[PATCH v11 0/12] Support Write-Through mapping on x86

[PATCH v11 0/12] Support Write-Through mapping on x86

[Toshi Kani]

This patchset adds support of Write-Through (WT) mapping on x86.
The study below shows that using WT mapping may be useful for
non-volatile memory.

http://www.hpl.hp.com/techreports/2012/HPL-2012-236.pdf

The patchset consists of the following changes.
 - Patch 1/12 to 2/12 refactor !pat_enable paths
 - Patch 3/12 to 8/12 add ioremap_wt()
 - Patch 9/12 adds pgprot_writethrough()
 - Patch 10/12 to 11/12 add set_memory_wt()
 - Patch 12/12 changes the pmem driver to call ioremap_wt()

All new/modified interfaces have been tested.

---
v11:
- Reordered the refactor changes from patch 10-11 to 1-2.
  (Borislav Petkov)
- Changed BUG() to panic(). (Borislav Petkov)
- Rebased to tip/master and resolved conflicts. 

v10:
- Removed ioremap_writethrough(). (Thomas Gleixner)
- Clarified and cleaned up multiple comments and functions.
  (Thomas Gleixner) 
- Changed ioremap_change_attr() to accept the WT type.

v9:
- Changed to export the set_xxx_wt() interfaces with GPL.
  (Ingo Molnar)
- Changed is_new_memtype_allowed() to handle WT cases.
- Changed arch-specific io.h to define ioremap_wt().
- Changed the pmem driver to use ioremap_wt().
- Rebased to 4.1-rc3 and resolved minor conflicts.

v8:
- Rebased to 4.0-rc1 and resolved conflicts with 9d34cfdf4 in
  patch 5/7.

v7:
- Rebased to 3.19-rc3 as Juergen's patchset for the PAT management
  has been accepted.

v6:
- Dropped the patch moving [set|get]_page_memtype() to pat.c
  since the tip branch already has this change.
- Fixed an issue when CONFIG_X86_PAT is not defined.

v5:
- Clarified comment of why using slot 7. (Andy Lutomirski,
  Thomas Gleixner)
- Moved [set|get]_page_memtype() to pat.c. (Thomas Gleixner)
- Removed BUG() from set_page_memtype(). (Thomas Gleixner)

v4:
- Added set_memory_wt() by adding WT support of regular memory.

v3:
- Dropped the set_memory_wt() patch. (Andy Lutomirski)
- Refactored the !pat_enabled handling. (H. Peter Anvin,
  Andy Lutomirski)
- Added the picture of PTE encoding. (Konrad Rzeszutek Wilk)

v2:
- Changed WT to use slot 7 of the PAT MSR. (H. Peter Anvin,
  Andy Lutomirski)
- Changed to have conservative checks to exclude all Pentium 2, 3,
  M, and 4 families. (Ingo Molnar, Henrique de Moraes Holschuh,
  Andy Lutomirski)
- Updated documentation to cover WT interfaces and usages.
  (Andy Lutomirski, Yigal Korman)

---
Toshi Kani (12):
 1/12 x86, mm, pat: Cleanup init flags in pat_init()
 2/12 x86, mm, pat: Refactor !pat_enable handling
 3/12 x86, mm, pat: Set WT to PA7 slot of PAT MSR
 4/12 x86, mm, pat: Change reserve_memtype() for WT
 5/12 x86, asm: Change is_new_memtype_allowed() for WT
 6/12 x86, mm, asm-gen: Add ioremap_wt() for WT
 7/12 arch/*/asm/io.h: Add ioremap_wt() to all architectures
 8/12 video/fbdev, asm/io.h: Remove ioremap_writethrough()
 9/12 x86, mm, pat: Add pgprot_writethrough() for WT
10/12 x86, mm, asm: Add WT support to set_page_memtype()
11/12 x86, mm: Add set_memory_wt() for WT
12/12 drivers/block/pmem: Map NVDIMM with ioremap_wt()

---
 Documentation/x86/pat.txt            |  13 +-
 arch/arc/include/asm/io.h            |   1 +
 arch/arm/include/asm/io.h            |   1 +
 arch/arm64/include/asm/io.h          |   1 +
 arch/avr32/include/asm/io.h          |   1 +
 arch/frv/include/asm/io.h            |   4 +-
 arch/m32r/include/asm/io.h           |   1 +
 arch/m68k/include/asm/io_mm.h        |   4 +-
 arch/m68k/include/asm/io_no.h        |   4 +-
 arch/metag/include/asm/io.h          |   3 +
 arch/microblaze/include/asm/io.h     |   2 +-
 arch/mn10300/include/asm/io.h        |   1 +
 arch/nios2/include/asm/io.h          |   1 +
 arch/s390/include/asm/io.h           |   1 +
 arch/sparc/include/asm/io_32.h       |   1 +
 arch/sparc/include/asm/io_64.h       |   1 +
 arch/tile/include/asm/io.h           |   2 +-
 arch/x86/include/asm/cacheflush.h    |   6 +-
 arch/x86/include/asm/io.h            |   2 +
 arch/x86/include/asm/pgtable.h       |   8 +-
 arch/x86/include/asm/pgtable_types.h |   3 +
 arch/x86/mm/init.c                   |   6 +-
 arch/x86/mm/iomap_32.c               |  12 +-
 arch/x86/mm/ioremap.c                |  29 ++++-
 arch/x86/mm/pageattr.c               |  65 +++++++---
 arch/x86/mm/pat.c                    | 229 +++++++++++++++++++++++------------
 arch/xtensa/include/asm/io.h         |   1 +
 drivers/block/pmem.c                 |   4 +-
 drivers/video/fbdev/amifb.c          |   4 +-
 drivers/video/fbdev/atafb.c          |   3 +-
 drivers/video/fbdev/hpfb.c           |   4 +-
 include/asm-generic/io.h             |   9 ++
 include/asm-generic/iomap.h          |   4 +
 include/asm-generic/pgtable.h        |   4 +
 34 files changed, 310 insertions(+), 125 deletions(-)

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[PATCH v11 1/12] x86, mm, pat: Cleanup init flags in pat_init()

[Toshi Kani]

From: Toshi Kani <toshi.kani@hp.com>

pat_init() uses two flags, 'boot_cpu' and 'boot_pat_state', for
tracking the boot CPU's initialization status.  'boot_pat_state'
is also overloaded to carry the boot PAT value.

This patch cleans this up by replacing them with a new single
flag, 'boot_cpu_done', to track the boot CPU's initialization
status.  'boot_pat_state' is only used to carry the boot PAT
value as a result.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
 arch/x86/mm/pat.c |   40 +++++++++++++++++++---------------------
 1 file changed, 19 insertions(+), 21 deletions(-)

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index a1c9654..e1ec6a7 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -197,24 +197,29 @@ void pat_init_cache_modes(void)
 void pat_init(void)
 {
 	u64 pat;
-	bool boot_cpu = !boot_pat_state;
+	static bool boot_cpu_done;
 
 	if (!pat_enabled())
 		return;
 
-	if (!cpu_has_pat) {
-		if (!boot_pat_state) {
+	if (!boot_cpu_done) {
+		if (!cpu_has_pat) {
 			pat_disable("PAT not supported by CPU.");
 			return;
-		} else {
-			/*
-			 * If this happens we are on a secondary CPU, but
-			 * switched to PAT on the boot CPU. We have no way to
-			 * undo PAT.
-			 */
-			pr_err("x86/PAT: PAT enabled, but not supported by secondary CPU\n");
-			BUG();
 		}
+
+		rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
+		if (!boot_pat_state) {
+			pat_disable("PAT read returns always zero, disabled.");
+			return;
+		}
+	} else if (!cpu_has_pat) {
+		/*
+		 * If this happens we are on a secondary CPU, but
+		 * switched to PAT on the boot CPU. We have no way to
+		 * undo PAT.
+		 */
+		panic("PAT enabled, but not supported by secondary CPU\n");
 	}
 
 	/* Set PWT to Write-Combining. All other bits stay the same */
@@ -233,19 +238,12 @@ void pat_init(void)
 	pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
 	      PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
 
-	/* Boot CPU check */
-	if (!boot_pat_state) {
-		rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
-		if (!boot_pat_state) {
-			pat_disable("PAT read returns always zero, disabled.");
-			return;
-		}
-	}
-
 	wrmsrl(MSR_IA32_CR_PAT, pat);
 
-	if (boot_cpu)
+	if (!boot_cpu_done) {
 		pat_init_cache_modes();
+		boot_cpu_done = true;
+	}
 }
 
 #undef PAT

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[PATCH v11 2/12] x86, mm, pat: Refactor !pat_enabled handling

[Toshi Kani]

From: Toshi Kani <toshi.kani@hp.com>

This patch refactors the !pat_enabled code paths and integrates
them into the PAT abstraction code.  The PAT table is emulated by
corresponding to the two cache attribute bits, PWT (Write Through)
and PCD (Cache Disable).  The emulated PAT table is the same as the
BIOS default setup when the system has PAT but the "nopat" boot
option is specified.  The emulated PAT table is also used when
MSR_IA32_CR_PAT returns 0 -- 9d34cfdf4796 ("x86: Don't rely on
VMWare emulating PAT MSR correctly").

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/mm/init.c     |    6 ++-
 arch/x86/mm/iomap_32.c |   12 +++---
 arch/x86/mm/ioremap.c  |    5 +--
 arch/x86/mm/pageattr.c |    3 --
 arch/x86/mm/pat.c      |   95 +++++++++++++++++++++++++++++-------------------
 5 files changed, 67 insertions(+), 54 deletions(-)

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 1d55318..8533b46 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -40,7 +40,7 @@
  */
 uint16_t __cachemode2pte_tbl[_PAGE_CACHE_MODE_NUM] = {
 	[_PAGE_CACHE_MODE_WB      ]	= 0         | 0        ,
-	[_PAGE_CACHE_MODE_WC      ]	= _PAGE_PWT | 0        ,
+	[_PAGE_CACHE_MODE_WC      ]	= 0         | _PAGE_PCD,
 	[_PAGE_CACHE_MODE_UC_MINUS]	= 0         | _PAGE_PCD,
 	[_PAGE_CACHE_MODE_UC      ]	= _PAGE_PWT | _PAGE_PCD,
 	[_PAGE_CACHE_MODE_WT      ]	= 0         | _PAGE_PCD,
@@ -50,11 +50,11 @@ EXPORT_SYMBOL(__cachemode2pte_tbl);
 
 uint8_t __pte2cachemode_tbl[8] = {
 	[__pte2cm_idx( 0        | 0         | 0        )] = _PAGE_CACHE_MODE_WB,
-	[__pte2cm_idx(_PAGE_PWT | 0         | 0        )] = _PAGE_CACHE_MODE_WC,
+	[__pte2cm_idx(_PAGE_PWT | 0         | 0        )] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx( 0        | _PAGE_PCD | 0        )] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | 0        )] = _PAGE_CACHE_MODE_UC,
 	[__pte2cm_idx( 0        | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_WB,
-	[__pte2cm_idx(_PAGE_PWT | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_WC,
+	[__pte2cm_idx(_PAGE_PWT | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx(0         | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC,
 };
diff --git a/arch/x86/mm/iomap_32.c b/arch/x86/mm/iomap_32.c
index 37d2ba2..9c0ff04 100644
--- a/arch/x86/mm/iomap_32.c
+++ b/arch/x86/mm/iomap_32.c
@@ -78,13 +78,13 @@ void __iomem *
 iomap_atomic_prot_pfn(unsigned long pfn, pgprot_t prot)
 {
 	/*
-	 * For non-PAT systems, promote PAGE_KERNEL_WC to PAGE_KERNEL_UC_MINUS.
-	 * PAGE_KERNEL_WC maps to PWT, which translates to uncached if the
-	 * MTRR is UC or WC.  UC_MINUS gets the real intention, of the
-	 * user, which is "WC if the MTRR is WC, UC if you can't do that."
+	 * For non-PAT systems, translate non-WB request to UC- just in
+	 * case the caller set the PWT bit to prot directly without using
+	 * pgprot_writecombine(). UC- translates to uncached if the MTRR
+	 * is UC or WC. UC- gets the real intention, of the user, which is
+	 * "WC if the MTRR is WC, UC if you can't do that."
 	 */
-	if (!pat_enabled() && pgprot_val(prot) ==
-	    (__PAGE_KERNEL | cachemode2protval(_PAGE_CACHE_MODE_WC)))
+	if (!pat_enabled() && pgprot2cachemode(prot) != _PAGE_CACHE_MODE_WB)
 		prot = __pgprot(__PAGE_KERNEL |
 				cachemode2protval(_PAGE_CACHE_MODE_UC_MINUS));
 
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 938609e..078c270 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -292,11 +292,8 @@ EXPORT_SYMBOL_GPL(ioremap_uc);
  */
 void __iomem *ioremap_wc(resource_size_t phys_addr, unsigned long size)
 {
-	if (pat_enabled())
-		return __ioremap_caller(phys_addr, size, _PAGE_CACHE_MODE_WC,
+	return __ioremap_caller(phys_addr, size, _PAGE_CACHE_MODE_WC,
 					__builtin_return_address(0));
-	else
-		return ioremap_nocache(phys_addr, size);
 }
 EXPORT_SYMBOL(ioremap_wc);
 
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 70d221f..94aae76 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1571,9 +1571,6 @@ int set_memory_wc(unsigned long addr, int numpages)
 {
 	int ret;
 
-	if (!pat_enabled())
-		return set_memory_uc(addr, numpages);
-
 	ret = reserve_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE,
 		_PAGE_CACHE_MODE_WC, NULL);
 	if (ret)
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index e1ec6a7..819ae28 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -182,7 +182,11 @@ void pat_init_cache_modes(void)
 	char pat_msg[33];
 	u64 pat;
 
-	rdmsrl(MSR_IA32_CR_PAT, pat);
+	if (pat_enabled())
+		rdmsrl(MSR_IA32_CR_PAT, pat);
+	else
+		pat = boot_pat_state;
+
 	pat_msg[32] = 0;
 	for (i = 7; i >= 0; i--) {
 		cache = pat_get_cache_mode((pat >> (i * 8)) & 7,
@@ -199,21 +203,16 @@ void pat_init(void)
 	u64 pat;
 	static bool boot_cpu_done;
 
-	if (!pat_enabled())
-		return;
-
 	if (!boot_cpu_done) {
-		if (!cpu_has_pat) {
+		if (!cpu_has_pat)
 			pat_disable("PAT not supported by CPU.");
-			return;
-		}
 
-		rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
-		if (!boot_pat_state) {
-			pat_disable("PAT read returns always zero, disabled.");
-			return;
+		if (pat_enabled()) {
+			rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
+			if (!boot_pat_state)
+				pat_disable("PAT read returns always zero, disabled.");
 		}
-	} else if (!cpu_has_pat) {
+	} else if (!cpu_has_pat && pat_enabled()) {
 		/*
 		 * If this happens we are on a secondary CPU, but
 		 * switched to PAT on the boot CPU. We have no way to
@@ -222,23 +221,50 @@ void pat_init(void)
 		panic("PAT enabled, but not supported by secondary CPU\n");
 	}
 
