_prot(st->effective_prot_p4d, prot);
+
+	st->current_address = normalize_addr(addr);
+
+	if (pud_large(*pud))
+		note_page(st, __pgprot(prot), eff, 3);
+
+	st->effective_prot_pud = eff;
 
-static void walk_p4d_level(struct pg_state *st, pgd_t addr, pgprotval_t eff_in,
-			   unsigned long P)
+	return 0;
+}
+
+static int ptdump_test_p4d(unsigned long addr, unsigned long next,
+			   p4d_t *p4d, struct mm_walk *walk)
 {
-	int i;
-	p4d_t *start, *p4d_start;
-	pgprotval_t prot, eff;
-
-	if (PTRS_PER_P4D == 1)
-		return walk_pud_level(st, __p4d(pgd_val(addr)), eff_in, P);
-
-	p4d_start = start = (p4d_t *)pgd_page_vaddr(addr);
-
-	for (i = 0; i < PTRS_PER_P4D; i++) {
-		st->current_address = normalize_addr(P + i * P4D_LEVEL_MULT);
-		if (!p4d_none(*start)) {
-			prot = p4d_flags(*start);
-			eff = effective_prot(eff_in, prot);
-			if (p4d_large(*start) || !p4d_present(*start)) {
-				note_page(st, __pgprot(prot), eff, 2);
-			} else if (!kasan_page_table(st, p4d_start)) {
-				walk_pud_level(st, *start, eff,
-					       P + i * P4D_LEVEL_MULT);
-			}
-		} else
-			note_page(st, __pgprot(0), 0, 2);
+	struct pg_state *st = walk->private;
 
-		start++;
-	}
+	st->current_address = normalize_addr(addr);
+
+	if (kasan_page_table(st, p4d))
+		return 1;
+	return 0;
 }
 
-#undef pgd_large
-#define pgd_large(a) (pgtable_l5_enabled() ? pgd_large(a) : p4d_large(__p4d(pgd_val(a))))
-#define pgd_none(a)  (pgtable_l5_enabled() ? pgd_none(a) : p4d_none(__p4d(pgd_val(a))))
+static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr,
+			    unsigned long next, struct mm_walk *walk)
+{
+	struct pg_state *st = walk->private;
+	pgprotval_t eff, prot;
+
+	prot = p4d_flags(*p4d);
+	eff = effective_prot(st->effective_prot_pgd, prot);
+
+	st->current_address = normalize_addr(addr);
+
+	if (p4d_large(*p4d))
+		note_page(st, __pgprot(prot), eff, 2);
+
+	st->effective_prot_p4d = eff;
+
+	return 0;
+}
 
-static inline bool is_hypervisor_range(int idx)
+static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr,
+			    unsigned long next, struct mm_walk *walk)
 {
-#ifdef CONFIG_X86_64
-	/*
-	 * A hole in the beginning of kernel address space reserved
-	 * for a hypervisor.
-	 */
-	return	(idx >= pgd_index(GUARD_HOLE_BASE_ADDR)) &&
-		(idx <  pgd_index(GUARD_HOLE_END_ADDR));
+	struct pg_state *st = walk->private;
+	pgprotval_t eff, prot;
+
+	prot = pgd_flags(*pgd);
+
+#ifdef CONFIG_X86_PAE
+	eff = _PAGE_USER | _PAGE_RW;
 #else
-	return false;
+	eff = prot;
 #endif
+
+	st->current_address = normalize_addr(addr);
+
+	if (pgd_large(*pgd))
+		note_page(st, __pgprot(prot), eff, 1);
+
+	st->effective_prot_pgd = eff;
+
+	return 0;
+}
+
+static int ptdump_hole(unsigned long addr, unsigned long next, int depth,
+		       struct mm_walk *walk)
+{
+	struct pg_state *st = walk->private;
+
+	st->current_address = normalize_addr(addr);
+
+	note_page(st, __pgprot(0), 0, depth + 1);
+
+	return 0;
 }
 
 static void ptdump_walk_pgd_level_core(struct seq_file *m, struct mm_struct *mm,
 				       bool checkwx, bool dmesg)
 {
-	pgd_t *start = mm->pgd;
-	pgprotval_t prot, eff;
-	int i;
 	struct pg_state st = {};
+	struct mm_walk walk = {
+		.mm		= mm,
+		.pgd_entry	= ptdump_pgd_entry,
+		.p4d_entry	= ptdump_p4d_entry,
+		.pud_entry	= ptdump_pud_entry,
+		.pmd_entry	= ptdump_pmd_entry,
+		.pte_entry	= ptdump_pte_entry,
+		.test_p4d	= ptdump_test_p4d,
+		.test_pud	= ptdump_test_pud,
+		.test_pmd	= ptdump_test_pmd,
+		.pte_hole	= ptdump_hole,
+		.private	= &st
+	};
 
 	st.to_dmesg = dmesg;
 	st.check_wx = checkwx;
@@ -533,27 +555,15 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, struct mm_struct *mm,
 	if (checkwx)
 		st.wx_pages = 0;
 
-	for (i = 0; i < PTRS_PER_PGD; i++) {
-		st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
-		if (!pgd_none(*start) && !is_hypervisor_range(i)) {
-			prot = pgd_flags(*start);
-#ifdef CONFIG_X86_PAE
-			eff = _PAGE_USER | _PAGE_RW;
+	down_read(&mm->mmap_sem);
+#ifdef CONFIG_X86_64
+	walk_page_range(0, PTRS_PER_PGD*PGD_LEVEL_MULT/2, &walk);
+	walk_page_range(normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT/2), ~0,
+			&walk);
 #else
-			eff = prot;
+	walk_page_range(0, ~0, &walk);
 #endif
-			if (pgd_large(*start) || !pgd_present(*start)) {
-				note_page(&st, __pgprot(prot), eff, 1);
-			} else {
-				walk_p4d_level(&st, *start, eff,
-					       i * PGD_LEVEL_MULT);
-			}
-		} else
-			note_page(&st, __pgprot(0), 0, 1);
-
-		cond_resched();
-		start++;
-	}
+	up_read(&mm->mmap_sem);
 
 	/* Flush out the last page */
 	st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
-- 
2.20.1


^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-02-21 11:34 ` [PATCH v2 03/13] mm: Add generic p?d_large() macros Steven Price
@ 2019-02-21 13:41   ` Mark Rutland
  2019-02-21 14:28   ` Kirill A. Shutemov
  1 sibling, 0 replies; 31+ messages in thread
From: Mark Rutland @ 2019-02-21 13:41 UTC (permalink / raw)
  To: Steven Price
  Cc: linux-mm, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Liang, Kan

On Thu, Feb 21, 2019 at 11:34:52AM +0000, Steven Price wrote:
> From: James Morse <james.morse@arm.com>
> 
> Exposing the pud/pgd levels of the page tables to walk_page_range() means
> we may come across the exotic large mappings that come with large areas
> of contiguous memory (such as the kernel's linear map).
> 
> For architectures that don't provide p?d_large() macros, provided a
> does nothing default.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  include/asm-generic/pgtable.h | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
> index 05e61e6c843f..f0de24100ac6 100644
> --- a/include/asm-generic/pgtable.h
> +++ b/include/asm-generic/pgtable.h
> @@ -1186,4 +1186,23 @@ static inline bool arch_has_pfn_modify_check(void)
>  #define mm_pmd_folded(mm)	__is_defined(__PAGETABLE_PMD_FOLDED)
>  #endif
>  
> +/*
> + * p?d_large() - true if this entry is a final mapping to a physical address.

