[PATCH 0/4] Update cpu feature extraction

[PATCH 0/4] Update cpu feature extraction

[Vladimir Murzin]

Hi,

This has been started as a fix in cpu feature extractor, but Suzuki suggested
syncing-up the whole cpu feature handling with the recent updates on arm64
side [1,2].

I've kept fixes separately, so they can go as the are in case there is concern
on updating cpu feature handling.

[1] http://comments.gmane.org/gmane.linux.ports.arm.kernel/455568
[2] https://lkml.org/lkml/2015/11/18/570

Thanks!

Vladimir Murzin (4):
  ARM: fix demoting HWCAP_SWP
  ARM: fix cpu feature extracting helper
  ARM: introduce cpu feature helper for unsigned values
  ARM: use proper helper while extracting cpu features

 arch/arm/include/asm/cputype.h  |   16 +++++++++++++---
 arch/arm/include/asm/smp_plat.h |    4 ++--
 arch/arm/kernel/setup.c         |   34 ++++++++++++++++++++--------------
 arch/arm/kernel/thumbee.c       |    4 +---
 arch/arm/mm/mmu.c               |    2 +-
 5 files changed, 37 insertions(+), 23 deletions(-)

-- 
1.7.9.5

[PATCH 1/4] ARM: fix demoting HWCAP_SWP

[Vladimir Murzin]

Commit b8c9592 "ARM: 8318/1: treat CPU feature register fields as signed
quantities" accidentally altered cpuid register used to demote
HWCAP_SWP.
ARM ARM says that SyncPrim_instrs bits in ID_ISAR3 should be used with
SynchPrim_instrs_frac from ID_ISAR4. So, follow this rule.

Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
 arch/arm/kernel/setup.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 7d0cba6f..fde041b 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -510,7 +510,7 @@ static void __init elf_hwcap_fixup(void)
 	 */
 	if (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) > 1 ||
 	    (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) == 1 &&
-	     cpuid_feature_extract(CPUID_EXT_ISAR3, 20) >= 3))
+	     cpuid_feature_extract(CPUID_EXT_ISAR4, 20) >= 3))
 		elf_hwcap &= ~HWCAP_SWP;
 }
 
-- 
1.7.9.5

[PATCH 1/4] ARM: fix demoting HWCAP_SWP

[Ard Biesheuvel]

On 26 January 2016 at 10:23, Vladimir Murzin <vladimir.murzin@arm.com> wrote:
> Commit b8c9592 "ARM: 8318/1: treat CPU feature register fields as signed
> quantities" accidentally altered cpuid register used to demote
> HWCAP_SWP.
> ARM ARM says that SyncPrim_instrs bits in ID_ISAR3 should be used with
> SynchPrim_instrs_frac from ID_ISAR4. So, follow this rule.
>
> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Apologies for breaking that ...

> ---
>  arch/arm/kernel/setup.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index 7d0cba6f..fde041b 100644
> --- a/arch/arm/kernel/setup.c
> +++ b/arch/arm/kernel/setup.c
> @@ -510,7 +510,7 @@ static void __init elf_hwcap_fixup(void)
>          */
>         if (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) > 1 ||
>             (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) == 1 &&
> -            cpuid_feature_extract(CPUID_EXT_ISAR3, 20) >= 3))
> +            cpuid_feature_extract(CPUID_EXT_ISAR4, 20) >= 3))
>                 elf_hwcap &= ~HWCAP_SWP;
>  }
>
> --
> 1.7.9.5
>

[PATCH 2/4] ARM: fix cpu feature extracting helper

[Vladimir Murzin]

Commit b8c9592 "ARM: 8318/1: treat CPU feature register fields as signed
quantities" introduced helper to extract signed quantities of 4-bit
blocks. However, with a current code feature with value 0b1000 isn't
rejected as negative. So fix the "if" condition.

Reported-by: Jonathan Brawn <Jon.Brawn@arm.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
 arch/arm/include/asm/cputype.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/cputype.h b/arch/arm/include/asm/cputype.h
index b23c6c8..1ee94c7 100644
--- a/arch/arm/include/asm/cputype.h
+++ b/arch/arm/include/asm/cputype.h
@@ -276,7 +276,7 @@ static inline int __attribute_const__ cpuid_feature_extract_field(u32 features,
 	int feature = (features >> field) & 15;
 
 	/* feature registers are signed values */
-	if (feature > 8)
+	if (feature > 7)
 		feature -= 16;
 
 	return feature;
-- 
1.7.9.5

[PATCH 2/4] ARM: fix cpu feature extracting helper

[Ard Biesheuvel]