-	/* Set PWT to Write-Combining. All other bits stay the same */
-	/*
-	 * PTE encoding used in Linux:
-	 *      PAT
-	 *      |PCD
-	 *      ||PWT
-	 *      |||
-	 *      000 WB		_PAGE_CACHE_WB
-	 *      001 WC		_PAGE_CACHE_WC
-	 *      010 UC-		_PAGE_CACHE_UC_MINUS
-	 *      011 UC		_PAGE_CACHE_UC
-	 * PAT bit unused
-	 */
-	pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
-	      PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
+	if (!pat_enabled()) {
+		/*
+		 * No PAT. Emulate the PAT table that corresponds to the two
+		 * cache bits, PWT (Write Through) and PCD (Cache Disable).
+		 * This setup is the same as the BIOS default setup when the
+		 * system has PAT but the "nopat" boot option is specified.
+		 * This emulated PAT table is also used when MSR_IA32_CR_PAT
+		 * returns 0.
+		 *
+		 *  PTE encoding used in Linux:
+		 *       PCD
+		 *       |PWT  PAT
+		 *       ||    slot
+		 *       00    0    WB : _PAGE_CACHE_MODE_WB
+		 *       01    1    WT : _PAGE_CACHE_MODE_WT
+		 *       10    2    UC-: _PAGE_CACHE_MODE_UC_MINUS
+		 *       11    3    UC : _PAGE_CACHE_MODE_UC
+		 *
+		 * NOTE: When WC or WP is used, it is redirected to UC- per
+		 * the default setup in __cachemode2pte_tbl[].
+		 */
+		pat = PAT(0, WB) | PAT(1, WT) | PAT(2, UC_MINUS) | PAT(3, UC) |
+		      PAT(4, WB) | PAT(5, WT) | PAT(6, UC_MINUS) | PAT(7, UC);
+		if (!boot_pat_state)
+			boot_pat_state = pat;
+	} else {
+		/*
+		 * PTE encoding used in Linux:
+		 *      PAT
+		 *      |PCD
+		 *      ||PWT
+		 *      |||
+		 *      000 WB		_PAGE_CACHE_WB
+		 *      001 WC		_PAGE_CACHE_WC
+		 *      010 UC-		_PAGE_CACHE_UC_MINUS
+		 *      011 UC		_PAGE_CACHE_UC
+		 * PAT bit unused
+		 */
+		pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
+		      PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
+	}
 
-	wrmsrl(MSR_IA32_CR_PAT, pat);
+	if (pat_enabled())
+		wrmsrl(MSR_IA32_CR_PAT, pat);
 
 	if (!boot_cpu_done) {
 		pat_init_cache_modes();
@@ -400,12 +426,8 @@ int reserve_memtype(u64 start, u64 end, enum page_cache_mode req_type,
 
 	if (!pat_enabled()) {
 		/* This is identical to page table setting without PAT */
-		if (new_type) {
-			if (req_type == _PAGE_CACHE_MODE_WC)
-				*new_type = _PAGE_CACHE_MODE_UC_MINUS;
-			else
-				*new_type = req_type;
-		}
+		if (new_type)
+			*new_type = req_type;
 		return 0;
 	}
 
@@ -909,11 +931,8 @@ void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
 
 pgprot_t pgprot_writecombine(pgprot_t prot)
 {
-	if (pat_enabled())
-		return __pgprot(pgprot_val(prot) |
+	return __pgprot(pgprot_val(prot) |
 				cachemode2protval(_PAGE_CACHE_MODE_WC));
-	else
-		return pgprot_noncached(prot);
 }
 EXPORT_SYMBOL_GPL(pgprot_writecombine);
 

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[PATCH v11 3/12] x86, mm, pat: Set WT to PA7 slot of PAT MSR

[Toshi Kani]

From: Toshi Kani <toshi.kani@hp.com>

This patch sets WT to the PA7 slot in the PAT MSR when the processor
is not affected by the PAT errata.  The PA7 slot is chosen to improve
robustness in the presence of errata that might cause the high PAT bit
to be ignored.  This way a buggy PA7 slot access will hit the PA3 slot,
which is UC, so at worst we lose performance without causing a correctness
issue.

The following Intel processors are affected by the PAT errata.

   errata               cpuid
   ----------------------------------------------------
   Pentium 2, A52       family 0x6, model 0x5
   Pentium 3, E27       family 0x6, model 0x7, 0x8
   Pentium 3 Xenon, G26 family 0x6, model 0x7, 0x8, 0xa
   Pentium M, Y26       family 0x6, model 0x9
   Pentium M 90nm, X9   family 0x6, model 0xd
   Pentium 4, N46       family 0xf, model 0x0

Instead of making sharp boundary checks, this patch makes conservative
checks to exclude all Pentium 2, 3, M and 4 family processors.  For
such processors, _PAGE_CACHE_MODE_WT is redirected to UC- per the
default setup in __cachemode2pte_tbl[].

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/mm/pat.c |   57 ++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 49 insertions(+), 8 deletions(-)

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 819ae28..3d9f125 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -201,6 +201,7 @@ void pat_init_cache_modes(void)
 void pat_init(void)
 {
 	u64 pat;
+	struct cpuinfo_x86 *c = &boot_cpu_data;
 	static bool boot_cpu_done;
 
 	if (!boot_cpu_done) {
@@ -246,21 +247,61 @@ void pat_init(void)
 		      PAT(4, WB) | PAT(5, WT) | PAT(6, UC_MINUS) | PAT(7, UC);
 		if (!boot_pat_state)
 			boot_pat_state = pat;
-	} else {
+
+	} else if ((c->x86_vendor == X86_VENDOR_INTEL) &&
+		   (((c->x86 == 0x6) && (c->x86_model <= 0xd)) ||
+		    ((c->x86 == 0xf) && (c->x86_model <= 0x6)))) {
 		/*
-		 * PTE encoding used in Linux:
+		 * PAT support with the lower four entries. Intel Pentium 2,
+		 * 3, M, and 4 are affected by PAT errata, which makes the
+		 * upper four entries unusable.  We do not use the upper four
+		 * entries for all the affected processor families for safe.
+		 *
+		 *  PTE encoding used in Linux:
 		 *      PAT
 		 *      |PCD
-		 *      ||PWT
-		 *      |||
-		 *      000 WB		_PAGE_CACHE_WB
-		 *      001 WC		_PAGE_CACHE_WC
-		 *      010 UC-		_PAGE_CACHE_UC_MINUS
-		 *      011 UC		_PAGE_CACHE_UC
+		 *      ||PWT  PAT
+		 *      |||    slot
+		 *      000    0    WB : _PAGE_CACHE_MODE_WB
+		 *      001    1    WC : _PAGE_CACHE_MODE_WC
+		 *      010    2    UC-: _PAGE_CACHE_MODE_UC_MINUS
+		 *      011    3    UC : _PAGE_CACHE_MODE_UC
 		 * PAT bit unused
+		 *
+		 * NOTE: When WT or WP is used, it is redirected to UC- per
+		 * the default setup in __cachemode2pte_tbl[].
 		 */
 		pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
 		      PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
+	} else {
+		/*
+		 * PAT full support.  We put WT in slot 7 to improve
+		 * robustness in the presence of errata that might cause
+		 * the high PAT bit to be ignored.  This way a buggy slot 7
+		 * access will hit slot 3, and slot 3 is UC, so at worst
+		 * we lose performance without causing a correctness issue.
+		 * Pentium 4 erratum N46 is an example of such an erratum,
+		 * although we try not to use PAT at all on affected CPUs.
+		 *
+		 *  PTE encoding used in Linux:
+		 *      PAT
+		 *      |PCD
+		 *      ||PWT  PAT
+		 *      |||    slot
+		 *      000    0    WB : _PAGE_CACHE_MODE_WB
+		 *      001    1    WC : _PAGE_CACHE_MODE_WC
+		 *      010    2    UC-: _PAGE_CACHE_MODE_UC_MINUS
+		 *      011    3    UC : _PAGE_CACHE_MODE_UC
+		 *      100    4    WB : Reserved
+		 *      101    5    WC : Reserved
+		 *      110    6    UC-: Reserved
+		 *      111    7    WT : _PAGE_CACHE_MODE_WT
+		 *
+		 * The reserved slots are unused, but mapped to their
+		 * corresponding types in the presence of PAT errata.
+		 */
+		pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
+		      PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, WT);
 	}
 
 	if (pat_enabled())

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[PATCH v11 4/12] x86, mm, pat: Change reserve_memtype() for WT

[Toshi Kani]

From: Toshi Kani <toshi.kani@hp.com>

When a RAM range is requested to reserve_memtype(), it calls
reserve_ram_pages_type() to verify the requested type.
reserve_ram_pages_type() is changed to fail WT and WP requests
with -EINVAL since set_page_memtype() is limited to handle
three types, WB, WC and UC-.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
---
Patch 10/12 enhances set_page_memtype() to support WT.
---
 arch/x86/mm/pat.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 3d9f125..85c9fcb 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -389,6 +389,8 @@ static int pat_pagerange_is_ram(resource_size_t start, resource_size_t end)
 
 /*
  * For RAM pages, we use page flags to mark the pages with appropriate type.
+ * The page flags are limited to three types, WB, WC and UC-.
+ * WT and WP requests fail with -EINVAL, and UC gets redirected to UC-.
  * Here we do two pass:
  * - Find the memtype of all the pages in the range, look for any conflicts
  * - In case of no conflicts, set the new memtype for pages in the range
@@ -400,6 +402,13 @@ static int reserve_ram_pages_type(u64 start, u64 end,
 	struct page *page;
 	u64 pfn;
 
+	if ((req_type == _PAGE_CACHE_MODE_WT) ||
+	    (req_type == _PAGE_CACHE_MODE_WP)) {
+		if (new_type)
+			*new_type = _PAGE_CACHE_MODE_UC_MINUS;
+		return -EINVAL;
+	}
+
 	if (req_type == _PAGE_CACHE_MODE_UC) {
 		/* We do not support strong UC */
 		WARN_ON_ONCE(1);
@@ -449,6 +458,7 @@ static int free_ram_pages_type(u64 start, u64 end)
  * - _PAGE_CACHE_MODE_WC
  * - _PAGE_CACHE_MODE_UC_MINUS
  * - _PAGE_CACHE_MODE_UC
+ * - _PAGE_CACHE_MODE_WT
  *
  * If new_type is NULL, function will return an error if it cannot reserve the
  * region with req_type. If new_type is non-NULL, function will return

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[PATCH v11 5/12] x86, asm: Change is_new_memtype_allowed() for WT

[Toshi Kani]

From: Toshi Kani <toshi.kani@hp.com>

__ioremap_caller() calls reserve_memtype() to set new_pcm
(existing map type if any), and then calls
is_new_memtype_allowed() to verify if converting to new_pcm
is allowed when pcm (request type) is different from new_pcm.

When WT is requested, the caller expects that writes are
ordered and uncached.  Therefore, this patch changes
is_new_memtype_allowed() to disallow the following cases.

 - If the request is WT, mapping type cannot be WB
 - If the request is WT, mapping type cannot be WC

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/include/asm/pgtable.h |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index fe57e7a..2562e30 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -398,11 +398,17 @@ static inline int is_new_memtype_allowed(u64 paddr, unsigned long size,
 	 * requested memtype:
 	 * - request is uncached, return cannot be write-back
 	 * - request is write-combine, return cannot be write-back
+	 * - request is write-through, return cannot be write-back
+	 * - request is write-through, return cannot be write-combine
 	 */
 	if ((pcm == _PAGE_CACHE_MODE_UC_MINUS &&
 	     new_pcm == _PAGE_CACHE_MODE_WB) ||
 	    (pcm == _PAGE_CACHE_MODE_WC &&
-	     new_pcm == _PAGE_CACHE_MODE_WB)) {
+	     new_pcm == _PAGE_CACHE_MODE_WB) ||
+	    (pcm == _PAGE_CACHE_MODE_WT &&
+	     new_pcm == _PAGE_CACHE_MODE_WB) ||
+	    (pcm == _PAGE_CACHE_MODE_WT &&
+	     new_pcm == _PAGE_CACHE_MODE_WC)) {
 		return 0;
 	}
 

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[PATCH v11 6/12] x86, mm, asm-gen: Add ioremap_wt() for WT

[Toshi Kani]

From: Toshi Kani <toshi.kani@hp.com>

This patch adds ioremap_wt() for creating WT mapping on x86.
It follows the same model as ioremap_wc() for multi-architecture
support.  ARCH_HAS_IOREMAP_WT is defined in the x86 version of
io.h to indicate that ioremap_wt() is implemented on x86.

Also update the PAT documentation file to cover ioremap_wt().

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
---
 Documentation/x86/pat.txt   |    4 +++-
 arch/x86/include/asm/io.h   |    2 ++
 arch/x86/mm/ioremap.c       |   21 +++++++++++++++++++++
 include/asm-generic/io.h    |    9 +++++++++
 include/asm-generic/iomap.h |    4 ++++
 5 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/Documentation/x86/pat.txt b/Documentation/x86/pat.txt
index 521bd8a..db0de6c 100644
--- a/Documentation/x86/pat.txt
+++ b/Documentation/x86/pat.txt
@@ -12,7 +12,7 @@ virtual addresses.
 
 PAT allows for different types of memory attributes. The most commonly used
 ones that will be supported at this time are Write-back, Uncached,
-Write-combined and Uncached Minus.
+Write-combined, Write-through and Uncached Minus.
 
 
 PAT APIs
@@ -40,6 +40,8 @@ ioremap_nocache        |    --    |    UC-     |       UC-        |
                        |          |            |                  |
 ioremap_wc             |    --    |    --      |       WC         |
                        |          |            |                  |
+ioremap_wt             |    --    |    --      |       WT         |
+                       |          |            |                  |
 set_memory_uc          |    UC-   |    --      |       --         |
  set_memory_wb         |          |            |                  |
                        |          |            |                  |
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index a2b9740..6c3a130 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -35,6 +35,7 @@
   */
 
 #define ARCH_HAS_IOREMAP_WC
+#define ARCH_HAS_IOREMAP_WT
 
 #include <linux/string.h>
 #include <linux/compiler.h>
@@ -321,6 +322,7 @@ extern void unxlate_dev_mem_ptr(phys_addr_t phys, void *addr);
 extern int ioremap_change_attr(unsigned long vaddr, unsigned long size,
 				enum page_cache_mode pcm);
 extern void __iomem *ioremap_wc(resource_size_t offset, unsigned long size);
+extern void __iomem *ioremap_wt(resource_size_t offset, unsigned long size);
 
 extern bool is_early_ioremap_ptep(pte_t *ptep);
 
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 078c270..779b1a2 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -172,6 +172,10 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
 		prot = __pgprot(pgprot_val(prot) |
 				cachemode2protval(_PAGE_CACHE_MODE_WC));
 		break;
+	case _PAGE_CACHE_MODE_WT:
+		prot = __pgprot(pgprot_val(prot) |
+				cachemode2protval(_PAGE_CACHE_MODE_WT));
+		break;
 	case _PAGE_CACHE_MODE_WB:
 		break;
 	}
@@ -297,6 +301,23 @@ void __iomem *ioremap_wc(resource_size_t phys_addr, unsigned long size)
 }
 EXPORT_SYMBOL(ioremap_wc);
 
+/**
+ * ioremap_wt	-	map memory into CPU space write through
+ * @phys_addr:	bus address of the memory
+ * @size:	size of the resource to map
+ *
+ * This version of ioremap ensures that the memory is marked write through.
+ * Write through stores data into memory while keeping the cache up-to-date.
+ *
+ * Must be freed with iounmap.
+ */
+void __iomem *ioremap_wt(resource_size_t phys_addr, unsigned long size)
+{
+	return __ioremap_caller(phys_addr, size, _PAGE_CACHE_MODE_WT,
+					__builtin_return_address(0));
+}
+EXPORT_SYMBOL(ioremap_wt);
+
 void __iomem *ioremap_cache(resource_size_t phys_addr, unsigned long size)
 {
 	return __ioremap_caller(phys_addr, size, _PAGE_CACHE_MODE_WB,
diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index 90ccba7..f56094c 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -785,8 +785,17 @@ static inline void __iomem *ioremap_wc(phys_addr_t offset, size_t size)
 }
 #endif
 
+#ifndef ioremap_wt
+#define ioremap_wt ioremap_wt
+static inline void __iomem *ioremap_wt(phys_addr_t offset, size_t size)
+{
+	return ioremap_nocache(offset, size);
+}
+#endif
+
 #ifndef iounmap
 #define iounmap iounmap
+
 static inline void iounmap(void __iomem *addr)
 {
 }
diff --git a/include/asm-generic/iomap.h b/include/asm-generic/iomap.h
index 1b41011..d8f8622 100644
--- a/include/asm-generic/iomap.h
+++ b/include/asm-generic/iomap.h
@@ -66,6 +66,10 @@ extern void ioport_unmap(void __iomem *);
 #define ioremap_wc ioremap_nocache
 #endif
 
+#ifndef ARCH_HAS_IOREMAP_WT
+#define ioremap_wt ioremap_nocache
+#endif
+
 #ifdef CONFIG_PCI
 /* Destroy a virtual mapping cookie for a PCI BAR (memory or IO) */
 struct pci_dev;

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[PATCH v11 7/12] arch/*/asm/io.h: Add ioremap_wt() to all architectures

[Toshi Kani]

From: Toshi Kani <toshi.kani@hp.com>

This patch adds ioremap_wt() to all arch-specific asm/io.h which
define ioremap_wc() locally.  These arch-specific asm/io.h do not
include <asm-generic/iomap.h>.  Some of them include
<asm-generic/io.h>, but ioremap_wt() is defined for consistency
since they define all ioremap_xxx locally.

ioremap_wt() is defined indentical to ioremap_nocache() to all
architectures without WT support.

frv and m68k already have ioremap_writethrough().  This patch
implements ioremap_wt() indetical to ioremap_writethrough() and
defines ARCH_HAS_IOREMAP_WT in both architectures.

