[PATCH v2 0/4] x86, mm: Handle large PAT bit in pud/pmd interfaces

[PATCH v2 0/4] x86, mm: Handle large PAT bit in pud/pmd interfaces

[Toshi Kani]

The PAT bit gets relocated to bit 12 when PUD and PMD mappings are used.
This bit 12, however, is not covered by PTE_FLAGS_MASK, which is corrently
used for masking pfn and flags for all cases.

Patch 1/4-2/4 make changes necessary for patch 3/4 to use P?D_PAGE_MASK.

Patch 3/4 fixes pud/pmd interfaces to handle the PAT bit when PUD and PMD
mappings are used.

Patch 3/4 fixes /sys/kernel/debug/kernel_page_tables to show the PAT bit
properly.

Note, the PAT bit is first enabled in 4.2-rc1 with WT mappings.

---
v2:
 - Change p?n_pfn() to handle the PAT bit. (Juergen Gross)
 - Mask pfn and flags with P?D_PAGE_MASK. (Juergen Gross)
 - Change p?d_page_vaddr() and p?d_page() to handle the PAT bit.

---
Toshi Kani (4):
  1/4 x86/vdso32: Define PGTABLE_LEVELS to 32bit VDSO
  2/4 x86, asm: Move PUD_PAGE macros to page_types.h
  3/4 x86: Fix pud/pmd interfaces to handle large PAT bit
  4/4 x86, mm: Fix page table dump to show PAT bit

---
4fa1ff9a08c...dd58e3d52618b00dd768de1753c35611906fcbee --stat
 arch/x86/entry/vdso/vdso32/vclock_gettime.c |  2 ++
 arch/x86/include/asm/page_64_types.h        |  3 ---
 arch/x86/include/asm/page_types.h           |  3 +++
 arch/x86/include/asm/pgtable.h              | 14 +++++-----
 arch/x86/include/asm/pgtable_types.h        | 40 ++++++++++++++++++++++++++---
 arch/x86/mm/dump_pagetables.c               | 39 +++++++++++++++-------------
 6 files changed, 70 insertions(+), 31 deletions(-)

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[PATCH v2 1/4] x86/vdso32: Define PGTABLE_LEVELS to 32bit VDSO

[Toshi Kani]

In case of CONFIG_X86_64, vdso32/vclock_gettime.c fakes a 32bit
kernel configuration by re-defining it to CONFIG_X86_32.  However,
it does not re-define CONFIG_PGTABLE_LEVELS leaving it as 4 levels.
Fix it by re-defining CONFIG_PGTABLE_LEVELS to 2 as X86_PAE is not
set.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
---
 arch/x86/entry/vdso/vdso32/vclock_gettime.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/entry/vdso/vdso32/vclock_gettime.c b/arch/x86/entry/vdso/vdso32/vclock_gettime.c
index 175cc72..87a86e0 100644
--- a/arch/x86/entry/vdso/vdso32/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vdso32/vclock_gettime.c
@@ -14,11 +14,13 @@
  */
 #undef CONFIG_64BIT
 #undef CONFIG_X86_64
+#undef CONFIG_PGTABLE_LEVELS
 #undef CONFIG_ILLEGAL_POINTER_VALUE
 #undef CONFIG_SPARSEMEM_VMEMMAP
 #undef CONFIG_NR_CPUS
 
 #define CONFIG_X86_32 1
+#define CONFIG_PGTABLE_LEVELS 2
 #define CONFIG_PAGE_OFFSET 0
 #define CONFIG_ILLEGAL_POINTER_VALUE 0
 #define CONFIG_NR_CPUS 1

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[PATCH v2 2/4] x86, asm: Move PUD_PAGE macros to page_types.h

[Toshi Kani]

PUD_SHIFT is defined according to a kernel configuration, which
allows it be commonly used by any kernels.  However, PUD_PAGE_SIZE
and PUD_PAGE_MASK, which are calculated from PUD_SHIFT, are defined
in page_64_types.h, which allows them be used by a 64-bit kernel
only.