It might make sense to s/final/leaf/, but otherwise that's a great
definition!

> + * This differs from p?d_huge() by the fact that they are always available (if
> + * the architecture supports large pages at the appropriate level) even
> + * if CONFIG_HUGETLB_PAGE is not defined.

I'm not sure if we need this part, since we don't mention
p?d_trans_huge(), etc, but either way:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Thanks,
Mark.

> + */
> +#ifndef pgd_large
> +#define pgd_large(x)	0
> +#endif
> +#ifndef p4d_large
> +#define p4d_large(x)	0
> +#endif
> +#ifndef pud_large
> +#define pud_large(x)	0
> +#endif
> +#ifndef pmd_large
> +#define pmd_large(x)	0
> +#endif
> +
>  #endif /* _ASM_GENERIC_PGTABLE_H */
> -- 
> 2.20.1
> 

^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 01/13] arm64: mm: Add p?d_large() definitions
  2019-02-21 11:34 ` [PATCH v2 01/13] arm64: mm: Add p?d_large() definitions Steven Price
@ 2019-02-21 13:52   ` Mark Rutland
  0 siblings, 0 replies; 31+ messages in thread
From: Mark Rutland @ 2019-02-21 13:52 UTC (permalink / raw)
  To: Steven Price
  Cc: linux-mm, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Liang, Kan

On Thu, Feb 21, 2019 at 11:34:50AM +0000, Steven Price wrote:
> From: James Morse <james.morse@arm.com>
> 
> Exposing the pud/pgd levels of the page tables to walk_page_range() means
> we may come across the exotic large mappings that come with large areas
> of contiguous memory (such as the kernel's linear map).
> 
> Expose p?d_large() from each architecture to detect these large mappings.
> 
> arm64 already has these macros defined, but with a different name.
> p?d_large() is used by s390, sparc and x86. Only arm/arm64 use p?d_sect().
> Add a macro to allow both names.

So that we can avoid conflciting terminology, could we reword this as:

A generic walk_page_range() needs to handle exotic leaf entries at
arbitrary depths in the page tables (e.g. section mappings in the
kernel's linear map, or huge pages in userspace page tables).

Currently there is no generic API to detect such entries, but s390,
sparc, and x86 have all aligned on p?d_large(). Let's implement the same
for arm64 atop of p?d_cont().

With that:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Thanks,
Mark.

> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm64/include/asm/pgtable.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index de70c1eabf33..09d308921625 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -428,6 +428,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
>  				 PMD_TYPE_TABLE)
>  #define pmd_sect(pmd)		((pmd_val(pmd) & PMD_TYPE_MASK) == \
>  				 PMD_TYPE_SECT)
> +#define pmd_large(x)		pmd_sect(x)
>  
>  #if defined(CONFIG_ARM64_64K_PAGES) || CONFIG_PGTABLE_LEVELS < 3
>  #define pud_sect(pud)		(0)
> @@ -435,6 +436,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
>  #else
>  #define pud_sect(pud)		((pud_val(pud) & PUD_TYPE_MASK) == \
>  				 PUD_TYPE_SECT)
> +#define pud_large(x)		pud_sect(x)
>  #define pud_table(pud)		((pud_val(pud) & PUD_TYPE_MASK) == \
>  				 PUD_TYPE_TABLE)
>  #endif
> -- 
> 2.20.1
> 

^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 02/13] x86/mm: Add p?d_large() definitions
  2019-02-21 11:34 ` [PATCH v2 02/13] x86/mm: " Steven Price
@ 2019-02-21 14:21   ` Kirill A. Shutemov
  0 siblings, 0 replies; 31+ messages in thread
From: Kirill A. Shutemov @ 2019-02-21 14:21 UTC (permalink / raw)
  To: Steven Price
  Cc: linux-mm, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

On Thu, Feb 21, 2019 at 11:34:51AM +0000, Steven Price wrote:
> Exposing the pud/pgd levels of the page tables to walk_page_range() means
> we may come across the exotic large mappings that come with large areas
> of contiguous memory (such as the kernel's linear map).
> 
> Expose p?d_large() from each architecture to detect these large mappings.
> 
> x86 already has these defined as inline functions, add a macro of the
> same name so we don't end up with the generic version too.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/x86/include/asm/pgtable.h | 3 +++
>  arch/x86/mm/dump_pagetables.c  | 3 +++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
> index 2779ace16d23..3695f6acb6af 100644
> --- a/arch/x86/include/asm/pgtable.h
> +++ b/arch/x86/include/asm/pgtable.h
> @@ -234,6 +234,7 @@ static inline int pmd_large(pmd_t pte)
>  {
>  	return pmd_flags(pte) & _PAGE_PSE;
>  }
> +#define pmd_large(x)	pmd_large(x)
>  
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  static inline int pmd_trans_huge(pmd_t pmd)
> @@ -873,6 +874,7 @@ static inline int pud_large(pud_t pud)
>  	return 0;
>  }
>  #endif	/* CONFIG_PGTABLE_LEVELS > 2 */
> +#define pud_large(x)	pud_large(x)

Nit: we usually do this in form of

#define pud_large pud_large

and before body of the inline function.

-- 
 Kirill A. Shutemov

^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-02-21 11:34 ` [PATCH v2 03/13] mm: Add generic p?d_large() macros Steven Price
  2019-02-21 13:41   ` Mark Rutland
@ 2019-02-21 14:28   ` Kirill A. Shutemov
  2019-02-21 14:46     ` Steven Price
  1 sibling, 1 reply; 31+ messages in thread
From: Kirill A. Shutemov @ 2019-02-21 14:28 UTC (permalink / raw)
  To: Steven Price
  Cc: linux-mm, Andy Lutomirski, Ard Biesheuvel, Arnd Bergmann,
	Borislav Petkov, Catalin Marinas, Dave Hansen, Ingo Molnar,
	James Morse, Jérôme Glisse, Peter Zijlstra,
	Thomas Gleixner, Will Deacon, x86, H. Peter Anvin,
	linux-arm-kernel, linux-kernel, Mark Rutland, Liang, Kan

On Thu, Feb 21, 2019 at 11:34:52AM +0000, Steven Price wrote:
> From: James Morse <james.morse@arm.com>
> 
> Exposing the pud/pgd levels of the page tables to walk_page_range() means
> we may come across the exotic large mappings that come with large areas
> of contiguous memory (such as the kernel's linear map).
> 
> For architectures that don't provide p?d_large() macros, provided a
> does nothing default.

Nak, sorry.

Power will get broken by the patch. It has pmd_large() inline function,
that will be overwritten by the define from this patch.

I believe it requires more ground work on arch side in general.
All architectures that has huge page support has to provide these helpers
(and matching defines) before you can use it in a generic code.