This patch allows generic drivers to use ioremap_wt().

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
 arch/arc/include/asm/io.h        |    1 +
 arch/arm/include/asm/io.h        |    1 +
 arch/arm64/include/asm/io.h      |    1 +
 arch/avr32/include/asm/io.h      |    1 +
 arch/frv/include/asm/io.h        |    7 +++++++
 arch/m32r/include/asm/io.h       |    1 +
 arch/m68k/include/asm/io_mm.h    |    7 +++++++
 arch/m68k/include/asm/io_no.h    |    6 ++++++
 arch/metag/include/asm/io.h      |    3 +++
 arch/microblaze/include/asm/io.h |    1 +
 arch/mn10300/include/asm/io.h    |    1 +
 arch/nios2/include/asm/io.h      |    1 +
 arch/s390/include/asm/io.h       |    1 +
 arch/sparc/include/asm/io_32.h   |    1 +
 arch/sparc/include/asm/io_64.h   |    1 +
 arch/tile/include/asm/io.h       |    1 +
 arch/xtensa/include/asm/io.h     |    1 +
 17 files changed, 36 insertions(+)

diff --git a/arch/arc/include/asm/io.h b/arch/arc/include/asm/io.h
index cabd518..7cc4ced 100644
--- a/arch/arc/include/asm/io.h
+++ b/arch/arc/include/asm/io.h
@@ -20,6 +20,7 @@ extern void iounmap(const void __iomem *addr);
 
 #define ioremap_nocache(phy, sz)	ioremap(phy, sz)
 #define ioremap_wc(phy, sz)		ioremap(phy, sz)
+#define ioremap_wt(phy, sz)		ioremap(phy, sz)
 
 /* Change struct page to physical address */
 #define page_to_phys(page)		(page_to_pfn(page) << PAGE_SHIFT)
diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h
index db58deb..1b7677d 100644
--- a/arch/arm/include/asm/io.h
+++ b/arch/arm/include/asm/io.h
@@ -336,6 +336,7 @@ extern void _memset_io(volatile void __iomem *, int, size_t);
 #define ioremap_nocache(cookie,size)	__arm_ioremap((cookie), (size), MT_DEVICE)
 #define ioremap_cache(cookie,size)	__arm_ioremap((cookie), (size), MT_DEVICE_CACHED)
 #define ioremap_wc(cookie,size)		__arm_ioremap((cookie), (size), MT_DEVICE_WC)
+#define ioremap_wt(cookie,size)		__arm_ioremap((cookie), (size), MT_DEVICE)
 #define iounmap				__arm_iounmap
 
 /*
diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
index 540f7c0..7116d39 100644
--- a/arch/arm64/include/asm/io.h
+++ b/arch/arm64/include/asm/io.h
@@ -170,6 +170,7 @@ extern void __iomem *ioremap_cache(phys_addr_t phys_addr, size_t size);
 #define ioremap(addr, size)		__ioremap((addr), (size), __pgprot(PROT_DEVICE_nGnRE))
 #define ioremap_nocache(addr, size)	__ioremap((addr), (size), __pgprot(PROT_DEVICE_nGnRE))
 #define ioremap_wc(addr, size)		__ioremap((addr), (size), __pgprot(PROT_NORMAL_NC))
+#define ioremap_wt(addr, size)		__ioremap((addr), (size), __pgprot(PROT_DEVICE_nGnRE))
 #define iounmap				__iounmap
 
 /*
diff --git a/arch/avr32/include/asm/io.h b/arch/avr32/include/asm/io.h
index 4f5ec2b..e998ff5 100644
--- a/arch/avr32/include/asm/io.h
+++ b/arch/avr32/include/asm/io.h
@@ -296,6 +296,7 @@ extern void __iounmap(void __iomem *addr);
 	__iounmap(addr)
 
 #define ioremap_wc ioremap_nocache
+#define ioremap_wt ioremap_nocache
 
 #define cached(addr) P1SEGADDR(addr)
 #define uncached(addr) P2SEGADDR(addr)
diff --git a/arch/frv/include/asm/io.h b/arch/frv/include/asm/io.h
index 0b78bc8..1fe98fe 100644
--- a/arch/frv/include/asm/io.h
+++ b/arch/frv/include/asm/io.h
@@ -17,6 +17,8 @@
 
 #ifdef __KERNEL__
 
+#define ARCH_HAS_IOREMAP_WT
+
 #include <linux/types.h>
 #include <asm/virtconvert.h>
 #include <asm/string.h>
@@ -270,6 +272,11 @@ static inline void __iomem *ioremap_writethrough(unsigned long physaddr, unsigne
 	return __ioremap(physaddr, size, IOMAP_WRITETHROUGH);
 }
 
+static inline void __iomem *ioremap_wt(unsigned long physaddr, unsigned long size)
+{
+	return __ioremap(physaddr, size, IOMAP_WRITETHROUGH);
+}
+
 static inline void __iomem *ioremap_fullcache(unsigned long physaddr, unsigned long size)
 {
 	return __ioremap(physaddr, size, IOMAP_FULL_CACHING);
diff --git a/arch/m32r/include/asm/io.h b/arch/m32r/include/asm/io.h
index 9cc00db..0c3f25e 100644
--- a/arch/m32r/include/asm/io.h
+++ b/arch/m32r/include/asm/io.h
@@ -68,6 +68,7 @@ static inline void __iomem *ioremap(unsigned long offset, unsigned long size)
 extern void iounmap(volatile void __iomem *addr);
 #define ioremap_nocache(off,size) ioremap(off,size)
 #define ioremap_wc ioremap_nocache
+#define ioremap_wt ioremap_nocache
 
 /*
  * IO bus memory addresses are also 1:1 with the physical address
diff --git a/arch/m68k/include/asm/io_mm.h b/arch/m68k/include/asm/io_mm.h
index 8955b40..7c12138 100644
--- a/arch/m68k/include/asm/io_mm.h
+++ b/arch/m68k/include/asm/io_mm.h
@@ -20,6 +20,8 @@
 
 #ifdef __KERNEL__
 
+#define ARCH_HAS_IOREMAP_WT
+
 #include <linux/compiler.h>
 #include <asm/raw_io.h>
 #include <asm/virtconvert.h>
@@ -470,6 +472,11 @@ static inline void __iomem *ioremap_writethrough(unsigned long physaddr,
 {
 	return __ioremap(physaddr, size, IOMAP_WRITETHROUGH);
 }
+static inline void __iomem *ioremap_wt(unsigned long physaddr,
+					 unsigned long size)
+{
+	return __ioremap(physaddr, size, IOMAP_WRITETHROUGH);
+}
 static inline void __iomem *ioremap_fullcache(unsigned long physaddr,
 				      unsigned long size)
 {
diff --git a/arch/m68k/include/asm/io_no.h b/arch/m68k/include/asm/io_no.h
index a93c8cd..5fff9a2 100644
--- a/arch/m68k/include/asm/io_no.h
+++ b/arch/m68k/include/asm/io_no.h
@@ -3,6 +3,8 @@
 
 #ifdef __KERNEL__
 
+#define ARCH_HAS_IOREMAP_WT
+
 #include <asm/virtconvert.h>
 #include <asm-generic/iomap.h>
 
@@ -157,6 +159,10 @@ static inline void *ioremap_writethrough(unsigned long physaddr, unsigned long s
 {
 	return __ioremap(physaddr, size, IOMAP_WRITETHROUGH);
 }
+static inline void *ioremap_wt(unsigned long physaddr, unsigned long size)
+{
+	return __ioremap(physaddr, size, IOMAP_WRITETHROUGH);
+}
 static inline void *ioremap_fullcache(unsigned long physaddr, unsigned long size)
 {
 	return __ioremap(physaddr, size, IOMAP_FULL_CACHING);
diff --git a/arch/metag/include/asm/io.h b/arch/metag/include/asm/io.h
index d5779b0..9890f21 100644
--- a/arch/metag/include/asm/io.h
+++ b/arch/metag/include/asm/io.h
@@ -160,6 +160,9 @@ extern void __iounmap(void __iomem *addr);
 #define ioremap_wc(offset, size)                \
 	__ioremap((offset), (size), _PAGE_WR_COMBINE)
 
+#define ioremap_wt(offset, size)                \
+	__ioremap((offset), (size), 0)
+
 #define iounmap(addr)                           \
 	__iounmap(addr)
 
diff --git a/arch/microblaze/include/asm/io.h b/arch/microblaze/include/asm/io.h
index 940f5fc..ec3da11 100644
--- a/arch/microblaze/include/asm/io.h
+++ b/arch/microblaze/include/asm/io.h
@@ -43,6 +43,7 @@ extern void __iomem *ioremap(phys_addr_t address, unsigned long size);
 #define ioremap_nocache(addr, size)		ioremap((addr), (size))
 #define ioremap_fullcache(addr, size)		ioremap((addr), (size))
 #define ioremap_wc(addr, size)			ioremap((addr), (size))
+#define ioremap_wt(addr, size)			ioremap((addr), (size))
 
 #endif /* CONFIG_MMU */
 
diff --git a/arch/mn10300/include/asm/io.h b/arch/mn10300/include/asm/io.h
index cc4a2ba..07c5b4a 100644
--- a/arch/mn10300/include/asm/io.h
+++ b/arch/mn10300/include/asm/io.h
@@ -282,6 +282,7 @@ static inline void __iomem *ioremap_nocache(unsigned long offset, unsigned long
 }
 
 #define ioremap_wc ioremap_nocache
+#define ioremap_wt ioremap_nocache
 
 static inline void iounmap(void __iomem *addr)
 {
diff --git a/arch/nios2/include/asm/io.h b/arch/nios2/include/asm/io.h
index 6e24d7c..c5a62da 100644
--- a/arch/nios2/include/asm/io.h
+++ b/arch/nios2/include/asm/io.h
@@ -46,6 +46,7 @@ static inline void iounmap(void __iomem *addr)
 }
 
 #define ioremap_wc ioremap_nocache
+#define ioremap_wt ioremap_nocache
 
 /* Pages to physical address... */
 #define page_to_phys(page)	virt_to_phys(page_to_virt(page))
diff --git a/arch/s390/include/asm/io.h b/arch/s390/include/asm/io.h
index 30fd5c8..cb5fdf3 100644
--- a/arch/s390/include/asm/io.h
+++ b/arch/s390/include/asm/io.h
@@ -29,6 +29,7 @@ void unxlate_dev_mem_ptr(phys_addr_t phys, void *addr);
 
 #define ioremap_nocache(addr, size)	ioremap(addr, size)
 #define ioremap_wc			ioremap_nocache
+#define ioremap_wt			ioremap_nocache
 
 static inline void __iomem *ioremap(unsigned long offset, unsigned long size)
 {
diff --git a/arch/sparc/include/asm/io_32.h b/arch/sparc/include/asm/io_32.h
index 407ac14..57f26c3 100644
--- a/arch/sparc/include/asm/io_32.h
+++ b/arch/sparc/include/asm/io_32.h
@@ -129,6 +129,7 @@ static inline void sbus_memcpy_toio(volatile void __iomem *dst,
 void __iomem *ioremap(unsigned long offset, unsigned long size);
 #define ioremap_nocache(X,Y)	ioremap((X),(Y))
 #define ioremap_wc(X,Y)		ioremap((X),(Y))
+#define ioremap_wt(X,Y)		ioremap((X),(Y))
 void iounmap(volatile void __iomem *addr);
 
 /* Create a virtual mapping cookie for an IO port range */
diff --git a/arch/sparc/include/asm/io_64.h b/arch/sparc/include/asm/io_64.h
index 50d4840..c32fa3f 100644
--- a/arch/sparc/include/asm/io_64.h
+++ b/arch/sparc/include/asm/io_64.h
@@ -402,6 +402,7 @@ static inline void __iomem *ioremap(unsigned long offset, unsigned long size)
 
 #define ioremap_nocache(X,Y)		ioremap((X),(Y))
 #define ioremap_wc(X,Y)			ioremap((X),(Y))
+#define ioremap_wt(X,Y)			ioremap((X),(Y))
 
 static inline void iounmap(volatile void __iomem *addr)
 {
diff --git a/arch/tile/include/asm/io.h b/arch/tile/include/asm/io.h
index 6ef4eca..9c3d950 100644
--- a/arch/tile/include/asm/io.h
+++ b/arch/tile/include/asm/io.h
@@ -54,6 +54,7 @@ extern void iounmap(volatile void __iomem *addr);
 
 #define ioremap_nocache(physaddr, size)		ioremap(physaddr, size)
 #define ioremap_wc(physaddr, size)		ioremap(physaddr, size)
+#define ioremap_wt(physaddr, size)		ioremap(physaddr, size)
 #define ioremap_writethrough(physaddr, size)	ioremap(physaddr, size)
 #define ioremap_fullcache(physaddr, size)	ioremap(physaddr, size)
 
diff --git a/arch/xtensa/include/asm/io.h b/arch/xtensa/include/asm/io.h
index fe1600a..c39bb6e 100644
--- a/arch/xtensa/include/asm/io.h
+++ b/arch/xtensa/include/asm/io.h
@@ -59,6 +59,7 @@ static inline void __iomem *ioremap_cache(unsigned long offset,
 }
 
 #define ioremap_wc ioremap_nocache
+#define ioremap_wt ioremap_nocache
 
 static inline void __iomem *ioremap(unsigned long offset, unsigned long size)
 {

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[PATCH v11 8/12] video/fbdev, asm/io.h: Remove ioremap_writethrough()

[Toshi Kani]

From: Toshi Kani <toshi.kani@hp.com>

This patch removes the callers of ioremap_writethrough() by
replacing them with ioremap_wt() in three drivers under
drivers/video/fbdev.  It then removes ioremap_writethrough()
defined in some architecture's asm/io.h, frv, m68k, microblaze,
and tile.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
 arch/frv/include/asm/io.h        |    5 -----
 arch/m68k/include/asm/io_mm.h    |    5 -----
 arch/m68k/include/asm/io_no.h    |    4 ----
 arch/microblaze/include/asm/io.h |    1 -
 arch/tile/include/asm/io.h       |    1 -
 drivers/video/fbdev/amifb.c      |    4 ++--
 drivers/video/fbdev/atafb.c      |    3 +--
 drivers/video/fbdev/hpfb.c       |    4 ++--
 8 files changed, 5 insertions(+), 22 deletions(-)

diff --git a/arch/frv/include/asm/io.h b/arch/frv/include/asm/io.h
index 1fe98fe..a31b63e 100644
--- a/arch/frv/include/asm/io.h
+++ b/arch/frv/include/asm/io.h
@@ -267,11 +267,6 @@ static inline void __iomem *ioremap_nocache(unsigned long physaddr, unsigned lon
 	return __ioremap(physaddr, size, IOMAP_NOCACHE_SER);
 }
 