Move PUD_PAGE_SIZE and PUD_PAGE_MASK to page_types.h so that they
can be used by any kernels as well.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
---
 arch/x86/include/asm/page_64_types.h |    3 ---
 arch/x86/include/asm/page_types.h    |    3 +++
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
index 4edd53b..4928cf0 100644
--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -26,9 +26,6 @@
 #define MCE_STACK 4
 #define N_EXCEPTION_STACKS 4  /* hw limit: 7 */
 
-#define PUD_PAGE_SIZE		(_AC(1, UL) << PUD_SHIFT)
-#define PUD_PAGE_MASK		(~(PUD_PAGE_SIZE-1))
-
 /*
  * Set __PAGE_OFFSET to the most negative possible address +
  * PGDIR_SIZE*16 (pgd slot 272).  The gap is to allow a space for a
diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h
index c7c712f..c5b7fb2 100644
--- a/arch/x86/include/asm/page_types.h
+++ b/arch/x86/include/asm/page_types.h
@@ -20,6 +20,9 @@
 #define PMD_PAGE_SIZE		(_AC(1, UL) << PMD_SHIFT)
 #define PMD_PAGE_MASK		(~(PMD_PAGE_SIZE-1))
 
+#define PUD_PAGE_SIZE		(_AC(1, UL) << PUD_SHIFT)
+#define PUD_PAGE_MASK		(~(PUD_PAGE_SIZE-1))
+
 #define HPAGE_SHIFT		PMD_SHIFT
 #define HPAGE_SIZE		(_AC(1,UL) << HPAGE_SHIFT)
 #define HPAGE_MASK		(~(HPAGE_SIZE - 1))

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[PATCH v2 3/4] x86: Fix pud/pmd interfaces to handle large PAT bit

[Toshi Kani]

The PAT bit gets relocated to bit 12 when PUD and PMD mappings are
used.  This bit 12, however, is not covered by PTE_FLAGS_MASK, which
is corrently used for masking pfn and flags for all cases.

Fix pud/pmd interfaces to handle pfn and flags properly by using
P?D_PAGE_MASK when PUD/PMD mappings are used, i.e. PSE bit is set.

Suggested-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Konrad Wilk <konrad.wilk@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
 arch/x86/include/asm/pgtable.h       |   14 +++++++-----
 arch/x86/include/asm/pgtable_types.h |   40 +++++++++++++++++++++++++++++++---
 2 files changed, 44 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 867da5b..0733ec7 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -142,12 +142,12 @@ static inline unsigned long pte_pfn(pte_t pte)
 
 static inline unsigned long pmd_pfn(pmd_t pmd)
 {
-	return (pmd_val(pmd) & PTE_PFN_MASK) >> PAGE_SHIFT;
+	return (pmd_val(pmd) & pmd_pfn_mask(pmd)) >> PAGE_SHIFT;
 }
 
 static inline unsigned long pud_pfn(pud_t pud)
 {
-	return (pud_val(pud) & PTE_PFN_MASK) >> PAGE_SHIFT;
+	return (pud_val(pud) & pud_pfn_mask(pud)) >> PAGE_SHIFT;
 }
 
 #define pte_page(pte)	pfn_to_page(pte_pfn(pte))
@@ -502,14 +502,15 @@ static inline int pmd_none(pmd_t pmd)
 
 static inline unsigned long pmd_page_vaddr(pmd_t pmd)
 {
-	return (unsigned long)__va(pmd_val(pmd) & PTE_PFN_MASK);
+	return (unsigned long)__va(pmd_val(pmd) & pmd_pfn_mask(pmd));
 }
 