-- 
 Kirill A. Shutemov

^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-02-21 14:28   ` Kirill A. Shutemov
@ 2019-02-21 14:46     ` Steven Price
  2019-02-21 14:57       ` Kirill A. Shutemov
  0 siblings, 1 reply; 31+ messages in thread
From: Steven Price @ 2019-02-21 14:46 UTC (permalink / raw)
  To: Kirill A. Shutemov
  Cc: Mark Rutland, x86, Arnd Bergmann, Ard Biesheuvel, Peter Zijlstra,
	Catalin Marinas, Dave Hansen, Will Deacon, linux-kernel,
	linux-mm, Jérôme Glisse, Ingo Molnar, Borislav Petkov,
	Andy Lutomirski, H. Peter Anvin, James Morse, Thomas Gleixner,
	linux-arm-kernel, Liang, Kan

On 21/02/2019 14:28, Kirill A. Shutemov wrote:
> On Thu, Feb 21, 2019 at 11:34:52AM +0000, Steven Price wrote:
>> From: James Morse <james.morse@arm.com>
>>
>> Exposing the pud/pgd levels of the page tables to walk_page_range() means
>> we may come across the exotic large mappings that come with large areas
>> of contiguous memory (such as the kernel's linear map).
>>
>> For architectures that don't provide p?d_large() macros, provided a
>> does nothing default.
> 
> Nak, sorry.
> 
> Power will get broken by the patch. It has pmd_large() inline function,
> that will be overwritten by the define from this patch.
> 
> I believe it requires more ground work on arch side in general.
> All architectures that has huge page support has to provide these helpers
> (and matching defines) before you can use it in a generic code.

Sorry about that, I had compile tested on power, but obviously not the
right config to actually see the breakage.

I'll do some grepping - hopefully this is just a case of exposing the
functions/defines that already exist for those architectures.

Note that in terms of the new page walking code, these new defines are
only used when walking a page table without a VMA (which isn't currently
done), so architectures which don't use p?d_large currently will work
fine with the generic versions. They only need to provide meaningful
definitions when switching to use the walk-without-a-VMA functionality.

Thanks for reporting the breakage.

Steve

^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-02-21 14:46     ` Steven Price
@ 2019-02-21 14:57       ` Kirill A. Shutemov
  2019-02-21 17:16         ` Steven Price
  2019-03-01 11:49         ` Mike Rapoport
  0 siblings, 2 replies; 31+ messages in thread
From: Kirill A. Shutemov @ 2019-02-21 14:57 UTC (permalink / raw)
  To: Steven Price
  Cc: Mark Rutland, x86, Arnd Bergmann, Ard Biesheuvel, Peter Zijlstra,
	Catalin Marinas, Dave Hansen, Will Deacon, linux-kernel,
	linux-mm, Jérôme Glisse, Ingo Molnar, Borislav Petkov,
	Andy Lutomirski, H. Peter Anvin, James Morse, Thomas Gleixner,
	linux-arm-kernel, Liang, Kan

On Thu, Feb 21, 2019 at 02:46:18PM +0000, Steven Price wrote:
> On 21/02/2019 14:28, Kirill A. Shutemov wrote:
> > On Thu, Feb 21, 2019 at 11:34:52AM +0000, Steven Price wrote:
> >> From: James Morse <james.morse@arm.com>
> >>
> >> Exposing the pud/pgd levels of the page tables to walk_page_range() means
> >> we may come across the exotic large mappings that come with large areas
> >> of contiguous memory (such as the kernel's linear map).
> >>
> >> For architectures that don't provide p?d_large() macros, provided a
> >> does nothing default.
> > 
> > Nak, sorry.
> > 
> > Power will get broken by the patch. It has pmd_large() inline function,
> > that will be overwritten by the define from this patch.
> > 
> > I believe it requires more ground work on arch side in general.
> > All architectures that has huge page support has to provide these helpers
> > (and matching defines) before you can use it in a generic code.
> 
> Sorry about that, I had compile tested on power, but obviously not the
> right config to actually see the breakage.

I don't think you'll catch it at compile-time. It would silently override
the helper with always-false.

> I'll do some grepping - hopefully this is just a case of exposing the
> functions/defines that already exist for those architectures.

I see the same type of breakage on s390 and sparc.

> Note that in terms of the new page walking code, these new defines are
> only used when walking a page table without a VMA (which isn't currently
> done), so architectures which don't use p?d_large currently will work
> fine with the generic versions. They only need to provide meaningful
> definitions when switching to use the walk-without-a-VMA functionality.

How other architectures would know that they need to provide the helpers
to get walk-without-a-VMA functionality? This looks very fragile to me.

-- 
 Kirill A. Shutemov

^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-02-21 14:57       ` Kirill A. Shutemov
@ 2019-02-21 17:16         ` Steven Price
  2019-02-21 21:06           ` Kirill A. Shutemov
  2019-03-01 11:49         ` Mike Rapoport
  1 sibling, 1 reply; 31+ messages in thread
From: Steven Price @ 2019-02-21 17:16 UTC (permalink / raw)
  To: Kirill A. Shutemov
  Cc: Mark Rutland, Dave Hansen, Arnd Bergmann, Ard Biesheuvel,
	Peter Zijlstra, Catalin Marinas, x86, Will Deacon, linux-kernel,
	linux-mm, Jérôme Glisse, Ingo Molnar, Borislav Petkov,
	Andy Lutomirski, H. Peter Anvin, James Morse, Thomas Gleixner,
	linux-arm-kernel, Liang, Kan

On 21/02/2019 14:57, Kirill A. Shutemov wrote:
> On Thu, Feb 21, 2019 at 02:46:18PM +0000, Steven Price wrote:
>> On 21/02/2019 14:28, Kirill A. Shutemov wrote:
>>> On Thu, Feb 21, 2019 at 11:34:52AM +0000, Steven Price wrote:
>>>> From: James Morse <james.morse@arm.com>
>>>>
>>>> Exposing the pud/pgd levels of the page tables to walk_page_range() means
>>>> we may come across the exotic large mappings that come with large areas
>>>> of contiguous memory (such as the kernel's linear map).
>>>>
>>>> For architectures that don't provide p?d_large() macros, provided a
>>>> does nothing default.
>>>
>>> Nak, sorry.
>>>
>>> Power will get broken by the patch. It has pmd_large() inline function,
>>> that will be overwritten by the define from this patch.
>>>
>>> I believe it requires more ground work on arch side in general.
>>> All architectures that has huge page support has to provide these helpers
>>> (and matching defines) before you can use it in a generic code.
>>
>> Sorry about that, I had compile tested on power, but obviously not the
>> right config to actually see the breakage.
> 
> I don't think you'll catch it at compile-time. It would silently override
> the helper with always-false.

Ah, that might explain why I missed it.

>> I'll do some grepping - hopefully this is just a case of exposing the
>> functions/defines that already exist for those architectures.
> 
> I see the same type of breakage on s390 and sparc.
> 
>> Note that in terms of the new page walking code, these new defines are
>> only used when walking a page table without a VMA (which isn't currently
>> done), so architectures which don't use p?d_large currently will work
>> fine with the generic versions. They only need to provide meaningful
>> definitions when switching to use the walk-without-a-VMA functionality.
> 
> How other architectures would know that they need to provide the helpers
> to get walk-without-a-VMA functionality? This looks very fragile to me.

Yes, you've got a good point there. This would apply to the p?d_large
macros as well - any arch which (inadvertently) uses the generic version
is likely to be fragile/broken.