-static inline void __iomem *ioremap_writethrough(unsigned long physaddr, unsigned long size)
-{
-	return __ioremap(physaddr, size, IOMAP_WRITETHROUGH);
-}
-
 static inline void __iomem *ioremap_wt(unsigned long physaddr, unsigned long size)
 {
 	return __ioremap(physaddr, size, IOMAP_WRITETHROUGH);
diff --git a/arch/m68k/include/asm/io_mm.h b/arch/m68k/include/asm/io_mm.h
index 7c12138..618c85d3 100644
--- a/arch/m68k/include/asm/io_mm.h
+++ b/arch/m68k/include/asm/io_mm.h
@@ -467,11 +467,6 @@ static inline void __iomem *ioremap_nocache(unsigned long physaddr, unsigned lon
 {
 	return __ioremap(physaddr, size, IOMAP_NOCACHE_SER);
 }
-static inline void __iomem *ioremap_writethrough(unsigned long physaddr,
-					 unsigned long size)
-{
-	return __ioremap(physaddr, size, IOMAP_WRITETHROUGH);
-}
 static inline void __iomem *ioremap_wt(unsigned long physaddr,
 					 unsigned long size)
 {
diff --git a/arch/m68k/include/asm/io_no.h b/arch/m68k/include/asm/io_no.h
index 5fff9a2..ad7bd40 100644
--- a/arch/m68k/include/asm/io_no.h
+++ b/arch/m68k/include/asm/io_no.h
@@ -155,10 +155,6 @@ static inline void *ioremap_nocache(unsigned long physaddr, unsigned long size)
 {
 	return __ioremap(physaddr, size, IOMAP_NOCACHE_SER);
 }
-static inline void *ioremap_writethrough(unsigned long physaddr, unsigned long size)
-{
-	return __ioremap(physaddr, size, IOMAP_WRITETHROUGH);
-}
 static inline void *ioremap_wt(unsigned long physaddr, unsigned long size)
 {
 	return __ioremap(physaddr, size, IOMAP_WRITETHROUGH);
diff --git a/arch/microblaze/include/asm/io.h b/arch/microblaze/include/asm/io.h
index ec3da11..39b6315 100644
--- a/arch/microblaze/include/asm/io.h
+++ b/arch/microblaze/include/asm/io.h
@@ -39,7 +39,6 @@ extern resource_size_t isa_mem_base;
 extern void iounmap(void __iomem *addr);
 
 extern void __iomem *ioremap(phys_addr_t address, unsigned long size);
-#define ioremap_writethrough(addr, size)	ioremap((addr), (size))
 #define ioremap_nocache(addr, size)		ioremap((addr), (size))
 #define ioremap_fullcache(addr, size)		ioremap((addr), (size))
 #define ioremap_wc(addr, size)			ioremap((addr), (size))
diff --git a/arch/tile/include/asm/io.h b/arch/tile/include/asm/io.h
index 9c3d950..dc61de1 100644
--- a/arch/tile/include/asm/io.h
+++ b/arch/tile/include/asm/io.h
@@ -55,7 +55,6 @@ extern void iounmap(volatile void __iomem *addr);
 #define ioremap_nocache(physaddr, size)		ioremap(physaddr, size)
 #define ioremap_wc(physaddr, size)		ioremap(physaddr, size)
 #define ioremap_wt(physaddr, size)		ioremap(physaddr, size)
-#define ioremap_writethrough(physaddr, size)	ioremap(physaddr, size)
 #define ioremap_fullcache(physaddr, size)	ioremap(physaddr, size)
 
 #define mmiowb()
diff --git a/drivers/video/fbdev/amifb.c b/drivers/video/fbdev/amifb.c
index 35f7900..ee3a703 100644
--- a/drivers/video/fbdev/amifb.c
+++ b/drivers/video/fbdev/amifb.c
@@ -3705,8 +3705,8 @@ default_chipset:
 	 * access the videomem with writethrough cache
 	 */
 	info->fix.smem_start = (u_long)ZTWO_PADDR(videomemory);
-	videomemory = (u_long)ioremap_writethrough(info->fix.smem_start,
-						   info->fix.smem_len);
+	videomemory = (u_long)ioremap_wt(info->fix.smem_start,
+					 info->fix.smem_len);
 	if (!videomemory) {
 		dev_warn(&pdev->dev,
 			 "Unable to map videomem cached writethrough\n");
diff --git a/drivers/video/fbdev/atafb.c b/drivers/video/fbdev/atafb.c
index cb9ee25..d6ce613 100644
--- a/drivers/video/fbdev/atafb.c
+++ b/drivers/video/fbdev/atafb.c
@@ -3185,8 +3185,7 @@ int __init atafb_init(void)
 		/* Map the video memory (physical address given) to somewhere
 		 * in the kernel address space.
 		 */
-		external_screen_base = ioremap_writethrough(external_addr,
-						     external_len);
+		external_screen_base = ioremap_wt(external_addr, external_len);
 		if (external_vgaiobase)
 			external_vgaiobase =
 			  (unsigned long)ioremap(external_vgaiobase, 0x10000);
diff --git a/drivers/video/fbdev/hpfb.c b/drivers/video/fbdev/hpfb.c
index a1b7e5f..9476d19 100644
--- a/drivers/video/fbdev/hpfb.c
+++ b/drivers/video/fbdev/hpfb.c
@@ -241,8 +241,8 @@ static int hpfb_init_one(unsigned long phys_base, unsigned long virt_base)
 	fb_info.fix.line_length = fb_width;
 	fb_height = (in_8(fb_regs + HPFB_FBHMSB) << 8) | in_8(fb_regs + HPFB_FBHLSB);
 	fb_info.fix.smem_len = fb_width * fb_height;
-	fb_start = (unsigned long)ioremap_writethrough(fb_info.fix.smem_start,
-						       fb_info.fix.smem_len);
+	fb_start = (unsigned long)ioremap_wt(fb_info.fix.smem_start,
+					     fb_info.fix.smem_len);
 	hpfb_defined.xres = (in_8(fb_regs + HPFB_DWMSB) << 8) | in_8(fb_regs + HPFB_DWLSB);
 	hpfb_defined.yres = (in_8(fb_regs + HPFB_DHMSB) << 8) | in_8(fb_regs + HPFB_DHLSB);
 	hpfb_defined.xres_virtual = hpfb_defined.xres;

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[PATCH v11 9/12] x86, mm, pat: Add pgprot_writethrough() for WT

[Toshi Kani]

From: Toshi Kani <toshi.kani@hp.com>

This patch adds pgprot_writethrough() for setting WT to a given
pgprot_t.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/include/asm/pgtable_types.h |    3 +++
 arch/x86/mm/pat.c                    |    7 +++++++
 include/asm-generic/pgtable.h        |    4 ++++
 3 files changed, 14 insertions(+)

diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 78f0c8c..13f310b 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -367,6 +367,9 @@ extern int nx_enabled;
 #define pgprot_writecombine	pgprot_writecombine
 extern pgprot_t pgprot_writecombine(pgprot_t prot);
 
+#define pgprot_writethrough	pgprot_writethrough
+extern pgprot_t pgprot_writethrough(pgprot_t prot);
+
 /* Indicate that x86 has its own track and untrack pfn vma functions */
 #define __HAVE_PFNMAP_TRACKING
 
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 85c9fcb..1a2c84c 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -987,6 +987,13 @@ pgprot_t pgprot_writecombine(pgprot_t prot)
 }
 EXPORT_SYMBOL_GPL(pgprot_writecombine);
 
+pgprot_t pgprot_writethrough(pgprot_t prot)
+{
+	return __pgprot(pgprot_val(prot) |
+				cachemode2protval(_PAGE_CACHE_MODE_WT));
+}
+EXPORT_SYMBOL_GPL(pgprot_writethrough);
+
 #if defined(CONFIG_DEBUG_FS) && defined(CONFIG_X86_PAT)
 
 static struct memtype *memtype_get_idx(loff_t pos)
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 39f1d6a..bd910ce 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -262,6 +262,10 @@ static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
 #define pgprot_writecombine pgprot_noncached
 #endif
 
+#ifndef pgprot_writethrough
+#define pgprot_writethrough pgprot_noncached
+#endif
+
 #ifndef pgprot_device
 #define pgprot_device pgprot_noncached
 #endif

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[PATCH v11 10/12] x86, mm, asm: Add WT support to set_page_memtype()

[Toshi Kani]

From: Toshi Kani <toshi.kani@hp.com>

As set_memory_wb() calls free_ram_pages_type(), which then calls
set_page_memtype() with -1, _PGMT_DEFAULT is used for tracking
the WB type.  _PGMT_WB is defined but unused.  Hence, this patch
renames _PGMT_DEFAULT to _PGMT_WB to clarify the usage, and
releases the slot used by _PGMT_WB before.  free_ram_pages_type()
is changed to call set_page_memtype() with _PGMT_WB, and
get_page_memtype() returns _PAGE_CACHE_MODE_WB for _PGMT_WB.

This patch then defines _PGMT_WT to the released slot.  This enables
set_page_memtype() to track the WT type.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
 arch/x86/mm/pat.c |   60 +++++++++++++++++++++++++++--------------------------
 1 file changed, 30 insertions(+), 30 deletions(-)

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 1a2c84c..15d37c3 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -70,18 +70,22 @@ static u64 __read_mostly boot_pat_state;
 
 #ifdef CONFIG_X86_PAT
 /*
- * X86 PAT uses page flags WC and Uncached together to keep track of
- * memory type of pages that have backing page struct. X86 PAT supports 3
- * different memory types, _PAGE_CACHE_MODE_WB, _PAGE_CACHE_MODE_WC and
- * _PAGE_CACHE_MODE_UC_MINUS and fourth state where page's memory type has not
- * been changed from its default (value of -1 used to denote this).
- * Note we do not support _PAGE_CACHE_MODE_UC here.
+ * X86 PAT uses page flags arch_1 and uncached together to keep track of
+ * memory type of pages that have backing page struct.
+ *
+ * X86 PAT supports 4 different memory types:
+ *  - _PAGE_CACHE_MODE_WB
+ *  - _PAGE_CACHE_MODE_WC
+ *  - _PAGE_CACHE_MODE_UC_MINUS
+ *  - _PAGE_CACHE_MODE_WT
+ *
+ * _PAGE_CACHE_MODE_WB is the default type.
  */
 
-#define _PGMT_DEFAULT		0
+#define _PGMT_WB		0
 #define _PGMT_WC		(1UL << PG_arch_1)
 #define _PGMT_UC_MINUS		(1UL << PG_uncached)
-#define _PGMT_WB		(1UL << PG_uncached | 1UL << PG_arch_1)
+#define _PGMT_WT		(1UL << PG_uncached | 1UL << PG_arch_1)
 #define _PGMT_MASK		(1UL << PG_uncached | 1UL << PG_arch_1)
 #define _PGMT_CLEAR_MASK	(~_PGMT_MASK)
 
@@ -89,14 +93,14 @@ static inline enum page_cache_mode get_page_memtype(struct page *pg)
 {
 	unsigned long pg_flags = pg->flags & _PGMT_MASK;
 
-	if (pg_flags == _PGMT_DEFAULT)
-		return -1;
+	if (pg_flags == _PGMT_WB)
+		return _PAGE_CACHE_MODE_WB;
 	else if (pg_flags == _PGMT_WC)
 		return _PAGE_CACHE_MODE_WC;
 	else if (pg_flags == _PGMT_UC_MINUS)
 		return _PAGE_CACHE_MODE_UC_MINUS;
 	else
-		return _PAGE_CACHE_MODE_WB;
+		return _PAGE_CACHE_MODE_WT;
 }
 
 static inline void set_page_memtype(struct page *pg,
@@ -113,11 +117,12 @@ static inline void set_page_memtype(struct page *pg,
 	case _PAGE_CACHE_MODE_UC_MINUS:
 		memtype_flags = _PGMT_UC_MINUS;
 		break;
-	case _PAGE_CACHE_MODE_WB:
-		memtype_flags = _PGMT_WB;
+	case _PAGE_CACHE_MODE_WT:
+		memtype_flags = _PGMT_WT;
 		break;
+	case _PAGE_CACHE_MODE_WB:
 	default:
-		memtype_flags = _PGMT_DEFAULT;
+		memtype_flags = _PGMT_WB;
 		break;
 	}
 
@@ -389,8 +394,11 @@ static int pat_pagerange_is_ram(resource_size_t start, resource_size_t end)
 
 /*
  * For RAM pages, we use page flags to mark the pages with appropriate type.
- * The page flags are limited to three types, WB, WC and UC-.
- * WT and WP requests fail with -EINVAL, and UC gets redirected to UC-.
+ * The page flags are limited to four types, WB (default), WC, WT and UC-.
+ * WP request fails with -EINVAL, and UC gets redirected to UC-.  Setting
+ * a new memory type is only allowed to a page mapped with the default WB
+ * type.
+ *
  * Here we do two pass:
  * - Find the memtype of all the pages in the range, look for any conflicts
  * - In case of no conflicts, set the new memtype for pages in the range
@@ -402,8 +410,7 @@ static int reserve_ram_pages_type(u64 start, u64 end,
 	struct page *page;
 	u64 pfn;
 
-	if ((req_type == _PAGE_CACHE_MODE_WT) ||
-	    (req_type == _PAGE_CACHE_MODE_WP)) {
+	if (req_type == _PAGE_CACHE_MODE_WP) {
 		if (new_type)
 			*new_type = _PAGE_CACHE_MODE_UC_MINUS;
 		return -EINVAL;
@@ -420,7 +427,7 @@ static int reserve_ram_pages_type(u64 start, u64 end,
 
 		page = pfn_to_page(pfn);
 		type = get_page_memtype(page);
-		if (type != -1) {
+		if (type != _PAGE_CACHE_MODE_WB) {
 			pr_info("x86/PAT: reserve_ram_pages_type failed [mem %#010Lx-%#010Lx], track 0x%x, req 0x%x\n",
 				start, end - 1, type, req_type);
 			if (new_type)
@@ -447,7 +454,7 @@ static int free_ram_pages_type(u64 start, u64 end)
 
 	for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
 		page = pfn_to_page(pfn);
-		set_page_memtype(page, -1);
+		set_page_memtype(page, _PAGE_CACHE_MODE_WB);
 	}
 	return 0;
 }
@@ -588,7 +595,7 @@ int free_memtype(u64 start, u64 end)
  * Only to be called when PAT is enabled
  *
  * Returns _PAGE_CACHE_MODE_WB, _PAGE_CACHE_MODE_WC, _PAGE_CACHE_MODE_UC_MINUS
- * or _PAGE_CACHE_MODE_UC
+ * or _PAGE_CACHE_MODE_WT.
  */
 static enum page_cache_mode lookup_memtype(u64 paddr)
 {
@@ -600,16 +607,9 @@ static enum page_cache_mode lookup_memtype(u64 paddr)
 
 	if (pat_pagerange_is_ram(paddr, paddr + PAGE_SIZE)) {
 		struct page *page;
-		page = pfn_to_page(paddr >> PAGE_SHIFT);
-		rettype = get_page_memtype(page);
-		/*
-		 * -1 from get_page_memtype() implies RAM page is in its
-		 * default state and not reserved, and hence of type WB
-		 */
-		if (rettype == -1)
-			rettype = _PAGE_CACHE_MODE_WB;
 
-		return rettype;
+		page = pfn_to_page(paddr >> PAGE_SHIFT);
+		return get_page_memtype(page);
 	}
 
 	spin_lock(&memtype_lock);

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[PATCH v11 11/12] x86, mm: Add set_memory_wt() for WT

[Toshi Kani]

From: Toshi Kani <toshi.kani@hp.com>

Now that reserve_ram_pages_type() accepts the WT type, this
patch adds set_memory_wt(), set_memory_array_wt() and
set_pages_array_wt() for setting the WT type to the regular
memory.

ioremap_change_attr() is also extended to accept the WT type.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
 Documentation/x86/pat.txt         |    9 ++++-
 arch/x86/include/asm/cacheflush.h |    6 +++-
 arch/x86/mm/ioremap.c             |    3 ++
 arch/x86/mm/pageattr.c            |   62 +++++++++++++++++++++++++++++--------
 4 files changed, 63 insertions(+), 17 deletions(-)

diff --git a/Documentation/x86/pat.txt b/Documentation/x86/pat.txt
index db0de6c..54944c7 100644
--- a/Documentation/x86/pat.txt
+++ b/Documentation/x86/pat.txt
@@ -48,6 +48,9 @@ set_memory_uc          |    UC-   |    --      |       --         |
 set_memory_wc          |    WC    |    --      |       --         |
  set_memory_wb         |          |            |                  |
                        |          |            |                  |
+set_memory_wt          |    WT    |    --      |       --         |
+ set_memory_wb         |          |            |                  |
+                       |          |            |                  |
 pci sysfs resource     |    --    |    --      |       UC-        |
                        |          |            |                  |
 pci sysfs resource_wc  |    --    |    --      |       WC         |
@@ -150,8 +153,8 @@ can be more restrictive, in case of any existing aliasing for that address.
 For example: If there is an existing uncached mapping, a new ioremap_wc can
 return uncached mapping in place of write-combine requested.
 