 /*
  * Currently stuck as a macro due to indirect forward reference to
  * linux/mmzone.h's __section_mem_map_addr() definition:
  */
-#define pmd_page(pmd)	pfn_to_page((pmd_val(pmd) & PTE_PFN_MASK) >> PAGE_SHIFT)
+#define pmd_page(pmd)		\
+	pfn_to_page((pmd_val(pmd) & pmd_pfn_mask(pmd)) >> PAGE_SHIFT)
 
 /*
  * the pmd page can be thought of an array like this: pmd_t[PTRS_PER_PMD]
@@ -570,14 +571,15 @@ static inline int pud_present(pud_t pud)
 
 static inline unsigned long pud_page_vaddr(pud_t pud)
 {
-	return (unsigned long)__va((unsigned long)pud_val(pud) & PTE_PFN_MASK);
+	return (unsigned long)__va(pud_val(pud) & pud_pfn_mask(pud));
 }
 
 /*
  * Currently stuck as a macro due to indirect forward reference to
  * linux/mmzone.h's __section_mem_map_addr() definition:
  */
-#define pud_page(pud)		pfn_to_page(pud_val(pud) >> PAGE_SHIFT)
+#define pud_page(pud)		\
+	pfn_to_page((pud_val(pud) & pud_pfn_mask(pud)) >> PAGE_SHIFT)
 
 /* Find an entry in the second-level page table.. */
 static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address)
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 13f310b..dd5b0aa 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -209,10 +209,10 @@ enum page_cache_mode {
 
 #include <linux/types.h>
 
-/* PTE_PFN_MASK extracts the PFN from a (pte|pmd|pud|pgd)val_t */
+/* Extracts the PFN from a (pte|pmd|pud|pgd)val_t of a 4KB page */
 #define PTE_PFN_MASK		((pteval_t)PHYSICAL_PAGE_MASK)
 
-/* PTE_FLAGS_MASK extracts the flags from a (pte|pmd|pud|pgd)val_t */
+/* Extracts the flags from a (pte|pmd|pud|pgd)val_t of a 4KB page */
 #define PTE_FLAGS_MASK		(~PTE_PFN_MASK)
 
 typedef struct pgprot { pgprotval_t pgprot; } pgprot_t;
@@ -276,14 +276,46 @@ static inline pmdval_t native_pmd_val(pmd_t pmd)
 }
 #endif
 
+static inline pudval_t pud_pfn_mask(pud_t pud)
+{
+	if (native_pud_val(pud) & _PAGE_PSE)
+		return PUD_PAGE_MASK & PHYSICAL_PAGE_MASK;
+	else
+		return PTE_PFN_MASK;
+}
+
+static inline pudval_t pud_flags_mask(pud_t pud)
+{
+	if (native_pud_val(pud) & _PAGE_PSE)
+		return ~(PUD_PAGE_MASK & (pudval_t)PHYSICAL_PAGE_MASK);
+	else
+		return ~PTE_PFN_MASK;
+}
+
 static inline pudval_t pud_flags(pud_t pud)
 {
-	return native_pud_val(pud) & PTE_FLAGS_MASK;
+	return native_pud_val(pud) & pud_flags_mask(pud);
+}
+
+static inline pmdval_t pmd_pfn_mask(pmd_t pmd)
+{
+	if (native_pmd_val(pmd) & _PAGE_PSE)
+		return PMD_PAGE_MASK & PHYSICAL_PAGE_MASK;
+	else
+		return PTE_PFN_MASK;
+}
+
+static inline pmdval_t pmd_flags_mask(pmd_t pmd)
+{
+	if (native_pmd_val(pmd) & _PAGE_PSE)
+		return ~(PMD_PAGE_MASK & (pmdval_t)PHYSICAL_PAGE_MASK);
+	else
+		return ~PTE_PFN_MASK;
 }
 
 static inline pmdval_t pmd_flags(pmd_t pmd)
 {
-	return native_pmd_val(pmd) & PTE_FLAGS_MASK;
+	return native_pmd_val(pmd) & pmd_flags_mask(pmd);
 }
 
 static inline pte_t native_make_pte(pteval_t val)

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[PATCH v2 4/4] x86, mm: Fix page table dump to show PAT bit

[Toshi Kani]

/sys/kernel/debug/kernel_page_tables does not show the PAT bit
for PUD and PMD mappings.  This is because walk_pud_level(),
walk_pmd_level() and note_page() mask the flags with PTE_FLAGS_MASK,
which does not cover their PAT bit, _PAGE_PAT_LARGE.