I think probably the best option here is to scrap the generic versions
altogether and simply introduce a ARCH_HAS_PXD_LARGE config option which
would enable the new functionality to those arches that opt-in. Do you
think this would be less fragile?

Thanks,

Steve

^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-02-21 17:16         ` Steven Price
@ 2019-02-21 21:06           ` Kirill A. Shutemov
  2019-02-22 10:21             ` Steven Price
  2019-03-01 11:53             ` Mike Rapoport
  0 siblings, 2 replies; 31+ messages in thread
From: Kirill A. Shutemov @ 2019-02-21 21:06 UTC (permalink / raw)
  To: Steven Price
  Cc: Mark Rutland, Dave Hansen, Arnd Bergmann, Ard Biesheuvel,
	Peter Zijlstra, Catalin Marinas, x86, Will Deacon, linux-kernel,
	linux-mm, Jérôme Glisse, Ingo Molnar, Borislav Petkov,
	Andy Lutomirski, H. Peter Anvin, James Morse, Thomas Gleixner,
	linux-arm-kernel, Liang, Kan

On Thu, Feb 21, 2019 at 05:16:46PM +0000, Steven Price wrote:
> >> Note that in terms of the new page walking code, these new defines are
> >> only used when walking a page table without a VMA (which isn't currently
> >> done), so architectures which don't use p?d_large currently will work
> >> fine with the generic versions. They only need to provide meaningful
> >> definitions when switching to use the walk-without-a-VMA functionality.
> > 
> > How other architectures would know that they need to provide the helpers
> > to get walk-without-a-VMA functionality? This looks very fragile to me.
> 
> Yes, you've got a good point there. This would apply to the p?d_large
> macros as well - any arch which (inadvertently) uses the generic version
> is likely to be fragile/broken.
> 
> I think probably the best option here is to scrap the generic versions
> altogether and simply introduce a ARCH_HAS_PXD_LARGE config option which
> would enable the new functionality to those arches that opt-in. Do you
> think this would be less fragile?

These helpers are useful beyond pagewalker.

Can we actually do some grinding and make *all* archs to provide correct
helpers? Yes, it's tedious, but not that bad.

I think we could provide generic helpers for folded levels in
<asm-generic/pgtable-nop?d.h> and rest has to be provided by the arch.
Architectures that support only 2 level paging would need to provide
pgd_large(), with 3 -- pmd_large() and so on.

-- 
 Kirill A. Shutemov

^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-02-21 21:06           ` Kirill A. Shutemov
@ 2019-02-22 10:21             ` Steven Price
  2019-03-01 11:53             ` Mike Rapoport
  1 sibling, 0 replies; 31+ messages in thread
From: Steven Price @ 2019-02-22 10:21 UTC (permalink / raw)
  To: Kirill A. Shutemov
  Cc: Mark Rutland, x86, Arnd Bergmann, Ard Biesheuvel, Peter Zijlstra,
	Catalin Marinas, Dave Hansen, Will Deacon, linux-kernel,
	linux-mm, Jérôme Glisse, Ingo Molnar, Borislav Petkov,
	Andy Lutomirski, H. Peter Anvin, James Morse, Thomas Gleixner,
	linux-arm-kernel, Liang, Kan

On 21/02/2019 21:06, Kirill A. Shutemov wrote:
> On Thu, Feb 21, 2019 at 05:16:46PM +0000, Steven Price wrote:
>>>> Note that in terms of the new page walking code, these new defines are
>>>> only used when walking a page table without a VMA (which isn't currently
>>>> done), so architectures which don't use p?d_large currently will work
>>>> fine with the generic versions. They only need to provide meaningful
>>>> definitions when switching to use the walk-without-a-VMA functionality.
>>>
>>> How other architectures would know that they need to provide the helpers
>>> to get walk-without-a-VMA functionality? This looks very fragile to me.
>>
>> Yes, you've got a good point there. This would apply to the p?d_large
>> macros as well - any arch which (inadvertently) uses the generic version
>> is likely to be fragile/broken.
>>
>> I think probably the best option here is to scrap the generic versions
>> altogether and simply introduce a ARCH_HAS_PXD_LARGE config option which
>> would enable the new functionality to those arches that opt-in. Do you
>> think this would be less fragile?
> 
> These helpers are useful beyond pagewalker.
> 
> Can we actually do some grinding and make *all* archs to provide correct
> helpers? Yes, it's tedious, but not that bad.
> 
> I think we could provide generic helpers for folded levels in
> <asm-generic/pgtable-nop?d.h> and rest has to be provided by the arch.
> Architectures that support only 2 level paging would need to provide
> pgd_large(), with 3 -- pmd_large() and so on.

Fair enough, I'll have a go and hopefully people will be able to correct
it if I make any mistakes - I'm certainly not going to be able to test
all architectures myself.

Steve

^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-02-21 14:57       ` Kirill A. Shutemov
  2019-02-21 17:16         ` Steven Price
@ 2019-03-01 11:49         ` Mike Rapoport
  2019-03-01 12:28           ` Kirill A. Shutemov
  1 sibling, 1 reply; 31+ messages in thread
From: Mike Rapoport @ 2019-03-01 11:49 UTC (permalink / raw)
  To: Kirill A. Shutemov
  Cc: Steven Price, Mark Rutland, x86, Arnd Bergmann, Ard Biesheuvel,
	Peter Zijlstra, Catalin Marinas, Dave Hansen, Will Deacon,
	linux-kernel, linux-mm, Jérôme Glisse, Ingo Molnar,
	Borislav Petkov, Andy Lutomirski, H. Peter Anvin, James Morse,
	Thomas Gleixner, linux-arm-kernel, Liang, Kan

Hi Kirill,

On Thu, Feb 21, 2019 at 05:57:06PM +0300, Kirill A. Shutemov wrote:
> On Thu, Feb 21, 2019 at 02:46:18PM +0000, Steven Price wrote:
> > On 21/02/2019 14:28, Kirill A. Shutemov wrote:
> > > On Thu, Feb 21, 2019 at 11:34:52AM +0000, Steven Price wrote:
> > >> From: James Morse <james.morse@arm.com>
> > >>
> > >> Exposing the pud/pgd levels of the page tables to walk_page_range() means
> > >> we may come across the exotic large mappings that come with large areas
> > >> of contiguous memory (such as the kernel's linear map).
> > >>
> > >> For architectures that don't provide p?d_large() macros, provided a
> > >> does nothing default.
> > > 
> > > Nak, sorry.
> > > 
> > > Power will get broken by the patch. It has pmd_large() inline function,
> > > that will be overwritten by the define from this patch.
> > > 
> > > I believe it requires more ground work on arch side in general.
> > > All architectures that has huge page support has to provide these helpers
> > > (and matching defines) before you can use it in a generic code.
> > 
> > Sorry about that, I had compile tested on power, but obviously not the
> > right config to actually see the breakage.
> 
> I don't think you'll catch it at compile-time. It would silently override
> the helper with always-false.

Can you explain why the compiler would override the helper define in, e.g.
arch/powerpc/include/asm/pgtable.h with the generic (0)?
Actually, I've tried to compile this on power with deliberately adding
errors to both power-specific and the generic definition of pmd_large and
the compilation failed the way I expected in the power-specific helper.
 