-set_memory_[uc|wc] and set_memory_wb should be used in pairs, where driver will
-first make a region uc or wc and switch it back to wb after use.
+set_memory_[uc|wc|wt] and set_memory_wb should be used in pairs, where driver
+will first make a region uc, wc or wt and switch it back to wb after use.
 
 Over time writes to /proc/mtrr will be deprecated in favor of using PAT based
 interfaces. Users writing to /proc/mtrr are suggested to use above interfaces.
@@ -159,7 +162,7 @@ interfaces. Users writing to /proc/mtrr are suggested to use above interfaces.
 Drivers should use ioremap_[uc|wc] to access PCI BARs with [uc|wc] access
 types.
 
-Drivers should use set_memory_[uc|wc] to set access type for RAM ranges.
+Drivers should use set_memory_[uc|wc|wt] to set access type for RAM ranges.
 
 
 PAT debugging
diff --git a/arch/x86/include/asm/cacheflush.h b/arch/x86/include/asm/cacheflush.h
index 47c8e32..b6f7457 100644
--- a/arch/x86/include/asm/cacheflush.h
+++ b/arch/x86/include/asm/cacheflush.h
@@ -8,7 +8,7 @@
 /*
  * The set_memory_* API can be used to change various attributes of a virtual
  * address range. The attributes include:
- * Cachability   : UnCached, WriteCombining, WriteBack
+ * Cachability   : UnCached, WriteCombining, WriteThrough, WriteBack
  * Executability : eXeutable, NoteXecutable
  * Read/Write    : ReadOnly, ReadWrite
  * Presence      : NotPresent
@@ -35,9 +35,11 @@
 
 int _set_memory_uc(unsigned long addr, int numpages);
 int _set_memory_wc(unsigned long addr, int numpages);
+int _set_memory_wt(unsigned long addr, int numpages);
 int _set_memory_wb(unsigned long addr, int numpages);
 int set_memory_uc(unsigned long addr, int numpages);
 int set_memory_wc(unsigned long addr, int numpages);
+int set_memory_wt(unsigned long addr, int numpages);
 int set_memory_wb(unsigned long addr, int numpages);
 int set_memory_x(unsigned long addr, int numpages);
 int set_memory_nx(unsigned long addr, int numpages);
@@ -48,10 +50,12 @@ int set_memory_4k(unsigned long addr, int numpages);
 
 int set_memory_array_uc(unsigned long *addr, int addrinarray);
 int set_memory_array_wc(unsigned long *addr, int addrinarray);
+int set_memory_array_wt(unsigned long *addr, int addrinarray);
 int set_memory_array_wb(unsigned long *addr, int addrinarray);
 
 int set_pages_array_uc(struct page **pages, int addrinarray);
 int set_pages_array_wc(struct page **pages, int addrinarray);
+int set_pages_array_wt(struct page **pages, int addrinarray);
 int set_pages_array_wb(struct page **pages, int addrinarray);
 
 /*
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 779b1a2..cc5ccc4 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -42,6 +42,9 @@ int ioremap_change_attr(unsigned long vaddr, unsigned long size,
 	case _PAGE_CACHE_MODE_WC:
 		err = _set_memory_wc(vaddr, nrpages);
 		break;
+	case _PAGE_CACHE_MODE_WT:
+		err = _set_memory_wt(vaddr, nrpages);
+		break;
 	case _PAGE_CACHE_MODE_WB:
 		err = _set_memory_wb(vaddr, nrpages);
 		break;
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 94aae76..d908f19 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1502,12 +1502,10 @@ EXPORT_SYMBOL(set_memory_uc);
 static int _set_memory_array(unsigned long *addr, int addrinarray,
 		enum page_cache_mode new_type)
 {
+	enum page_cache_mode set_type;
 	int i, j;
 	int ret;
 
-	/*
-	 * for now UC MINUS. see comments in ioremap_nocache()
-	 */
 	for (i = 0; i < addrinarray; i++) {
 		ret = reserve_memtype(__pa(addr[i]), __pa(addr[i]) + PAGE_SIZE,
 					new_type, NULL);
@@ -1515,9 +1513,12 @@ static int _set_memory_array(unsigned long *addr, int addrinarray,
 			goto out_free;
 	}
 
+	/* If WC, set to UC- first and then WC */
+	set_type = (new_type == _PAGE_CACHE_MODE_WC) ?
+				_PAGE_CACHE_MODE_UC_MINUS : new_type;
+
 	ret = change_page_attr_set(addr, addrinarray,
-				   cachemode2pgprot(_PAGE_CACHE_MODE_UC_MINUS),
-				   1);
+				   cachemode2pgprot(set_type), 1);
 
 	if (!ret && new_type == _PAGE_CACHE_MODE_WC)
 		ret = change_page_attr_set_clr(addr, addrinarray,
@@ -1549,6 +1550,12 @@ int set_memory_array_wc(unsigned long *addr, int addrinarray)
 }
 EXPORT_SYMBOL(set_memory_array_wc);
 
+int set_memory_array_wt(unsigned long *addr, int addrinarray)
+{
+	return _set_memory_array(addr, addrinarray, _PAGE_CACHE_MODE_WT);
+}
+EXPORT_SYMBOL_GPL(set_memory_array_wt);
+
 int _set_memory_wc(unsigned long addr, int numpages)
 {
 	int ret;
@@ -1574,21 +1581,39 @@ int set_memory_wc(unsigned long addr, int numpages)
 	ret = reserve_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE,
 		_PAGE_CACHE_MODE_WC, NULL);
 	if (ret)
-		goto out_err;
+		return ret;
 
 	ret = _set_memory_wc(addr, numpages);
 	if (ret)
-		goto out_free;
+		free_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE);
 
-	return 0;
-
-out_free:
-	free_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE);
-out_err:
 	return ret;
 }
 EXPORT_SYMBOL(set_memory_wc);
 
+int _set_memory_wt(unsigned long addr, int numpages)
+{
+	return change_page_attr_set(&addr, numpages,
+				    cachemode2pgprot(_PAGE_CACHE_MODE_WT), 0);
+}
+
+int set_memory_wt(unsigned long addr, int numpages)
+{
+	int ret;
+
+	ret = reserve_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE,
+			      _PAGE_CACHE_MODE_WT, NULL);
+	if (ret)
+		return ret;
+
+	ret = _set_memory_wt(addr, numpages);
+	if (ret)
+		free_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(set_memory_wt);
+
 int _set_memory_wb(unsigned long addr, int numpages)
 {
 	/* WB cache mode is hard wired to all cache attribute bits being 0 */
@@ -1679,6 +1704,7 @@ static int _set_pages_array(struct page **pages, int addrinarray,
 {
 	unsigned long start;
 	unsigned long end;
+	enum page_cache_mode set_type;
 	int i;
 	int free_idx;
 	int ret;
@@ -1692,8 +1718,12 @@ static int _set_pages_array(struct page **pages, int addrinarray,
 			goto err_out;
 	}
 
+	/* If WC, set to UC- first and then WC */
+	set_type = (new_type == _PAGE_CACHE_MODE_WC) ?
+				_PAGE_CACHE_MODE_UC_MINUS : new_type;
+
 	ret = cpa_set_pages_array(pages, addrinarray,
-			cachemode2pgprot(_PAGE_CACHE_MODE_UC_MINUS));
+				  cachemode2pgprot(set_type));
 	if (!ret && new_type == _PAGE_CACHE_MODE_WC)
 		ret = change_page_attr_set_clr(NULL, addrinarray,
 					       cachemode2pgprot(
@@ -1727,6 +1757,12 @@ int set_pages_array_wc(struct page **pages, int addrinarray)
 }
 EXPORT_SYMBOL(set_pages_array_wc);
 
+int set_pages_array_wt(struct page **pages, int addrinarray)
+{
+	return _set_pages_array(pages, addrinarray, _PAGE_CACHE_MODE_WT);
+}
+EXPORT_SYMBOL_GPL(set_pages_array_wt);
+
 int set_pages_wb(struct page *page, int numpages)
 {
 	unsigned long addr = (unsigned long)page_address(page);

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[PATCH v11 12/12] drivers/block/pmem: Map NVDIMM with ioremap_wt()

[Toshi Kani]

From: Toshi Kani <toshi.kani@hp.com>

The pmem driver maps NVDIMM with ioremap_nocache() as we cannot
write back the contents of the CPU caches in case of a crash.

This patch changes to use ioremap_wt(), which provides uncached
writes but cached reads, for improving read performance.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
 drivers/block/pmem.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/pmem.c b/drivers/block/pmem.c
index eabf4a8..095dfaa 100644
--- a/drivers/block/pmem.c
+++ b/drivers/block/pmem.c
@@ -139,11 +139,11 @@ static struct pmem_device *pmem_alloc(struct device *dev, struct resource *res)
 	}
 
 	/*
-	 * Map the memory as non-cachable, as we can't write back the contents
+	 * Map the memory as write-through, as we can't write back the contents
 	 * of the CPU caches in case of a crash.
 	 */
 	err = -ENOMEM;
-	pmem->virt_addr = ioremap_nocache(pmem->phys_addr, pmem->size);
+	pmem->virt_addr = ioremap_wt(pmem->phys_addr, pmem->size);
 	if (!pmem->virt_addr)
 		goto out_release_region;
 

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Re: [PATCH v11 12/12] drivers/block/pmem: Map NVDIMM with ioremap_wt()

[Dan Williams]

On Fri, May 29, 2015 at 3:59 PM, Toshi Kani <toshi.kani@hp.com> wrote:
> From: Toshi Kani <toshi.kani@hp.com>
>
> The pmem driver maps NVDIMM with ioremap_nocache() as we cannot
> write back the contents of the CPU caches in case of a crash.
>
> This patch changes to use ioremap_wt(), which provides uncached
> writes but cached reads, for improving read performance.
>
> Signed-off-by: Toshi Kani <toshi.kani@hp.com>

Acked-by: Dan Williams <dan.j.williams@intel.com>

...with the caveat that I'm going to follow in behind this series with
generic ioremap_cache() enabling and converting pmem to use
persistent_copy() / persistent_sync() when the arch/cpu has persistent
memory synchronization instructions.  After the conversion
ioremap_wt() will still be there for the non-persistent_sync() capable
case.

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Re: [PATCH v11 6/12] x86, mm, asm-gen: Add ioremap_wt() for WT

[Geert Uytterhoeven]

On Sat, May 30, 2015 at 12:59 AM, Toshi Kani <toshi.kani@hp.com> wrote:
> --- a/include/asm-generic/io.h
> +++ b/include/asm-generic/io.h
> @@ -785,8 +785,17 @@ static inline void __iomem *ioremap_wc(phys_addr_t offset, size_t size)
>  }
>  #endif
>
> +#ifndef ioremap_wt
> +#define ioremap_wt ioremap_wt
> +static inline void __iomem *ioremap_wt(phys_addr_t offset, size_t size)
> +{
> +       return ioremap_nocache(offset, size);
> +}
> +#endif
> +
>  #ifndef iounmap
>  #define iounmap iounmap
> +
>  static inline void iounmap(void __iomem *addr)
>  {
>  }
> diff --git a/include/asm-generic/iomap.h b/include/asm-generic/iomap.h
> index 1b41011..d8f8622 100644
> --- a/include/asm-generic/iomap.h
> +++ b/include/asm-generic/iomap.h
> @@ -66,6 +66,10 @@ extern void ioport_unmap(void __iomem *);
>  #define ioremap_wc ioremap_nocache
>  #endif
>
> +#ifndef ARCH_HAS_IOREMAP_WT
> +#define ioremap_wt ioremap_nocache
> +#endif

Defining ioremap_wt in two different places in asm-generic looks fishy to me.

If <asm/io.h> already provides it (either through asm-generic/io.h or
arch/<arch>/include/asm/io.h), why does asm-generic/iomap.h need to define
its own version?

I see this pattern already exists for ioremap_wc...

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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Re: [PATCH v11 6/12] x86, mm, asm-gen: Add ioremap_wt() for WT

[Toshi Kani]

On Sat, 2015-05-30 at 11:18 +0200, Geert Uytterhoeven wrote:
> On Sat, May 30, 2015 at 12:59 AM, Toshi Kani <toshi.kani@hp.com> wrote:
> > --- a/include/asm-generic/io.h
> > +++ b/include/asm-generic/io.h
> > @@ -785,8 +785,17 @@ static inline void __iomem *ioremap_wc(phys_addr_t offset, size_t size)
> >  }
> >  #endif
> >
> > +#ifndef ioremap_wt
> > +#define ioremap_wt ioremap_wt
> > +static inline void __iomem *ioremap_wt(phys_addr_t offset, size_t size)
> > +{
> > +       return ioremap_nocache(offset, size);
> > +}
> > +#endif
> > +
> >  #ifndef iounmap
> >  #define iounmap iounmap
> > +
> >  static inline void iounmap(void __iomem *addr)
> >  {
> >  }
> > diff --git a/include/asm-generic/iomap.h b/include/asm-generic/iomap.h
> > index 1b41011..d8f8622 100644
> > --- a/include/asm-generic/iomap.h
> > +++ b/include/asm-generic/iomap.h
> > @@ -66,6 +66,10 @@ extern void ioport_unmap(void __iomem *);
> >  #define ioremap_wc ioremap_nocache
> >  #endif
> >
> > +#ifndef ARCH_HAS_IOREMAP_WT
> > +#define ioremap_wt ioremap_nocache
> > +#endif
> 
> Defining ioremap_wt in two different places in asm-generic looks fishy to me.
> 
> If <asm/io.h> already provides it (either through asm-generic/io.h or
> arch/<arch>/include/asm/io.h), why does asm-generic/iomap.h need to define
> its own version?
> 
> I see this pattern already exists for ioremap_wc...

Yes, this patchset follows the model of ioremap_wc.  This duplication
was introduced by 9216efafc52 "asm-generic/io.h: Reconcile I/O accessor
overrides", while the original ioremap_wc support changed
asm-generic/iomap.h (1526a756fba).  As described in patch 07, some
architectures define ioremap_xxx() locally as well.

It is too risky to do everything in one short.  I will look into the
duplication issue as a separate item after this patchset is settled.