Fix it by replacing the use of PTE_FLAGS_MASK with p?d_flags(),
which masks the flags properly.

Change also to show the PAT bit as "PAT" to be consistent with
other bits.

Reported-by: Robert Elliott <elliott@hp.com>
Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Robert Elliott <elliott@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
 arch/x86/mm/dump_pagetables.c |   39 +++++++++++++++++++++------------------
 1 file changed, 21 insertions(+), 18 deletions(-)

diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index f0cedf3..71ab2d7 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -155,7 +155,7 @@ static void printk_prot(struct seq_file *m, pgprot_t prot, int level, bool dmsg)
 			pt_dump_cont_printf(m, dmsg, "    ");
 		if ((level == 4 && pr & _PAGE_PAT) ||
 		    ((level == 3 || level == 2) && pr & _PAGE_PAT_LARGE))
-			pt_dump_cont_printf(m, dmsg, "pat ");
+			pt_dump_cont_printf(m, dmsg, "PAT ");
 		else
 			pt_dump_cont_printf(m, dmsg, "    ");
 		if (pr & _PAGE_GLOBAL)
@@ -198,8 +198,8 @@ static void note_page(struct seq_file *m, struct pg_state *st,
 	 * we have now. "break" is either changing perms, levels or
 	 * address space marker.
 	 */
-	prot = pgprot_val(new_prot) & PTE_FLAGS_MASK;
-	cur = pgprot_val(st->current_prot) & PTE_FLAGS_MASK;
+	prot = pgprot_val(new_prot);
+	cur = pgprot_val(st->current_prot);
 
 	if (!st->level) {
 		/* First entry */
@@ -269,13 +269,13 @@ static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
 {
 	int i;
 	pte_t *start;
+	pgprotval_t prot;
 
 	start = (pte_t *) pmd_page_vaddr(addr);
 	for (i = 0; i < PTRS_PER_PTE; i++) {
-		pgprot_t prot = pte_pgprot(*start);
-
+		prot = pte_flags(*start);
 		st->current_address = normalize_addr(P + i * PTE_LEVEL_MULT);
-		note_page(m, st, prot, 4);
+		note_page(m, st, __pgprot(prot), 4);
 		start++;
 	}
 }
@@ -287,18 +287,19 @@ static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr,
 {
 	int i;
 	pmd_t *start;
+	pgprotval_t prot;
 
 	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)) {
-			pgprotval_t prot = pmd_val(*start) & PTE_FLAGS_MASK;
-
-			if (pmd_large(*start) || !pmd_present(*start))
+			if (pmd_large(*start) || !pmd_present(*start)) {
+				prot = pmd_flags(*start);
 				note_page(m, st, __pgprot(prot), 3);
-			else
+			} else {
 				walk_pte_level(m, st, *start,
 					       P + i * PMD_LEVEL_MULT);
+			}
 		} else
 			note_page(m, st, __pgprot(0), 3);
 		start++;
@@ -318,19 +319,20 @@ static void walk_pud_level(struct seq_file *m, struct pg_state *st, pgd_t addr,
 {
 	int i;
 	pud_t *start;
+	pgprotval_t prot;
 
 	start = (pud_t *) pgd_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)) {
-			pgprotval_t prot = pud_val(*start) & PTE_FLAGS_MASK;
-
-			if (pud_large(*start) || !pud_present(*start))
+			if (pud_large(*start) || !pud_present(*start)) {
+				prot = pud_flags(*start);
 				note_page(m, st, __pgprot(prot), 2);
-			else
+			} else {
 				walk_pmd_level(m, st, *start,
 					       P + i * PUD_LEVEL_MULT);
+			}
 		} else
 			note_page(m, st, __pgprot(0), 2);
 