> > I'll do some grepping - hopefully this is just a case of exposing the
> > functions/defines that already exist for those architectures.
> 
> I see the same type of breakage on s390 and sparc.
> 
> > Note that in terms of the new page walking code, these new defines are
> > only used when walking a page table without a VMA (which isn't currently
> > done), so architectures which don't use p?d_large currently will work
> > fine with the generic versions. They only need to provide meaningful
> > definitions when switching to use the walk-without-a-VMA functionality.
> 
> How other architectures would know that they need to provide the helpers
> to get walk-without-a-VMA functionality? This looks very fragile to me.
> 
> -- 
>  Kirill A. Shutemov

-- 
Sincerely yours,
Mike.


^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-02-21 21:06           ` Kirill A. Shutemov
  2019-02-22 10:21             ` Steven Price
@ 2019-03-01 11:53             ` Mike Rapoport
  2019-03-01 12:30               ` Kirill A. Shutemov
  1 sibling, 1 reply; 31+ messages in thread
From: Mike Rapoport @ 2019-03-01 11:53 UTC (permalink / raw)
  To: Kirill A. Shutemov
  Cc: Steven Price, Mark Rutland, Dave Hansen, Arnd Bergmann,
	Ard Biesheuvel, Peter Zijlstra, Catalin Marinas, x86,
	Will Deacon, linux-kernel, linux-mm, Jérôme Glisse,
	Ingo Molnar, Borislav Petkov, Andy Lutomirski, H. Peter Anvin,
	James Morse, Thomas Gleixner, linux-arm-kernel, Liang, Kan

Him Kirill,

On Fri, Feb 22, 2019 at 12:06:18AM +0300, Kirill A. Shutemov wrote:
> On Thu, Feb 21, 2019 at 05:16:46PM +0000, Steven Price wrote:
> > >> Note that in terms of the new page walking code, these new defines are
> > >> only used when walking a page table without a VMA (which isn't currently
> > >> done), so architectures which don't use p?d_large currently will work
> > >> fine with the generic versions. They only need to provide meaningful
> > >> definitions when switching to use the walk-without-a-VMA functionality.
> > > 
> > > How other architectures would know that they need to provide the helpers
> > > to get walk-without-a-VMA functionality? This looks very fragile to me.
> > 
> > Yes, you've got a good point there. This would apply to the p?d_large
> > macros as well - any arch which (inadvertently) uses the generic version
> > is likely to be fragile/broken.
> > 
> > I think probably the best option here is to scrap the generic versions
> > altogether and simply introduce a ARCH_HAS_PXD_LARGE config option which
> > would enable the new functionality to those arches that opt-in. Do you
> > think this would be less fragile?
> 
> These helpers are useful beyond pagewalker.
> 
> Can we actually do some grinding and make *all* archs to provide correct
> helpers? Yes, it's tedious, but not that bad.

Many architectures simply cannot support non-leaf entries at the higher
levels. I think letting the use a generic helper actually does make sense.
 
> I think we could provide generic helpers for folded levels in
> <asm-generic/pgtable-nop?d.h> and rest has to be provided by the arch.
> Architectures that support only 2 level paging would need to provide
> pgd_large(), with 3 -- pmd_large() and so on.
> 
> -- 
>  Kirill A. Shutemov

-- 
Sincerely yours,
Mike.


^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-03-01 11:49         ` Mike Rapoport
@ 2019-03-01 12:28           ` Kirill A. Shutemov
  0 siblings, 0 replies; 31+ messages in thread
From: Kirill A. Shutemov @ 2019-03-01 12:28 UTC (permalink / raw)
  To: Mike Rapoport
  Cc: Steven Price, Mark Rutland, x86, Arnd Bergmann, Ard Biesheuvel,
	Peter Zijlstra, Catalin Marinas, Dave Hansen, Will Deacon,
	linux-kernel, linux-mm, Jérôme Glisse, Ingo Molnar,
	Borislav Petkov, Andy Lutomirski, H. Peter Anvin, James Morse,
	Thomas Gleixner, linux-arm-kernel, Liang, Kan

On Fri, Mar 01, 2019 at 01:49:53PM +0200, Mike Rapoport wrote:
> Hi Kirill,
> 
> On Thu, Feb 21, 2019 at 05:57:06PM +0300, Kirill A. Shutemov wrote:
> > On Thu, Feb 21, 2019 at 02:46:18PM +0000, Steven Price wrote:
> > > On 21/02/2019 14:28, Kirill A. Shutemov wrote:
> > > > On Thu, Feb 21, 2019 at 11:34:52AM +0000, Steven Price wrote:
> > > >> From: James Morse <james.morse@arm.com>
> > > >>
> > > >> Exposing the pud/pgd levels of the page tables to walk_page_range() means
> > > >> we may come across the exotic large mappings that come with large areas
> > > >> of contiguous memory (such as the kernel's linear map).
> > > >>
> > > >> For architectures that don't provide p?d_large() macros, provided a
> > > >> does nothing default.
> > > > 
> > > > Nak, sorry.
> > > > 
> > > > Power will get broken by the patch. It has pmd_large() inline function,
> > > > that will be overwritten by the define from this patch.
> > > > 
> > > > I believe it requires more ground work on arch side in general.
> > > > All architectures that has huge page support has to provide these helpers
> > > > (and matching defines) before you can use it in a generic code.
> > > 
> > > Sorry about that, I had compile tested on power, but obviously not the
> > > right config to actually see the breakage.
> > 
> > I don't think you'll catch it at compile-time. It would silently override
> > the helper with always-false.
> 
> Can you explain why the compiler would override the helper define in, e.g.
> arch/powerpc/include/asm/pgtable.h with the generic (0)?

This one will not be overrided, but the other one will. See

arch/powerpc/include/asm/book3s/64/pgtable.h

-- 
 Kirill A. Shutemov

^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-03-01 11:53             ` Mike Rapoport
@ 2019-03-01 12:30               ` Kirill A. Shutemov
  2019-03-01 13:39                 ` Steven Price
  0 siblings, 1 reply; 31+ messages in thread
From: Kirill A. Shutemov @ 2019-03-01 12:30 UTC (permalink / raw)
  To: Mike Rapoport
  Cc: Steven Price, Mark Rutland, Dave Hansen, Arnd Bergmann,
	Ard Biesheuvel, Peter Zijlstra, Catalin Marinas, x86,
	Will Deacon, linux-kernel, linux-mm, Jérôme Glisse,
	Ingo Molnar, Borislav Petkov, Andy Lutomirski, H. Peter Anvin,
	James Morse, Thomas Gleixner, linux-arm-kernel, Liang, Kan

On Fri, Mar 01, 2019 at 01:53:01PM +0200, Mike Rapoport wrote:
> Him Kirill,
> 
> On Fri, Feb 22, 2019 at 12:06:18AM +0300, Kirill A. Shutemov wrote:
> > On Thu, Feb 21, 2019 at 05:16:46PM +0000, Steven Price wrote:
> > > >> Note that in terms of the new page walking code, these new defines are
> > > >> only used when walking a page table without a VMA (which isn't currently
> > > >> done), so architectures which don't use p?d_large currently will work
> > > >> fine with the generic versions. They only need to provide meaningful
> > > >> definitions when switching to use the walk-without-a-VMA functionality.
> > > > 
> > > > How other architectures would know that they need to provide the helpers
> > > > to get walk-without-a-VMA functionality? This looks very fragile to me.
> > > 
> > > Yes, you've got a good point there. This would apply to the p?d_large
> > > macros as well - any arch which (inadvertently) uses the generic version
> > > is likely to be fragile/broken.
> > > 
> > > I think probably the best option here is to scrap the generic versions
> > > altogether and simply introduce a ARCH_HAS_PXD_LARGE config option which
> > > would enable the new functionality to those arches that opt-in. Do you
> > > think this would be less fragile?
> > 
> > These helpers are useful beyond pagewalker.
> > 
> > Can we actually do some grinding and make *all* archs to provide correct
> > helpers? Yes, it's tedious, but not that bad.
> 
> Many architectures simply cannot support non-leaf entries at the higher
> levels. I think letting the use a generic helper actually does make sense.