Thanks,
-Toshi

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Re: [PATCH v11 2/12] x86, mm, pat: Refactor !pat_enabled handling

[Borislav Petkov]

On Fri, May 29, 2015 at 04:59:00PM -0600, Toshi Kani wrote:
> From: Toshi Kani <toshi.kani@hp.com>
> 
> This patch refactors the !pat_enabled code paths and integrates
> them into the PAT abstraction code.  The PAT table is emulated by
> corresponding to the two cache attribute bits, PWT (Write Through)
> and PCD (Cache Disable).  The emulated PAT table is the same as the
> BIOS default setup when the system has PAT but the "nopat" boot
> option is specified.  The emulated PAT table is also used when
> MSR_IA32_CR_PAT returns 0 -- 9d34cfdf4796 ("x86: Don't rely on
> VMWare emulating PAT MSR correctly").

To be honest, I wasn't surprised when you sent me the same patch and
ignored most of my comments. For the future, please let me know if I'm
wasting my time with commenting on your stuff so that I can plan my work
and not waste time and energy reviewing, ok?

Unfortunately, if you want something done right, you have to do it
yourself.

So I did that, I split that ugly cleanup into something much more
readable, patches as a reply to this message.

Feel free to base your work ontop of

git://git.kernel.org/pub/scm/linux/kernel/git/bp/bp.git#tip-mm-2

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--

[PATCH 1/4] x86/pat: Untangle pat_init()

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

Split it into a BSP and AP version which makes the PAT initialization
path actually readable again.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: arnd@arndb.de
Cc: Elliott@hp.com
Cc: hch@lst.de
Cc: hmh@hmh.eng.br
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: jgross@suse.com
Cc: konrad.wilk@oracle.com
Cc: linux-mm <linux-mm@kvack.org>
Cc: linux-nvdimm@lists.01.org
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: stefan.bader@canonical.com
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: x86-ml <x86@kernel.org>
Cc: yigal@plexistor.com
---
 arch/x86/mm/pat.c | 69 ++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 40 insertions(+), 29 deletions(-)

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index a1c96544099d..476d0780560f 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -36,6 +36,8 @@
 #undef pr_fmt
 #define pr_fmt(fmt) "" fmt
 
+static bool boot_cpu_done;
+
 static int __read_mostly __pat_enabled = IS_ENABLED(CONFIG_X86_PAT);
 
 static inline void pat_disable(const char *reason)
@@ -194,31 +196,47 @@ void pat_init_cache_modes(void)
 
 #define PAT(x, y)	((u64)PAT_ ## y << ((x)*8))
 
-void pat_init(void)
+static void pat_bsp_init(u64 pat)
 {
-	u64 pat;
-	bool boot_cpu = !boot_pat_state;
+	if (!cpu_has_pat) {
+		pat_disable("PAT not supported by CPU.");
+		return;
+	}
 
-	if (!pat_enabled())
+	rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
+	if (!boot_pat_state) {
+		pat_disable("PAT MSR is 0, disabled.");
 		return;
+	}
 
+	wrmsrl(MSR_IA32_CR_PAT, pat);
+
+	pat_init_cache_modes();
+}
+
+static void pat_ap_init(u64 pat)
+{
 	if (!cpu_has_pat) {
-		if (!boot_pat_state) {
-			pat_disable("PAT not supported by CPU.");
-			return;
-		} else {
-			/*
-			 * If this happens we are on a secondary CPU, but
-			 * switched to PAT on the boot CPU. We have no way to
-			 * undo PAT.
-			 */
-			pr_err("x86/PAT: PAT enabled, but not supported by secondary CPU\n");
-			BUG();
-		}
+		/*
+		 * If this happens we are on a secondary CPU, but switched to
+		 * PAT on the boot CPU. We have no way to undo PAT.
+		 */
+		panic("x86/PAT: PAT enabled, but not supported by secondary CPU\n");
 	}
 
-	/* Set PWT to Write-Combining. All other bits stay the same */
+	wrmsrl(MSR_IA32_CR_PAT, pat);
+}
+
+void pat_init(void)
+{
+	u64 pat;
+
+	if (!pat_enabled())
+		return;
+
 	/*
+	 * Set PWT to Write-Combining. All other bits stay the same:
+	 *
 	 * PTE encoding used in Linux:
 	 *      PAT
 	 *      |PCD
@@ -233,19 +251,12 @@ void pat_init(void)
 	pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
 	      PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
 
-	/* Boot CPU check */
-	if (!boot_pat_state) {
-		rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
-		if (!boot_pat_state) {
-			pat_disable("PAT read returns always zero, disabled.");
-			return;
-		}
+	if (!boot_cpu_done) {
+		pat_bsp_init(pat);
+		boot_cpu_done = true;
+	} else {
+		pat_ap_init(pat);
 	}
-
-	wrmsrl(MSR_IA32_CR_PAT, pat);
-
-	if (boot_cpu)
-		pat_init_cache_modes();
 }
 
 #undef PAT
-- 
2.3.5

[PATCH 2/4] x86/pat: Merge pat_init_cache_modes() into its caller

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

This way we can pass pat MSR value directly.

No functionality change.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: arnd@arndb.de
Cc: Elliott@hp.com
Cc: hch@lst.de
Cc: hmh@hmh.eng.br
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: jgross@suse.com
Cc: konrad.wilk@oracle.com
Cc: linux-mm <linux-mm@kvack.org>
Cc: linux-nvdimm@lists.01.org
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: stefan.bader@canonical.com
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: x86-ml <x86@kernel.org>
Cc: yigal@plexistor.com
---
 arch/x86/mm/pat.c | 39 ++++++++++++++++-----------------------
 1 file changed, 16 insertions(+), 23 deletions(-)

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 476d0780560f..4d28759f5a1a 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -172,32 +172,14 @@ static enum page_cache_mode pat_get_cache_mode(unsigned pat_val, char *msg)
 
 #undef CM
 
-/*
- * Update the cache mode to pgprot translation tables according to PAT
- * configuration.
- * Using lower indices is preferred, so we start with highest index.
- */
-void pat_init_cache_modes(void)
-{
-	int i;
-	enum page_cache_mode cache;
-	char pat_msg[33];
-	u64 pat;
-
-	rdmsrl(MSR_IA32_CR_PAT, pat);
-	pat_msg[32] = 0;
-	for (i = 7; i >= 0; i--) {
-		cache = pat_get_cache_mode((pat >> (i * 8)) & 7,
-					   pat_msg + 4 * i);
-		update_cache_mode_entry(i, cache);
-	}
-	pr_info("x86/PAT: Configuration [0-7]: %s\n", pat_msg);
-}
-
 #define PAT(x, y)	((u64)PAT_ ## y << ((x)*8))
 
 static void pat_bsp_init(u64 pat)
 {
+	enum page_cache_mode cache;
+	char pat_msg[33];
+	int i;
+
 	if (!cpu_has_pat) {
 		pat_disable("PAT not supported by CPU.");
 		return;
@@ -211,7 +193,18 @@ static void pat_bsp_init(u64 pat)
 
 	wrmsrl(MSR_IA32_CR_PAT, pat);
 
-	pat_init_cache_modes();
+	pat_msg[32] = 0;
+
+	/*
+	 * Update the cache mode to pgprot translation tables according to PAT
+	 * configuration. Using lower indices is preferred, so we start with
+	 * highest index.
+	 */
+	for (i = 7; i >= 0; i--) {
+		cache = pat_get_cache_mode((pat >> (i * 8)) & 7, pat_msg + 4 * i);
+		update_cache_mode_entry(i, cache);
+	}
+	pr_info("x86/PAT: Configuration [0-7]: %s\n", pat_msg);
 }
 
 static void pat_ap_init(u64 pat)
-- 
2.3.5

[PATCH 3/4] x86/pat: Emulate PAT when it is disabled

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

In the case when PAT is disabled on the command line with "nopat" or
when virtualization doesn't support PAT (correctly) - see

  9d34cfdf4796 ("x86: Don't rely on VMWare emulating PAT MSR correctly").

we emulate it using the PWT and PCD cache attribute bits. Get rid of
boot_pat_state while at it.

Based on a conglomerate patch from Toshi Kani.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: arnd@arndb.de
Cc: Elliott@hp.com
Cc: hch@lst.de
Cc: hmh@hmh.eng.br
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: jgross@suse.com
Cc: konrad.wilk@oracle.com
Cc: linux-mm <linux-mm@kvack.org>
Cc: linux-nvdimm@lists.01.org
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: stefan.bader@canonical.com
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: x86-ml <x86@kernel.org>
Cc: yigal@plexistor.com
---
 arch/x86/mm/init.c |  6 ++---
 arch/x86/mm/pat.c  | 72 +++++++++++++++++++++++++++++++++++++-----------------
 2 files changed, 52 insertions(+), 26 deletions(-)

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 1d553186c434..8533b46e6bee 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -40,7 +40,7 @@
  */
 uint16_t __cachemode2pte_tbl[_PAGE_CACHE_MODE_NUM] = {
 	[_PAGE_CACHE_MODE_WB      ]	= 0         | 0        ,
-	[_PAGE_CACHE_MODE_WC      ]	= _PAGE_PWT | 0        ,
+	[_PAGE_CACHE_MODE_WC      ]	= 0         | _PAGE_PCD,
 	[_PAGE_CACHE_MODE_UC_MINUS]	= 0         | _PAGE_PCD,
 	[_PAGE_CACHE_MODE_UC      ]	= _PAGE_PWT | _PAGE_PCD,
 	[_PAGE_CACHE_MODE_WT      ]	= 0         | _PAGE_PCD,
@@ -50,11 +50,11 @@ EXPORT_SYMBOL(__cachemode2pte_tbl);
 
 uint8_t __pte2cachemode_tbl[8] = {
 	[__pte2cm_idx( 0        | 0         | 0        )] = _PAGE_CACHE_MODE_WB,
-	[__pte2cm_idx(_PAGE_PWT | 0         | 0        )] = _PAGE_CACHE_MODE_WC,
+	[__pte2cm_idx(_PAGE_PWT | 0         | 0        )] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx( 0        | _PAGE_PCD | 0        )] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | 0        )] = _PAGE_CACHE_MODE_UC,
 	[__pte2cm_idx( 0        | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_WB,
-	[__pte2cm_idx(_PAGE_PWT | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_WC,
+	[__pte2cm_idx(_PAGE_PWT | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx(0         | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC,
 };
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 4d28759f5a1a..62171cb2b0cb 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -68,8 +68,6 @@ static int __init pat_debug_setup(char *str)
 }
 __setup("debugpat", pat_debug_setup);
 
-static u64 __read_mostly boot_pat_state;
-
 #ifdef CONFIG_X86_PAT
 /*
  * X86 PAT uses page flags WC and Uncached together to keep track of
@@ -178,6 +176,7 @@ static void pat_bsp_init(u64 pat)
 {
 	enum page_cache_mode cache;
 	char pat_msg[33];
+	u64 tmp_pat;
 	int i;
 
 	if (!cpu_has_pat) {
@@ -185,14 +184,18 @@ static void pat_bsp_init(u64 pat)
 		return;
 	}
 
-	rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
-	if (!boot_pat_state) {
+	if (!pat_enabled())
+		goto done;
+
+	rdmsrl(MSR_IA32_CR_PAT, tmp_pat);
+	if (!tmp_pat) {
 		pat_disable("PAT MSR is 0, disabled.");
 		return;
 	}
 
 	wrmsrl(MSR_IA32_CR_PAT, pat);
 
+done:
 	pat_msg[32] = 0;
 
 	/*
@@ -209,6 +212,9 @@ static void pat_bsp_init(u64 pat)
 
 static void pat_ap_init(u64 pat)
 {
+	if (!pat_enabled())
+		return;
+
 	if (!cpu_has_pat) {
 		/*
 		 * If this happens we are on a secondary CPU, but switched to
@@ -224,25 +230,45 @@ void pat_init(void)
 {
 	u64 pat;
 
-	if (!pat_enabled())
-		return;
-
-	/*
-	 * Set PWT to Write-Combining. All other bits stay the same:
-	 *
-	 * PTE encoding used in Linux:
-	 *      PAT
-	 *      |PCD
-	 *      ||PWT
-	 *      |||
-	 *      000 WB		_PAGE_CACHE_WB
-	 *      001 WC		_PAGE_CACHE_WC
-	 *      010 UC-		_PAGE_CACHE_UC_MINUS
-	 *      011 UC		_PAGE_CACHE_UC
-	 * PAT bit unused
-	 */
-	pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
-	      PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
+	if (!pat_enabled()) {
+		/*
+		 * No PAT. Emulate the PAT table that corresponds to the two
+		 * cache bits, PWT (Write Through) and PCD (Cache Disable). This
+		 * setup is the same as the BIOS default setup when the system
+		 * has PAT but the "nopat" boot option has been specified. This
+		 * emulated PAT table is used when MSR_IA32_CR_PAT returns 0.
+		 *
+		 * PTE encoding used:
+		 *
+		 *       PCD
+		 *       |PWT  PAT
+		 *       ||    slot
+		 *       00    0    WB : _PAGE_CACHE_MODE_WB
+		 *       01    1    WT : _PAGE_CACHE_MODE_WT
+		 *       10    2    UC-: _PAGE_CACHE_MODE_UC_MINUS
+		 *       11    3    UC : _PAGE_CACHE_MODE_UC
+		 *
+		 * NOTE: When WC or WP is used, it is redirected to UC- per
+		 * the default setup in __cachemode2pte_tbl[].
+		 */
+		pat = PAT(0, WB) | PAT(1, WT) | PAT(2, UC_MINUS) | PAT(3, UC) |
+		      PAT(4, WB) | PAT(5, WT) | PAT(6, UC_MINUS) | PAT(7, UC);
+	} else {
+		/*
+		 * PTE encoding used in Linux:
+		 *      PAT
+		 *      |PCD
+		 *      ||PWT
+		 *      |||
+		 *      000 WB          _PAGE_CACHE_WB
+		 *      001 WC          _PAGE_CACHE_WC
+		 *      010 UC-         _PAGE_CACHE_UC_MINUS
+		 *      011 UC          _PAGE_CACHE_UC
+		 * PAT bit unused
+		 */
+		pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
+		      PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
+	}
 
 	if (!boot_cpu_done) {
 		pat_bsp_init(pat);
-- 
2.3.5

[PATCH 4/4] x86/pat: Remove pat_enabled() checks

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

Now that we emulate a PAT table when PAT is disabled, there's no need
for those checks anymore as the PAT abstraction will handle those cases
too.