@@ -351,6 +353,7 @@ void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd)
 #else
 	pgd_t *start = swapper_pg_dir;
 #endif
+	pgprotval_t prot;
 	int i;
 	struct pg_state st = {};
 
@@ -362,13 +365,13 @@ void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd)
 	for (i = 0; i < PTRS_PER_PGD; i++) {
 		st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
 		if (!pgd_none(*start)) {
-			pgprotval_t prot = pgd_val(*start) & PTE_FLAGS_MASK;
-
-			if (pgd_large(*start) || !pgd_present(*start))
+			if (pgd_large(*start) || !pgd_present(*start)) {
+				prot = pgd_flags(*start);
 				note_page(m, &st, __pgprot(prot), 1);
-			else
+			} else {
 				walk_pud_level(m, &st, *start,
 					       i * PGD_LEVEL_MULT);
+			}
 		} else
 			note_page(m, &st, __pgprot(0), 1);
 

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Re: [PATCH v2 0/4] x86, mm: Handle large PAT bit in pud/pmd interfaces

[Ingo Molnar]

* Toshi Kani <toshi.kani@hp.com> wrote:

> The PAT bit gets relocated to bit 12 when PUD and PMD mappings are used.
> This bit 12, however, is not covered by PTE_FLAGS_MASK, which is corrently
> used for masking pfn and flags for all cases.
> 
> Patch 1/4-2/4 make changes necessary for patch 3/4 to use P?D_PAGE_MASK.
> 
> Patch 3/4 fixes pud/pmd interfaces to handle the PAT bit when PUD and PMD
> mappings are used.
> 
> Patch 3/4 fixes /sys/kernel/debug/kernel_page_tables to show the PAT bit
> properly.
> 
> Note, the PAT bit is first enabled in 4.2-rc1 with WT mappings.

Are patches 1-3 only needed to fix /sys/kernel/debug/kernel_page_tables output, or 
are there other things fixed as well? The patches do not tell us any of that 
information ...

Thanks,

	Ingo

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Re: [PATCH v2 0/4] x86, mm: Handle large PAT bit in pud/pmd interfaces

[Toshi Kani]

On Tue, 2015-07-21 at 10:05 +0200, Ingo Molnar wrote:
> * Toshi Kani <toshi.kani@hp.com> wrote:
> 
> > The PAT bit gets relocated to bit 12 when PUD and PMD mappings are 
> > used.
> > This bit 12, however, is not covered by PTE_FLAGS_MASK, which is 
> > corrently
> > used for masking pfn and flags for all cases.
> > 
> > Patch 1/4-2/4 make changes necessary for patch 3/4 to use 
> > P?D_PAGE_MASK.
> > 
> > Patch 3/4 fixes pud/pmd interfaces to handle the PAT bit when PUD and 
> > PMD
> > mappings are used.
> > 
> > Patch 3/4 fixes /sys/kernel/debug/kernel_page_tables to show the PAT 
> > bit
> > properly.
> > 
> > Note, the PAT bit is first enabled in 4.2-rc1 with WT mappings.
> 
> Are patches 1-3 only needed to fix /sys/kernel/debug/kernel_page_tables 
> output, or 
> are there other things fixed as well? The patches do not tell us any of 
> that information ...

Patch 3 (and patch 1-2 needed for patch 3) fixes multiple pud/pmd
interfaces to work properly with _PAGE_PAT_LARGE bit set.  Because pmem is
the only module that can create a range with this bit set with large page
WT maps in 4.2, this issue has not been exposed other than the case in
kernel_page_tables fixed by patch 4.  Since there can be other cases in
future, all patches should go to 4.2 to prevent them to happen.  There is
no issue in 4.1 & older since they cannot set the bit.

Thanks,
-Toshi

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