I disagree.

It's makes sense if the level doesn't exists on the arch.

But if the level exists, it will be less frugile to ask the arch to
provide the helper. Even if it is dummy always-false.

-- 
 Kirill A. Shutemov

^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-03-01 12:30               ` Kirill A. Shutemov
@ 2019-03-01 13:39                 ` Steven Price
  2019-03-03  7:12                   ` Mike Rapoport
  0 siblings, 1 reply; 31+ messages in thread
From: Steven Price @ 2019-03-01 13:39 UTC (permalink / raw)
  To: Kirill A. Shutemov, Mike Rapoport
  Cc: Mark Rutland, x86, Arnd Bergmann, Ard Biesheuvel, Peter Zijlstra,
	Catalin Marinas, Dave Hansen, Will Deacon, linux-kernel,
	linux-mm, Jérôme Glisse, Ingo Molnar, Borislav Petkov,
	Andy Lutomirski, H. Peter Anvin, James Morse, Thomas Gleixner,
	linux-arm-kernel, Liang, Kan

On 01/03/2019 12:30, Kirill A. Shutemov wrote:
> On Fri, Mar 01, 2019 at 01:53:01PM +0200, Mike Rapoport wrote:
>> Him Kirill,
>>
>> On Fri, Feb 22, 2019 at 12:06:18AM +0300, Kirill A. Shutemov wrote:
>>> On Thu, Feb 21, 2019 at 05:16:46PM +0000, Steven Price wrote:
>>>>>> Note that in terms of the new page walking code, these new defines are
>>>>>> only used when walking a page table without a VMA (which isn't currently
>>>>>> done), so architectures which don't use p?d_large currently will work
>>>>>> fine with the generic versions. They only need to provide meaningful
>>>>>> definitions when switching to use the walk-without-a-VMA functionality.
>>>>>
>>>>> How other architectures would know that they need to provide the helpers
>>>>> to get walk-without-a-VMA functionality? This looks very fragile to me.
>>>>
>>>> Yes, you've got a good point there. This would apply to the p?d_large
>>>> macros as well - any arch which (inadvertently) uses the generic version
>>>> is likely to be fragile/broken.
>>>>
>>>> I think probably the best option here is to scrap the generic versions
>>>> altogether and simply introduce a ARCH_HAS_PXD_LARGE config option which
>>>> would enable the new functionality to those arches that opt-in. Do you
>>>> think this would be less fragile?
>>>
>>> These helpers are useful beyond pagewalker.
>>>
>>> Can we actually do some grinding and make *all* archs to provide correct
>>> helpers? Yes, it's tedious, but not that bad.
>>
>> Many architectures simply cannot support non-leaf entries at the higher
>> levels. I think letting the use a generic helper actually does make sense.
> 
> I disagree.
> 
> It's makes sense if the level doesn't exists on the arch.

This is what patch 24 [1] of the series does - if the level doesn't
exist then appropriate stubs are provided.

> But if the level exists, it will be less frugile to ask the arch to
> provide the helper. Even if it is dummy always-false.

The problem (as I see it), is we need a reliable set of p?d_large()
implementations to be able to walk arbitrary page tables. Either the
entire functionality of walking page tables without a VMA has to be an
opt-in per architecture, or we need to mandate that every architecture
provide these implementations.

I could provide an asm-generic header to provide a complete set of dummy
implementations for architectures that don't support large pages at all,
but that seems a bit overkill when most architectures only need to
define 2 or 3 implementations (the rest being provided by the
folded-levels automatically).

Thanks,

Steve

[1]
https://lore.kernel.org/lkml/20190227170608.27963-25-steven.price@arm.com/

^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-03-01 13:39                 ` Steven Price
@ 2019-03-03  7:12                   ` Mike Rapoport
  2019-03-04 14:35                     ` Steven Price
  0 siblings, 1 reply; 31+ messages in thread
From: Mike Rapoport @ 2019-03-03  7:12 UTC (permalink / raw)
  To: Steven Price
  Cc: Kirill A. Shutemov, Mark Rutland, x86, Arnd Bergmann,
	Ard Biesheuvel, Peter Zijlstra, Catalin Marinas, Dave Hansen,
	Will Deacon, linux-kernel, linux-mm, Jérôme Glisse,
	Ingo Molnar, Borislav Petkov, Andy Lutomirski, H. Peter Anvin,
	James Morse, Thomas Gleixner, linux-arm-kernel, Liang, Kan

On Fri, Mar 01, 2019 at 01:39:30PM +0000, Steven Price wrote:
> On 01/03/2019 12:30, Kirill A. Shutemov wrote:
> > On Fri, Mar 01, 2019 at 01:53:01PM +0200, Mike Rapoport wrote:
> >> Him Kirill,
> >>
> >> On Fri, Feb 22, 2019 at 12:06:18AM +0300, Kirill A. Shutemov wrote:
> >>> On Thu, Feb 21, 2019 at 05:16:46PM +0000, Steven Price wrote:
> >>>>>> Note that in terms of the new page walking code, these new defines are
> >>>>>> only used when walking a page table without a VMA (which isn't currently
> >>>>>> done), so architectures which don't use p?d_large currently will work
> >>>>>> fine with the generic versions. They only need to provide meaningful
> >>>>>> definitions when switching to use the walk-without-a-VMA functionality.
> >>>>>
> >>>>> How other architectures would know that they need to provide the helpers
> >>>>> to get walk-without-a-VMA functionality? This looks very fragile to me.
> >>>>
> >>>> Yes, you've got a good point there. This would apply to the p?d_large
> >>>> macros as well - any arch which (inadvertently) uses the generic version
> >>>> is likely to be fragile/broken.
> >>>>
> >>>> I think probably the best option here is to scrap the generic versions
> >>>> altogether and simply introduce a ARCH_HAS_PXD_LARGE config option which
> >>>> would enable the new functionality to those arches that opt-in. Do you
> >>>> think this would be less fragile?
> >>>
> >>> These helpers are useful beyond pagewalker.
> >>>
> >>> Can we actually do some grinding and make *all* archs to provide correct
> >>> helpers? Yes, it's tedious, but not that bad.
> >>
> >> Many architectures simply cannot support non-leaf entries at the higher
> >> levels. I think letting the use a generic helper actually does make sense.
> > 
> > I disagree.
> > 
> > It's makes sense if the level doesn't exists on the arch.
> 
> This is what patch 24 [1] of the series does - if the level doesn't
> exist then appropriate stubs are provided.
> 
> > But if the level exists, it will be less frugile to ask the arch to
> > provide the helper. Even if it is dummy always-false.
> 
> The problem (as I see it), is we need a reliable set of p?d_large()
> implementations to be able to walk arbitrary page tables. Either the
> entire functionality of walking page tables without a VMA has to be an
> opt-in per architecture, or we need to mandate that every architecture
> provide these implementations.