On 26 January 2016 at 10:23, Vladimir Murzin <vladimir.murzin@arm.com> wrote:
> Commit b8c9592 "ARM: 8318/1: treat CPU feature register fields as signed
> quantities" introduced helper to extract signed quantities of 4-bit
> blocks. However, with a current code feature with value 0b1000 isn't
> rejected as negative. So fix the "if" condition.
>
> Reported-by: Jonathan Brawn <Jon.Brawn@arm.com>
> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> ---
>  arch/arm/include/asm/cputype.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/include/asm/cputype.h b/arch/arm/include/asm/cputype.h
> index b23c6c8..1ee94c7 100644
> --- a/arch/arm/include/asm/cputype.h
> +++ b/arch/arm/include/asm/cputype.h
> @@ -276,7 +276,7 @@ static inline int __attribute_const__ cpuid_feature_extract_field(u32 features,
>         int feature = (features >> field) & 15;
>
>         /* feature registers are signed values */
> -       if (feature > 8)
> +       if (feature > 7)
>                 feature -= 16;
>
>         return feature;
> --
> 1.7.9.5
>

[PATCH 3/4] ARM: introduce cpu feature helper for unsigned values

[Vladimir Murzin]

Some of the CPU feature bits have unsigned values and need to be treated
accordingly to avoid errors. Add the new cpu feature helper for such
cases.

Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
 arch/arm/include/asm/cputype.h |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/cputype.h b/arch/arm/include/asm/cputype.h
index 1ee94c7..d93ced5 100644
--- a/arch/arm/include/asm/cputype.h
+++ b/arch/arm/include/asm/cputype.h
@@ -270,8 +270,15 @@ static inline int cpu_is_pj4(void)
 #define cpu_is_pj4()	0
 #endif
 
-static inline int __attribute_const__ cpuid_feature_extract_field(u32 features,
-								  int field)
+
+static inline unsigned int __attribute_const__
+cpuid_feature_extract_unsigned_field(u32 features, int field)
+{
+	return (features >> field) & 15;
+}
+
+static inline int __attribute_const__
+cpuid_feature_extract_field(u32 features, int field)
 {
 	int feature = (features >> field) & 15;
 
@@ -285,4 +292,7 @@ static inline int __attribute_const__ cpuid_feature_extract_field(u32 features,
 #define cpuid_feature_extract(reg, field) \
 	cpuid_feature_extract_field(read_cpuid_ext(reg), field)
 
+#define cpuid_feature_extract_unsigned(reg, field) \
+	cpuid_feature_extract_unsigned_field(read_cpuid_ext(reg), field)
+
 #endif
-- 
1.7.9.5

[PATCH 4/4] ARM: use proper helper while extracting cpu features

[Vladimir Murzin]

Update current users of cpu feature helpers to use the proper helper
depends on how feature bits should be handled. We follow the arm64
scheme [1] (slightly rephrased):

We have three types of fields:

a) A precise value or a value from which you derive some precise
   value.
b) Fields defining the presence of a feature (1, 2, 3). These would
   always be positive since the absence of such feature would mean a
   value of 0
c) Fields defining the absence of a feature by setting 0xf. These are
   usually fields that were initial RAZ and turned to -1.

So we can treat (a) and (b) as unsigned permanently and (c) as as
signed,

[1] https://lkml.org/lkml/2015/11/19/549

Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
 arch/arm/include/asm/smp_plat.h |    4 ++--
 arch/arm/kernel/setup.c         |   34 ++++++++++++++++++++--------------
 arch/arm/kernel/thumbee.c       |    4 +---
 arch/arm/mm/mmu.c               |    2 +-
 4 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/arch/arm/include/asm/smp_plat.h b/arch/arm/include/asm/smp_plat.h
index f908071..03bbe02 100644
--- a/arch/arm/include/asm/smp_plat.h
+++ b/arch/arm/include/asm/smp_plat.h
@@ -49,7 +49,7 @@ static inline int tlb_ops_need_broadcast(void)
 	if (!is_smp())
 		return 0;
 
-	return ((read_cpuid_ext(CPUID_EXT_MMFR3) >> 12) & 0xf) < 2;
+	return cpuid_feature_extract_unsigned(CPUID_EXT_MMFR3, 12) < 2;
 }
 #endif
 
@@ -61,7 +61,7 @@ static inline int cache_ops_need_broadcast(void)
 	if (!is_smp())
 		return 0;
 
-	return ((read_cpuid_ext(CPUID_EXT_MMFR3) >> 12) & 0xf) < 1;
+	return cpuid_feature_extract_unsigned(CPUID_EXT_MMFR3, 12) < 1;
 }
 #endif
 