Based on a conglomerate patch from Toshi Kani.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: arnd@arndb.de
Cc: Elliott@hp.com
Cc: hch@lst.de
Cc: hmh@hmh.eng.br
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: jgross@suse.com
Cc: konrad.wilk@oracle.com
Cc: linux-mm <linux-mm@kvack.org>
Cc: linux-nvdimm@lists.01.org
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: stefan.bader@canonical.com
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: x86-ml <x86@kernel.org>
Cc: yigal@plexistor.com
---
 arch/x86/mm/iomap_32.c | 12 ++++++------
 arch/x86/mm/ioremap.c  |  5 +----
 arch/x86/mm/pageattr.c |  3 ---
 arch/x86/mm/pat.c      | 13 +++----------
 4 files changed, 10 insertions(+), 23 deletions(-)

diff --git a/arch/x86/mm/iomap_32.c b/arch/x86/mm/iomap_32.c
index 3a2ec8790ca7..a9dc7a37e6a2 100644
--- a/arch/x86/mm/iomap_32.c
+++ b/arch/x86/mm/iomap_32.c
@@ -77,13 +77,13 @@ void __iomem *
 iomap_atomic_prot_pfn(unsigned long pfn, pgprot_t prot)
 {
 	/*
-	 * For non-PAT systems, promote PAGE_KERNEL_WC to PAGE_KERNEL_UC_MINUS.
-	 * PAGE_KERNEL_WC maps to PWT, which translates to uncached if the
-	 * MTRR is UC or WC.  UC_MINUS gets the real intention, of the
-	 * user, which is "WC if the MTRR is WC, UC if you can't do that."
+	 * For non-PAT systems, translate non-WB request to UC- just in
+	 * case the caller set the PWT bit to prot directly without using
+	 * pgprot_writecombine(). UC- translates to uncached if the MTRR
+	 * is UC or WC. UC- gets the real intention, of the user, which is
+	 * "WC if the MTRR is WC, UC if you can't do that."
 	 */
-	if (!pat_enabled() && pgprot_val(prot) ==
-	    (__PAGE_KERNEL | cachemode2protval(_PAGE_CACHE_MODE_WC)))
+	if (!pat_enabled() && pgprot2cachemode(prot) != _PAGE_CACHE_MODE_WB)
 		prot = __pgprot(__PAGE_KERNEL |
 				cachemode2protval(_PAGE_CACHE_MODE_UC_MINUS));
 
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index b0da3588b452..cc0f17c5ad9f 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -292,11 +292,8 @@ EXPORT_SYMBOL_GPL(ioremap_uc);
  */
 void __iomem *ioremap_wc(resource_size_t phys_addr, unsigned long size)
 {
-	if (pat_enabled())
-		return __ioremap_caller(phys_addr, size, _PAGE_CACHE_MODE_WC,
+	return __ioremap_caller(phys_addr, size, _PAGE_CACHE_MODE_WC,
 					__builtin_return_address(0));
-	else
-		return ioremap_nocache(phys_addr, size);
 }
 EXPORT_SYMBOL(ioremap_wc);
 
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 70d221fe2eb4..94aae76a5e06 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1571,9 +1571,6 @@ int set_memory_wc(unsigned long addr, int numpages)
 {
 	int ret;
 
-	if (!pat_enabled())
-		return set_memory_uc(addr, numpages);
-
 	ret = reserve_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE,
 		_PAGE_CACHE_MODE_WC, NULL);
 	if (ret)
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 62171cb2b0cb..e65555e0fe3d 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -432,12 +432,8 @@ int reserve_memtype(u64 start, u64 end, enum page_cache_mode req_type,
 
 	if (!pat_enabled()) {
 		/* This is identical to page table setting without PAT */
-		if (new_type) {
-			if (req_type == _PAGE_CACHE_MODE_WC)
-				*new_type = _PAGE_CACHE_MODE_UC_MINUS;
-			else
-				*new_type = req_type;
-		}
+		if (new_type)
+			*new_type = req_type;
 		return 0;
 	}
 
@@ -941,11 +937,8 @@ void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
 
 pgprot_t pgprot_writecombine(pgprot_t prot)
 {
-	if (pat_enabled())
-		return __pgprot(pgprot_val(prot) |
+	return __pgprot(pgprot_val(prot) |
 				cachemode2protval(_PAGE_CACHE_MODE_WC));
-	else
-		return pgprot_noncached(prot);
 }
 EXPORT_SYMBOL_GPL(pgprot_writecombine);
 
-- 
2.3.5

Re: [PATCH 2/4] x86/pat: Merge pat_init_cache_modes() into its caller

[Juergen Gross]

On 05/31/2015 11:48 AM, Borislav Petkov wrote:
> From: Borislav Petkov <bp@suse.de>
>
> This way we can pass pat MSR value directly.
>
> No functionality change.

You are breaking the Xen build with that change. pat_init_cache_modes()
is called from arch/x86/xen/enlighten.c as well.


Juergen

>
> Signed-off-by: Borislav Petkov <bp@suse.de>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Andy Lutomirski <luto@amacapital.net>
> Cc: arnd@arndb.de
> Cc: Elliott@hp.com
> Cc: hch@lst.de
> Cc: hmh@hmh.eng.br
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: jgross@suse.com
> Cc: konrad.wilk@oracle.com
> Cc: linux-mm <linux-mm@kvack.org>
> Cc: linux-nvdimm@lists.01.org
> Cc: Luis R. Rodriguez <mcgrof@suse.com>
> Cc: stefan.bader@canonical.com
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Toshi Kani <toshi.kani@hp.com>
> Cc: x86-ml <x86@kernel.org>
> Cc: yigal@plexistor.com
> ---
>   arch/x86/mm/pat.c | 39 ++++++++++++++++-----------------------
>   1 file changed, 16 insertions(+), 23 deletions(-)
>
> diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
> index 476d0780560f..4d28759f5a1a 100644
> --- a/arch/x86/mm/pat.c
> +++ b/arch/x86/mm/pat.c
> @@ -172,32 +172,14 @@ static enum page_cache_mode pat_get_cache_mode(unsigned pat_val, char *msg)
>
>   #undef CM
>
> -/*
> - * Update the cache mode to pgprot translation tables according to PAT
> - * configuration.
> - * Using lower indices is preferred, so we start with highest index.
> - */
> -void pat_init_cache_modes(void)
> -{
> -	int i;
> -	enum page_cache_mode cache;
> -	char pat_msg[33];
> -	u64 pat;
> -
> -	rdmsrl(MSR_IA32_CR_PAT, pat);
> -	pat_msg[32] = 0;
> -	for (i = 7; i >= 0; i--) {
> -		cache = pat_get_cache_mode((pat >> (i * 8)) & 7,
> -					   pat_msg + 4 * i);
> -		update_cache_mode_entry(i, cache);
> -	}
> -	pr_info("x86/PAT: Configuration [0-7]: %s\n", pat_msg);
> -}
> -
>   #define PAT(x, y)	((u64)PAT_ ## y << ((x)*8))
>
>   static void pat_bsp_init(u64 pat)
>   {
> +	enum page_cache_mode cache;
> +	char pat_msg[33];
> +	int i;
> +
>   	if (!cpu_has_pat) {
>   		pat_disable("PAT not supported by CPU.");
>   		return;
> @@ -211,7 +193,18 @@ static void pat_bsp_init(u64 pat)
>
>   	wrmsrl(MSR_IA32_CR_PAT, pat);
>
> -	pat_init_cache_modes();
> +	pat_msg[32] = 0;
> +
> +	/*
> +	 * Update the cache mode to pgprot translation tables according to PAT
> +	 * configuration. Using lower indices is preferred, so we start with
> +	 * highest index.
> +	 */
> +	for (i = 7; i >= 0; i--) {
> +		cache = pat_get_cache_mode((pat >> (i * 8)) & 7, pat_msg + 4 * i);
> +		update_cache_mode_entry(i, cache);
> +	}
> +	pr_info("x86/PAT: Configuration [0-7]: %s\n", pat_msg);
>   }
>
>   static void pat_ap_init(u64 pat)
>

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Re: [PATCH 2/4] x86/pat: Merge pat_init_cache_modes() into its caller

[Borislav Petkov]

On Sun, May 31, 2015 at 11:48:04AM +0200, Borislav Petkov wrote:
> From: Borislav Petkov <bp@suse.de>
> 
> This way we can pass pat MSR value directly.

This breaks xen as that function is used there, doh. :-\

Jürgen,

can you check the enlighten.c changes below please?

I'm reading xen's PAT config from MSR_IA32_CR_PAT and handing it down to
pat_init_cache_modes(). That shouldn't change current behavior AFAICT
because pat_init_cache_modes() did it itself before.

Right?

Thanks.

---
Author: Borislav Petkov <bp@suse.de>
Date:   Sat May 30 13:09:55 2015 +0200

    x86/pat: Emulate PAT when it is disabled
    
    In the case when PAT is disabled on the command line with "nopat" or
    when virtualization doesn't support PAT (correctly) - see
    
      9d34cfdf4796 ("x86: Don't rely on VMWare emulating PAT MSR correctly").
    
    we emulate it using the PWT and PCD cache attribute bits. Get rid of
    boot_pat_state while at it.
    
    Based on a conglomerate patch from Toshi Kani.
    
    Signed-off-by: Borislav Petkov <bp@suse.de>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: arnd@arndb.de
    Cc: Elliott@hp.com
    Cc: hch@lst.de
    Cc: hmh@hmh.eng.br
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: jgross@suse.com
    Cc: konrad.wilk@oracle.com
    Cc: linux-mm <linux-mm@kvack.org>
    Cc: linux-nvdimm@lists.01.org
    Cc: Luis R. Rodriguez <mcgrof@suse.com>
    Cc: stefan.bader@canonical.com
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Toshi Kani <toshi.kani@hp.com>
    Cc: x86-ml <x86@kernel.org>
    Cc: yigal@plexistor.com

diff --git a/arch/x86/include/asm/pat.h b/arch/x86/include/asm/pat.h
index cdcff7f7f694..ca6c228d5e62 100644
--- a/arch/x86/include/asm/pat.h
+++ b/arch/x86/include/asm/pat.h
@@ -6,7 +6,7 @@
 
 bool pat_enabled(void);
 extern void pat_init(void);
-void pat_init_cache_modes(void);
+void pat_init_cache_modes(u64);
 
 extern int reserve_memtype(u64 start, u64 end,
 		enum page_cache_mode req_pcm, enum page_cache_mode *ret_pcm);
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 1d553186c434..8533b46e6bee 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -40,7 +40,7 @@
  */
 uint16_t __cachemode2pte_tbl[_PAGE_CACHE_MODE_NUM] = {
 	[_PAGE_CACHE_MODE_WB      ]	= 0         | 0        ,
-	[_PAGE_CACHE_MODE_WC      ]	= _PAGE_PWT | 0        ,
+	[_PAGE_CACHE_MODE_WC      ]	= 0         | _PAGE_PCD,
 	[_PAGE_CACHE_MODE_UC_MINUS]	= 0         | _PAGE_PCD,
 	[_PAGE_CACHE_MODE_UC      ]	= _PAGE_PWT | _PAGE_PCD,
 	[_PAGE_CACHE_MODE_WT      ]	= 0         | _PAGE_PCD,
@@ -50,11 +50,11 @@ EXPORT_SYMBOL(__cachemode2pte_tbl);
 
 uint8_t __pte2cachemode_tbl[8] = {
 	[__pte2cm_idx( 0        | 0         | 0        )] = _PAGE_CACHE_MODE_WB,
-	[__pte2cm_idx(_PAGE_PWT | 0         | 0        )] = _PAGE_CACHE_MODE_WC,
+	[__pte2cm_idx(_PAGE_PWT | 0         | 0        )] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx( 0        | _PAGE_PCD | 0        )] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | 0        )] = _PAGE_CACHE_MODE_UC,
 	[__pte2cm_idx( 0        | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_WB,
-	[__pte2cm_idx(_PAGE_PWT | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_WC,
+	[__pte2cm_idx(_PAGE_PWT | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx(0         | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC,
 };
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 476d0780560f..6dc7826e4797 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -68,8 +68,6 @@ static int __init pat_debug_setup(char *str)
 }
 __setup("debugpat", pat_debug_setup);
 
-static u64 __read_mostly boot_pat_state;
-
 #ifdef CONFIG_X86_PAT
 /*
  * X86 PAT uses page flags WC and Uncached together to keep track of
@@ -177,14 +175,12 @@ static enum page_cache_mode pat_get_cache_mode(unsigned pat_val, char *msg)
  * configuration.
  * Using lower indices is preferred, so we start with highest index.
  */
-void pat_init_cache_modes(void)
+void pat_init_cache_modes(u64 pat)
 {
-	int i;
 	enum page_cache_mode cache;
 	char pat_msg[33];
-	u64 pat;
+	int i;
 
-	rdmsrl(MSR_IA32_CR_PAT, pat);
 	pat_msg[32] = 0;
 	for (i = 7; i >= 0; i--) {
 		cache = pat_get_cache_mode((pat >> (i * 8)) & 7,
@@ -198,24 +194,33 @@ void pat_init_cache_modes(void)
 
 static void pat_bsp_init(u64 pat)
 {
+	u64 tmp_pat;
+
 	if (!cpu_has_pat) {
 		pat_disable("PAT not supported by CPU.");
 		return;
 	}
 
-	rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
-	if (!boot_pat_state) {
+	if (!pat_enabled())
+		goto done;
+
+	rdmsrl(MSR_IA32_CR_PAT, tmp_pat);
+	if (!tmp_pat) {
 		pat_disable("PAT MSR is 0, disabled.");
 		return;
 	}
 
 	wrmsrl(MSR_IA32_CR_PAT, pat);
 
-	pat_init_cache_modes();
+done:
+	pat_init_cache_modes(pat);
 }
 
 static void pat_ap_init(u64 pat)
 {
+	if (!pat_enabled())
+		return;
+
 	if (!cpu_has_pat) {
 		/*
 		 * If this happens we are on a secondary CPU, but switched to
@@ -231,25 +236,45 @@ void pat_init(void)
 {
 	u64 pat;
 
-	if (!pat_enabled())
-		return;
-
-	/*
-	 * Set PWT to Write-Combining. All other bits stay the same:
-	 *
-	 * PTE encoding used in Linux:
-	 *      PAT
-	 *      |PCD
-	 *      ||PWT
-	 *      |||
-	 *      000 WB		_PAGE_CACHE_WB
-	 *      001 WC		_PAGE_CACHE_WC
-	 *      010 UC-		_PAGE_CACHE_UC_MINUS
-	 *      011 UC		_PAGE_CACHE_UC
-	 * PAT bit unused
-	 */
-	pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
-	      PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
+	if (!pat_enabled()) {
+		/*
+		 * No PAT. Emulate the PAT table that corresponds to the two
+		 * cache bits, PWT (Write Through) and PCD (Cache Disable). This
+		 * setup is the same as the BIOS default setup when the system
+		 * has PAT but the "nopat" boot option has been specified. This
+		 * emulated PAT table is used when MSR_IA32_CR_PAT returns 0.
+		 *
+		 * PTE encoding used:
+		 *
+		 *       PCD
+		 *       |PWT  PAT
+		 *       ||    slot
+		 *       00    0    WB : _PAGE_CACHE_MODE_WB
+		 *       01    1    WT : _PAGE_CACHE_MODE_WT
+		 *       10    2    UC-: _PAGE_CACHE_MODE_UC_MINUS
+		 *       11    3    UC : _PAGE_CACHE_MODE_UC
+		 *
+		 * NOTE: When WC or WP is used, it is redirected to UC- per
+		 * the default setup in __cachemode2pte_tbl[].
+		 */
+		pat = PAT(0, WB) | PAT(1, WT) | PAT(2, UC_MINUS) | PAT(3, UC) |
+		      PAT(4, WB) | PAT(5, WT) | PAT(6, UC_MINUS) | PAT(7, UC);
+	} else {
+		/*
+		 * PTE encoding used in Linux:
+		 *      PAT
+		 *      |PCD
+		 *      ||PWT
+		 *      |||
+		 *      000 WB          _PAGE_CACHE_WB
+		 *      001 WC          _PAGE_CACHE_WC
+		 *      010 UC-         _PAGE_CACHE_UC_MINUS
+		 *      011 UC          _PAGE_CACHE_UC
+		 * PAT bit unused
+		 */
+		pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
+		      PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
+	}
 
 	if (!boot_cpu_done) {
 		pat_bsp_init(pat);
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 46957ead3060..53233a9beea9 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1467,6 +1467,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
 {
 	struct physdev_set_iopl set_iopl;
 	unsigned long initrd_start = 0;
+	u64 pat;
 	int rc;
 
 	if (!xen_start_info)
@@ -1574,8 +1575,8 @@ asmlinkage __visible void __init xen_start_kernel(void)
 	 * Modify the cache mode translation tables to match Xen's PAT
 	 * configuration.
 	 */
-
-	pat_init_cache_modes();
+	rdmsrl(MSR_IA32_CR_PAT, pat);
+	pat_init_cache_modes(pat);
 
 	/* keep using Xen gdt for now; no urgent need to change it */
 


-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--

Re: [PATCH 2/4] x86/pat: Merge pat_init_cache_modes() into its caller

[Borislav Petkov]

On Sun, May 31, 2015 at 12:15:21PM +0200, Juergen Gross wrote:
> You are breaking the Xen build with that change. pat_init_cache_modes()
> is called from arch/x86/xen/enlighten.c as well.