I agree that we need a reliable set of p?d_large(), but I'm still not
convinced that every architecture should provide these.

Why having generic versions if p?d_large() is more fragile, than e.g.
p??__access_permitted() or atomic ops?

IMHO, adding those functions/macros for architectures that support large
pages and providing defines to avoid override of 'static inline' implementations
would be robust enough and will avoid unnecessary stubs in architectures
that don't have large pages.
 
> I could provide an asm-generic header to provide a complete set of dummy
> implementations for architectures that don't support large pages at all,
> but that seems a bit overkill when most architectures only need to
> define 2 or 3 implementations (the rest being provided by the
> folded-levels automatically).
> 
> Thanks,
> 
> Steve
> 
> [1]
> https://lore.kernel.org/lkml/20190227170608.27963-25-steven.price@arm.com/

-- 
Sincerely yours,
Mike.


^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-03-03  7:12                   ` Mike Rapoport
@ 2019-03-04 14:35                     ` Steven Price
  2019-03-04 14:53                       ` Mike Rapoport
  0 siblings, 1 reply; 31+ messages in thread
From: Steven Price @ 2019-03-04 14:35 UTC (permalink / raw)
  To: Mike Rapoport
  Cc: Mark Rutland, Dave Hansen, James Morse, Arnd Bergmann,
	Ard Biesheuvel, Peter Zijlstra, Catalin Marinas, x86,
	Will Deacon, linux-kernel, linux-mm, Jérôme Glisse,
	Ingo Molnar, Borislav Petkov, Andy Lutomirski, H. Peter Anvin,
	Kirill A. Shutemov, Thomas Gleixner, linux-arm-kernel, Liang,
	Kan

On 03/03/2019 07:12, Mike Rapoport wrote:
> On Fri, Mar 01, 2019 at 01:39:30PM +0000, Steven Price wrote:
>> On 01/03/2019 12:30, Kirill A. Shutemov wrote:
>>> On Fri, Mar 01, 2019 at 01:53:01PM +0200, Mike Rapoport wrote:
>>>> Him Kirill,
>>>>
>>>> On Fri, Feb 22, 2019 at 12:06:18AM +0300, Kirill A. Shutemov wrote:
>>>>> On Thu, Feb 21, 2019 at 05:16:46PM +0000, Steven Price wrote:
>>>>>>>> Note that in terms of the new page walking code, these new defines are
>>>>>>>> only used when walking a page table without a VMA (which isn't currently
>>>>>>>> done), so architectures which don't use p?d_large currently will work
>>>>>>>> fine with the generic versions. They only need to provide meaningful
>>>>>>>> definitions when switching to use the walk-without-a-VMA functionality.
>>>>>>>
>>>>>>> How other architectures would know that they need to provide the helpers
>>>>>>> to get walk-without-a-VMA functionality? This looks very fragile to me.
>>>>>>
>>>>>> Yes, you've got a good point there. This would apply to the p?d_large
>>>>>> macros as well - any arch which (inadvertently) uses the generic version
>>>>>> is likely to be fragile/broken.
>>>>>>
>>>>>> I think probably the best option here is to scrap the generic versions
>>>>>> altogether and simply introduce a ARCH_HAS_PXD_LARGE config option which
>>>>>> would enable the new functionality to those arches that opt-in. Do you
>>>>>> think this would be less fragile?
>>>>>
>>>>> These helpers are useful beyond pagewalker.
>>>>>
>>>>> Can we actually do some grinding and make *all* archs to provide correct
>>>>> helpers? Yes, it's tedious, but not that bad.
>>>>
>>>> Many architectures simply cannot support non-leaf entries at the higher
>>>> levels. I think letting the use a generic helper actually does make sense.
>>>
>>> I disagree.
>>>
>>> It's makes sense if the level doesn't exists on the arch.
>>
>> This is what patch 24 [1] of the series does - if the level doesn't
>> exist then appropriate stubs are provided.
>>
>>> But if the level exists, it will be less frugile to ask the arch to
>>> provide the helper. Even if it is dummy always-false.
>>
>> The problem (as I see it), is we need a reliable set of p?d_large()
>> implementations to be able to walk arbitrary page tables. Either the
>> entire functionality of walking page tables without a VMA has to be an
>> opt-in per architecture, or we need to mandate that every architecture
>> provide these implementations.
> 
> I agree that we need a reliable set of p?d_large(), but I'm still not
> convinced that every architecture should provide these.
> 
> Why having generic versions if p?d_large() is more fragile, than e.g.
> p??__access_permitted() or atomic ops?

Personally I feel having p?d_large implemented for each arch has the
following benefits:

 * Matches p?d_present/p?d_none/p?d_bad which all similarly have to be
implemented for all arches except for folded levels (when folded using
the generic code).

 * Gives the architecture maintainers a heads-up and an opportunity to
ensure that the implementations I've written are correct rather than
silently picking up the generic version.

 * When adding a new architecture it will be obvious that p?d_large
implementations are needed.

The benefits of having a generic version seem to be:

 * No boiler plate for the architectures that don't support large pages
(saves a handful of lines).

 * Easier to merge (fewer patches).

While the last one is certainly appealing (to me at least), I'm not
convinced the benefits of the generic version outweigh those of
providing implementations per-arch.

Am I missing something?

> IMHO, adding those functions/macros for architectures that support large
> pages and providing defines to avoid override of 'static inline' implementations
> would be robust enough and will avoid unnecessary stubs in architectures
> that don't have large pages.

Clearly at run time there's no difference in the "robustness" - the code
generation should be the same. So it's purely down to development processes.

However, if you prefer I can resurrect the generic versions and drop the
patches that simply add dummy implementations.

Steve

^ permalink raw reply	[flat|nested] 31+ messages in thread

* Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros
  2019-03-04 14:35                     ` Steven Price
@ 2019-03-04 14:53                       ` Mike Rapoport
  0 siblings, 0 replies; 31+ messages in thread
From: Mike Rapoport @ 2019-03-04 14:53 UTC (permalink / raw)
  To: Steven Price
  Cc: Mark Rutland, Dave Hansen, James Morse, Arnd Bergmann,
	Ard Biesheuvel, Peter Zijlstra, Catalin Marinas, x86,
	Will Deacon, linux-kernel, linux-mm, Jérôme Glisse,
	Ingo Molnar, Borislav Petkov, Andy Lutomirski, H. Peter Anvin,
	Kirill A. Shutemov, Thomas Gleixner, linux-arm-kernel, Liang,
	Kan

On Mon, Mar 04, 2019 at 02:35:56PM +0000, Steven Price wrote:
> On 03/03/2019 07:12, Mike Rapoport wrote:
> > On Fri, Mar 01, 2019 at 01:39:30PM +0000, Steven Price wrote:
> >> On 01/03/2019 12:30, Kirill A. Shutemov wrote:
> >>> On Fri, Mar 01, 2019 at 01:53:01PM +0200, Mike Rapoport wrote:
> >>>> Him Kirill,
> >>>>
> >>>> On Fri, Feb 22, 2019 at 12:06:18AM +0300, Kirill A. Shutemov wrote:
> >>>>> On Thu, Feb 21, 2019 at 05:16:46PM +0000, Steven Price wrote:
> >>>>>>>> Note that in terms of the new page walking code, these new defines are
> >>>>>>>> only used when walking a page table without a VMA (which isn't currently
> >>>>>>>> done), so architectures which don't use p?d_large currently will work
> >>>>>>>> fine with the generic versions. They only need to provide meaningful
> >>>>>>>> definitions when switching to use the walk-without-a-VMA functionality.
> >>>>>>>
> >>>>>>> How other architectures would know that they need to provide the helpers
> >>>>>>> to get walk-without-a-VMA functionality? This looks very fragile to me.
> >>>>>>
> >>>>>> Yes, you've got a good point there. This would apply to the p?d_large
> >>>>>> macros as well - any arch which (inadvertently) uses the generic version
> >>>>>> is likely to be fragile/broken.
> >>>>>>
> >>>>>> I think probably the best option here is to scrap the generic versions
> >>>>>> altogether and simply introduce a ARCH_HAS_PXD_LARGE config option which
> >>>>>> would enable the new functionality to those arches that opt-in. Do you
> >>>>>> think this would be less fragile?
> >>>>>
> >>>>> These helpers are useful beyond pagewalker.
> >>>>>
> >>>>> Can we actually do some grinding and make *all* archs to provide correct
> >>>>> helpers? Yes, it's tedious, but not that bad.
> >>>>
> >>>> Many architectures simply cannot support non-leaf entries at the higher
> >>>> levels. I think letting the use a generic helper actually does make sense.
> >>>
> >>> I disagree.
> >>>
> >>> It's makes sense if the level doesn't exists on the arch.
> >>
> >> This is what patch 24 [1] of the series does - if the level doesn't
> >> exist then appropriate stubs are provided.
> >>
> >>> But if the level exists, it will be less frugile to ask the arch to
> >>> provide the helper. Even if it is dummy always-false.
> >>
> >> The problem (as I see it), is we need a reliable set of p?d_large()
> >> implementations to be able to walk arbitrary page tables. Either the
> >> entire functionality of walking page tables without a VMA has to be an
> >> opt-in per architecture, or we need to mandate that every architecture
> >> provide these implementations.
> > 
> > I agree that we need a reliable set of p?d_large(), but I'm still not
> > convinced that every architecture should provide these.
> > 
> > Why having generic versions if p?d_large() is more fragile, than e.g.
> > p??__access_permitted() or atomic ops?
> 
> Personally I feel having p?d_large implemented for each arch has the
> following benefits:
> 
>  * Matches p?d_present/p?d_none/p?d_bad which all similarly have to be
> implemented for all arches except for folded levels (when folded using
> the generic code).
> 
>  * Gives the architecture maintainers a heads-up and an opportunity to
> ensure that the implementations I've written are correct rather than
> silently picking up the generic version.
> 
>  * When adding a new architecture it will be obvious that p?d_large
> implementations are needed.
> 
> The benefits of having a generic version seem to be:
> 
>  * No boiler plate for the architectures that don't support large pages
> (saves a handful of lines).
> 
>  * Easier to merge (fewer patches).
> 
> While the last one is certainly appealing (to me at least), I'm not
> convinced the benefits of the generic version outweigh those of
> providing implementations per-arch.
> 
> Am I missing something?
> 
> > IMHO, adding those functions/macros for architectures that support large
> > pages and providing defines to avoid override of 'static inline' implementations
> > would be robust enough and will avoid unnecessary stubs in architectures
> > that don't have large pages.
> 
> Clearly at run time there's no difference in the "robustness" - the code
> generation should be the same. So it's purely down to development processes.
> 
> However, if you prefer I can resurrect the generic versions and drop the
> patches that simply add dummy implementations.

My concern was the code duplication, which didn't seem necessary. It's not
only about saving a handful of lines, but rather having as many of the code
shared by different architectures actually shared and not copied.

I'd really appreciate having the dummy versions in include/asm-generic
rather than all over arch/*/include/asm.
 
> Steve
> 

-- 
Sincerely yours,
Mike.


^ permalink raw reply	[flat|nested] 31+ messages in thread

end of thread, other threads:[~2019-03-04 14:53 UTC | newest]

Thread overview: 31+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-02-21 11:34 [PATCH v2 00/13] Convert x86 & arm64 to use generic page walk Steven Price
2019-02-21 11:34 ` [PATCH v2 01/13] arm64: mm: Add p?d_large() definitions Steven Price
2019-02-21 13:52   ` Mark Rutland
2019-02-21 11:34 ` [PATCH v2 02/13] x86/mm: " Steven Price
2019-02-21 14:21   ` Kirill A. Shutemov
2019-02-21 11:34 ` [PATCH v2 03/13] mm: Add generic p?d_large() macros Steven Price
2019-02-21 13:41   ` Mark Rutland
2019-02-21 14:28   ` Kirill A. Shutemov
2019-02-21 14:46     ` Steven Price
2019-02-21 14:57       ` Kirill A. Shutemov
2019-02-21 17:16         ` Steven Price
2019-02-21 21:06           ` Kirill A. Shutemov
2019-02-22 10:21             ` Steven Price
2019-03-01 11:53             ` Mike Rapoport
2019-03-01 12:30               ` Kirill A. Shutemov
2019-03-01 13:39                 ` Steven Price
2019-03-03  7:12                   ` Mike Rapoport
2019-03-04 14:35                     ` Steven Price
2019-03-04 14:53                       ` Mike Rapoport
2019-03-01 11:49         ` Mike Rapoport
2019-03-01 12:28           ` Kirill A. Shutemov
2019-02-21 11:34 ` [PATCH v2 04/13] mm: pagewalk: Add p4d_entry() and pgd_entry() Steven Price
2019-02-21 11:34 ` [PATCH v2 05/13] mm: pagewalk: Allow walking without vma Steven Price
2019-02-21 11:34 ` [PATCH v2 06/13] mm: pagewalk: Add 'depth' parameter to pte_hole Steven Price
2019-02-21 11:34 ` [PATCH v2 07/13] mm: pagewalk: Add test_p?d callbacks Steven Price
2019-02-21 11:34 ` [PATCH v2 08/13] arm64: mm: Convert mm/dump.c to use walk_page_range() Steven Price
2019-02-21 11:34 ` [PATCH v2 09/13] x86/mm: Point to struct seq_file from struct pg_state Steven Price
2019-02-21 11:34 ` [PATCH v2 10/13] x86/mm+efi: Convert ptdump_walk_pgd_level() to take a mm_struct Steven Price
2019-02-21 11:35 ` [PATCH v2 11/13] x86/mm: Convert ptdump_walk_pgd_level_debugfs() to take an mm_struct Steven Price
2019-02-21 11:35 ` [PATCH v2 12/13] x86/mm: Convert ptdump_walk_pgd_level_core() " Steven Price
2019-02-21 11:35 ` [PATCH v2 13/13] x86: mm: Convert dump_pagetables to use walk_page_range Steven Price

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