Yeah, build-robot just caught that. Can you please check the enlighten.c
change in the other mail I just sent?

Thanks.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--

Re: [PATCH 2/4] x86/pat: Merge pat_init_cache_modes() into its caller

[Juergen Gross]

On 05/31/2015 12:23 PM, Borislav Petkov wrote:
> On Sun, May 31, 2015 at 11:48:04AM +0200, Borislav Petkov wrote:
>> From: Borislav Petkov <bp@suse.de>
>>
>> This way we can pass pat MSR value directly.
>
> This breaks xen as that function is used there, doh. :-\
>
> JA 1/4 rgen,
>
> can you check the enlighten.c changes below please?

Acked-by: Juergen Gross <jgross@suse.com>

>
> I'm reading xen's PAT config from MSR_IA32_CR_PAT and handing it down to
> pat_init_cache_modes(). That shouldn't change current behavior AFAICT
> because pat_init_cache_modes() did it itself before.
>
> Right?
>
> Thanks.
>
> ---
> Author: Borislav Petkov <bp@suse.de>
> Date:   Sat May 30 13:09:55 2015 +0200
>
>      x86/pat: Emulate PAT when it is disabled
>
>      In the case when PAT is disabled on the command line with "nopat" or
>      when virtualization doesn't support PAT (correctly) - see
>
>        9d34cfdf4796 ("x86: Don't rely on VMWare emulating PAT MSR correctly").
>
>      we emulate it using the PWT and PCD cache attribute bits. Get rid of
>      boot_pat_state while at it.
>
>      Based on a conglomerate patch from Toshi Kani.
>
>      Signed-off-by: Borislav Petkov <bp@suse.de>
>      Cc: Andrew Morton <akpm@linux-foundation.org>
>      Cc: Andy Lutomirski <luto@amacapital.net>
>      Cc: arnd@arndb.de
>      Cc: Elliott@hp.com
>      Cc: hch@lst.de
>      Cc: hmh@hmh.eng.br
>      Cc: H. Peter Anvin <hpa@zytor.com>
>      Cc: Ingo Molnar <mingo@redhat.com>
>      Cc: jgross@suse.com
>      Cc: konrad.wilk@oracle.com
>      Cc: linux-mm <linux-mm@kvack.org>
>      Cc: linux-nvdimm@lists.01.org
>      Cc: Luis R. Rodriguez <mcgrof@suse.com>
>      Cc: stefan.bader@canonical.com
>      Cc: Thomas Gleixner <tglx@linutronix.de>
>      Cc: Toshi Kani <toshi.kani@hp.com>
>      Cc: x86-ml <x86@kernel.org>
>      Cc: yigal@plexistor.com
>
> diff --git a/arch/x86/include/asm/pat.h b/arch/x86/include/asm/pat.h
> index cdcff7f7f694..ca6c228d5e62 100644
> --- a/arch/x86/include/asm/pat.h
> +++ b/arch/x86/include/asm/pat.h
> @@ -6,7 +6,7 @@
>
>   bool pat_enabled(void);
>   extern void pat_init(void);
> -void pat_init_cache_modes(void);
> +void pat_init_cache_modes(u64);
>
>   extern int reserve_memtype(u64 start, u64 end,
>   		enum page_cache_mode req_pcm, enum page_cache_mode *ret_pcm);
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index 1d553186c434..8533b46e6bee 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -40,7 +40,7 @@
>    */
>   uint16_t __cachemode2pte_tbl[_PAGE_CACHE_MODE_NUM] = {
>   	[_PAGE_CACHE_MODE_WB      ]	= 0         | 0        ,
> -	[_PAGE_CACHE_MODE_WC      ]	= _PAGE_PWT | 0        ,
> +	[_PAGE_CACHE_MODE_WC      ]	= 0         | _PAGE_PCD,
>   	[_PAGE_CACHE_MODE_UC_MINUS]	= 0         | _PAGE_PCD,
>   	[_PAGE_CACHE_MODE_UC      ]	= _PAGE_PWT | _PAGE_PCD,
>   	[_PAGE_CACHE_MODE_WT      ]	= 0         | _PAGE_PCD,
> @@ -50,11 +50,11 @@ EXPORT_SYMBOL(__cachemode2pte_tbl);
>
>   uint8_t __pte2cachemode_tbl[8] = {
>   	[__pte2cm_idx( 0        | 0         | 0        )] = _PAGE_CACHE_MODE_WB,
> -	[__pte2cm_idx(_PAGE_PWT | 0         | 0        )] = _PAGE_CACHE_MODE_WC,
> +	[__pte2cm_idx(_PAGE_PWT | 0         | 0        )] = _PAGE_CACHE_MODE_UC_MINUS,
>   	[__pte2cm_idx( 0        | _PAGE_PCD | 0        )] = _PAGE_CACHE_MODE_UC_MINUS,
>   	[__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | 0        )] = _PAGE_CACHE_MODE_UC,
>   	[__pte2cm_idx( 0        | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_WB,
> -	[__pte2cm_idx(_PAGE_PWT | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_WC,
> +	[__pte2cm_idx(_PAGE_PWT | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS,
>   	[__pte2cm_idx(0         | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS,
>   	[__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC,
>   };
> diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
> index 476d0780560f..6dc7826e4797 100644
> --- a/arch/x86/mm/pat.c
> +++ b/arch/x86/mm/pat.c
> @@ -68,8 +68,6 @@ static int __init pat_debug_setup(char *str)
>   }
>   __setup("debugpat", pat_debug_setup);
>
> -static u64 __read_mostly boot_pat_state;
> -
>   #ifdef CONFIG_X86_PAT
>   /*
>    * X86 PAT uses page flags WC and Uncached together to keep track of
> @@ -177,14 +175,12 @@ static enum page_cache_mode pat_get_cache_mode(unsigned pat_val, char *msg)
>    * configuration.
>    * Using lower indices is preferred, so we start with highest index.
>    */
> -void pat_init_cache_modes(void)
> +void pat_init_cache_modes(u64 pat)
>   {
> -	int i;
>   	enum page_cache_mode cache;
>   	char pat_msg[33];
> -	u64 pat;
> +	int i;
>
> -	rdmsrl(MSR_IA32_CR_PAT, pat);
>   	pat_msg[32] = 0;
>   	for (i = 7; i >= 0; i--) {
>   		cache = pat_get_cache_mode((pat >> (i * 8)) & 7,
> @@ -198,24 +194,33 @@ void pat_init_cache_modes(void)
>
>   static void pat_bsp_init(u64 pat)
>   {
> +	u64 tmp_pat;
> +
>   	if (!cpu_has_pat) {
>   		pat_disable("PAT not supported by CPU.");
>   		return;
>   	}
>
> -	rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
> -	if (!boot_pat_state) {
> +	if (!pat_enabled())
> +		goto done;
> +
> +	rdmsrl(MSR_IA32_CR_PAT, tmp_pat);
> +	if (!tmp_pat) {
>   		pat_disable("PAT MSR is 0, disabled.");
>   		return;
>   	}
>
>   	wrmsrl(MSR_IA32_CR_PAT, pat);
>
> -	pat_init_cache_modes();
> +done:
> +	pat_init_cache_modes(pat);
>   }
>
>   static void pat_ap_init(u64 pat)
>   {
> +	if (!pat_enabled())
> +		return;
> +
>   	if (!cpu_has_pat) {
>   		/*
>   		 * If this happens we are on a secondary CPU, but switched to
> @@ -231,25 +236,45 @@ void pat_init(void)
>   {
>   	u64 pat;
>
> -	if (!pat_enabled())
> -		return;
> -
> -	/*
> -	 * Set PWT to Write-Combining. All other bits stay the same:
> -	 *
> -	 * PTE encoding used in Linux:
> -	 *      PAT
> -	 *      |PCD
> -	 *      ||PWT
> -	 *      |||
> -	 *      000 WB		_PAGE_CACHE_WB
> -	 *      001 WC		_PAGE_CACHE_WC
> -	 *      010 UC-		_PAGE_CACHE_UC_MINUS
> -	 *      011 UC		_PAGE_CACHE_UC
> -	 * PAT bit unused
> -	 */
> -	pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
> -	      PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
> +	if (!pat_enabled()) {
> +		/*
> +		 * No PAT. Emulate the PAT table that corresponds to the two
> +		 * cache bits, PWT (Write Through) and PCD (Cache Disable). This
> +		 * setup is the same as the BIOS default setup when the system
> +		 * has PAT but the "nopat" boot option has been specified. This
> +		 * emulated PAT table is used when MSR_IA32_CR_PAT returns 0.
> +		 *
> +		 * PTE encoding used:
> +		 *
> +		 *       PCD
> +		 *       |PWT  PAT
> +		 *       ||    slot
> +		 *       00    0    WB : _PAGE_CACHE_MODE_WB
> +		 *       01    1    WT : _PAGE_CACHE_MODE_WT
> +		 *       10    2    UC-: _PAGE_CACHE_MODE_UC_MINUS
> +		 *       11    3    UC : _PAGE_CACHE_MODE_UC
> +		 *
> +		 * NOTE: When WC or WP is used, it is redirected to UC- per
> +		 * the default setup in __cachemode2pte_tbl[].
> +		 */
> +		pat = PAT(0, WB) | PAT(1, WT) | PAT(2, UC_MINUS) | PAT(3, UC) |
> +		      PAT(4, WB) | PAT(5, WT) | PAT(6, UC_MINUS) | PAT(7, UC);
> +	} else {
> +		/*
> +		 * PTE encoding used in Linux:
> +		 *      PAT
> +		 *      |PCD
> +		 *      ||PWT
> +		 *      |||
> +		 *      000 WB          _PAGE_CACHE_WB
> +		 *      001 WC          _PAGE_CACHE_WC
> +		 *      010 UC-         _PAGE_CACHE_UC_MINUS
> +		 *      011 UC          _PAGE_CACHE_UC
> +		 * PAT bit unused
> +		 */
> +		pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
> +		      PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
> +	}
>
>   	if (!boot_cpu_done) {
>   		pat_bsp_init(pat);
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 46957ead3060..53233a9beea9 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1467,6 +1467,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
>   {
>   	struct physdev_set_iopl set_iopl;
>   	unsigned long initrd_start = 0;
> +	u64 pat;
>   	int rc;
>
>   	if (!xen_start_info)
> @@ -1574,8 +1575,8 @@ asmlinkage __visible void __init xen_start_kernel(void)
>   	 * Modify the cache mode translation tables to match Xen's PAT
>   	 * configuration.
>   	 */
> -
> -	pat_init_cache_modes();
> +	rdmsrl(MSR_IA32_CR_PAT, pat);
> +	pat_init_cache_modes(pat);
>
>   	/* keep using Xen gdt for now; no urgent need to change it */
>
>
>

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Re: [PATCH v11 2/12] x86, mm, pat: Refactor !pat_enabled handling

[Toshi Kani]

On Sun, 2015-05-31 at 11:46 +0200, Borislav Petkov wrote:
> On Fri, May 29, 2015 at 04:59:00PM -0600, Toshi Kani wrote:
> > From: Toshi Kani <toshi.kani@hp.com>
> > 
> > This patch refactors the !pat_enabled code paths and integrates
> > them into the PAT abstraction code.  The PAT table is emulated by
> > corresponding to the two cache attribute bits, PWT (Write Through)
> > and PCD (Cache Disable).  The emulated PAT table is the same as the
> > BIOS default setup when the system has PAT but the "nopat" boot
> > option is specified.  The emulated PAT table is also used when
> > MSR_IA32_CR_PAT returns 0 -- 9d34cfdf4796 ("x86: Don't rely on
> > VMWare emulating PAT MSR correctly").
> 
> To be honest, I wasn't surprised when you sent me the same patch and
> ignored most of my comments. For the future, please let me know if I'm
> wasting my time with commenting on your stuff so that I can plan my work
> and not waste time and energy reviewing, ok?

I apologize that I overlooked a comment requesting to divide this
refactor patch into smaller patches.

> Unfortunately, if you want something done right, you have to do it
> yourself.
>
> So I did that, I split that ugly cleanup into something much more
> readable, patches as a reply to this message.
> 
> Feel free to base your work ontop of
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/bp/bp.git#tip-mm-2
> 

I will look into your changes, and rebase the patchset.

Thanks,
-Toshi

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Re: [PATCH 1/4] x86/pat: Untangle pat_init()

[Toshi Kani]

On Sun, 2015-05-31 at 11:48 +0200, Borislav Petkov wrote:
> From: Borislav Petkov <bp@suse.de>
> 
> Split it into a BSP and AP version which makes the PAT initialization
> path actually readable again.
> 
> Signed-off-by: Borislav Petkov <bp@suse.de>

Reviewed-by: Toshi Kani <toshi.kani@hp.com>

Thanks,
-Toshi


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Re: [PATCH 2/4] x86/pat: Merge pat_init_cache_modes() into its caller

[Toshi Kani]

On Sun, 2015-05-31 at 12:23 +0200, Borislav Petkov wrote:
> On Sun, May 31, 2015 at 11:48:04AM +0200, Borislav Petkov wrote:
> > From: Borislav Petkov <bp@suse.de>
> > 
> > This way we can pass pat MSR value directly.
> 
> This breaks xen as that function is used there, doh. :-\
> 
> JA 1/4 rgen,
> 
> can you check the enlighten.c changes below please?
> 
> I'm reading xen's PAT config from MSR_IA32_CR_PAT and handing it down to
> pat_init_cache_modes(). That shouldn't change current behavior AFAICT
> because pat_init_cache_modes() did it itself before.
> 
> Right?
> 
> Thanks.
> 
> ---
> Author: Borislav Petkov <bp@suse.de>
> Date:   Sat May 30 13:09:55 2015 +0200
> 
>     x86/pat: Emulate PAT when it is disabled
>     
>     In the case when PAT is disabled on the command line with "nopat" or
>     when virtualization doesn't support PAT (correctly) - see
>     
>       9d34cfdf4796 ("x86: Don't rely on VMWare emulating PAT MSR correctly").
>     
>     we emulate it using the PWT and PCD cache attribute bits. Get rid of
>     boot_pat_state while at it.
>     
>     Based on a conglomerate patch from Toshi Kani.
>     
>     Signed-off-by: Borislav Petkov <bp@suse.de>

Reviewed-by: Toshi Kani <toshi.kani@hp.com>

Thanks,
-Toshi



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Re: [PATCH 4/4] x86/pat: Remove pat_enabled() checks

[Toshi Kani]

On Sun, 2015-05-31 at 11:48 +0200, Borislav Petkov wrote:
> From: Borislav Petkov <bp@suse.de>
> 
> Now that we emulate a PAT table when PAT is disabled, there's no need
> for those checks anymore as the PAT abstraction will handle those cases
> too.
> 
> Based on a conglomerate patch from Toshi Kani.
> 
> Signed-off-by: Borislav Petkov <bp@suse.de>

I reviewed the 1/3-3/3 patchset in your "tip-mm-2" branch, which is
different from this submitted patchset 1/4-4/4.  So, my review-by
applies to the 3 patches in the "tip-mm-2" branch.

Reviewed-by: Toshi Kani <toshi.kani@hp.com>

Thanks,
-Toshi

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Re: [PATCH 4/4] x86/pat: Remove pat_enabled() checks

[Borislav Petkov]

On Mon, Jun 01, 2015 at 12:26:29PM -0600, Toshi Kani wrote:
> I reviewed the 1/3-3/3 patchset in your "tip-mm-2" branch, which is
> different from this submitted patchset 1/4-4/4. So, my review-by
> applies to the 3 patches in the "tip-mm-2" branch.

That's fine, the 4 patches were broken due to xen using
pat_init_cache_modes() too. So the 3 are the right ones.

Thanks.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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