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index fde041b..e696553 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -257,11 +257,15 @@ static int __get_cpu_architecture(void)
 		/* Revised CPUID format. Read the Memory Model Feature
 		 * Register 0 and check for VMSAv7 or PMSAv7 */
 		unsigned int mmfr0 = read_cpuid_ext(CPUID_EXT_MMFR0);
-		if ((mmfr0 & 0x0000000f) >= 0x00000003 ||
-		    (mmfr0 & 0x000000f0) >= 0x00000030)
+		unsigned int block;
+#ifdef CONFIG_MMU
+		block = cpuid_feature_extract_unsigned_field(mmfr0, 0);
+#else
+		block = cpuid_feature_extract_unsigned_field(mmfr0, 4);
+#endif
+		if (mmfr0 >= 3)
 			cpu_arch = CPU_ARCH_ARMv7;
-		else if ((mmfr0 & 0x0000000f) == 0x00000002 ||
-			 (mmfr0 & 0x000000f0) == 0x00000020)
+		else if (mmfr0 == 2)
 			cpu_arch = CPU_ARCH_ARMv6;
 		else
 			cpu_arch = CPU_ARCH_UNKNOWN;
@@ -446,41 +450,41 @@ static inline void patch_aeabi_idiv(void) { }
 
 static void __init cpuid_init_hwcaps(void)
 {
-	int block;
+	unsigned int block;
 	u32 isar5;
 
 	if (cpu_architecture() < CPU_ARCH_ARMv7)
 		return;
 
-	block = cpuid_feature_extract(CPUID_EXT_ISAR0, 24);
+	block = cpuid_feature_extract_unsigned(CPUID_EXT_ISAR0, 24);
 	if (block >= 2)
 		elf_hwcap |= HWCAP_IDIVA;
 	if (block >= 1)
 		elf_hwcap |= HWCAP_IDIVT;
 
 	/* LPAE implies atomic ldrd/strd instructions */
-	block = cpuid_feature_extract(CPUID_EXT_MMFR0, 0);
+	block = cpuid_feature_extract_unsigned(CPUID_EXT_MMFR0, 0);
 	if (block >= 5)
 		elf_hwcap |= HWCAP_LPAE;
 
 	/* check for supported v8 Crypto instructions */
 	isar5 = read_cpuid_ext(CPUID_EXT_ISAR5);
 
-	block = cpuid_feature_extract_field(isar5, 4);
+	block = cpuid_feature_extract_unsigned_field(isar5, 4);
 	if (block >= 2)
 		elf_hwcap2 |= HWCAP2_PMULL;
 	if (block >= 1)
 		elf_hwcap2 |= HWCAP2_AES;
 
-	block = cpuid_feature_extract_field(isar5, 8);
+	block = cpuid_feature_extract_unsigned_field(isar5, 8);
 	if (block >= 1)
 		elf_hwcap2 |= HWCAP2_SHA1;
 
-	block = cpuid_feature_extract_field(isar5, 12);
+	block = cpuid_feature_extract_unsigned_field(isar5, 12);
 	if (block >= 1)
 		elf_hwcap2 |= HWCAP2_SHA2;
 
-	block = cpuid_feature_extract_field(isar5, 16);
+	block = cpuid_feature_extract_unsigned_field(isar5, 16);
 	if (block >= 1)
 		elf_hwcap2 |= HWCAP2_CRC32;
 }
@@ -488,6 +492,7 @@ static void __init cpuid_init_hwcaps(void)
 static void __init elf_hwcap_fixup(void)
 {
 	unsigned id = read_cpuid_id();
+	unsigned int block;
 
 	/*
 	 * HWCAP_TLS is available only on 1136 r1p0 and later,
@@ -508,9 +513,10 @@ static void __init elf_hwcap_fixup(void)
 	 * avoid advertising SWP; it may not be atomic with
 	 * multiprocessing cores.
 	 */
-	if (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) > 1 ||
-	    (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) == 1 &&
-	     cpuid_feature_extract(CPUID_EXT_ISAR4, 20) >= 3))
+	block = cpuid_feature_extract_unsigned(CPUID_EXT_ISAR3, 12);
+
+	if (block > 1 || (block == 1 &&
+	    cpuid_feature_extract_unsigned(CPUID_EXT_ISAR4, 20) >= 3))
 		elf_hwcap &= ~HWCAP_SWP;
 }
 
diff --git a/arch/arm/kernel/thumbee.c b/arch/arm/kernel/thumbee.c
index 8ff8dbf..b5cac80 100644
--- a/arch/arm/kernel/thumbee.c
+++ b/arch/arm/kernel/thumbee.c
@@ -62,14 +62,12 @@ static struct notifier_block thumbee_notifier_block = {
 
 static int __init thumbee_init(void)
 {
-	unsigned long pfr0;
 	unsigned int cpu_arch = cpu_architecture();
 
 	if (cpu_arch < CPU_ARCH_ARMv7)
 		return 0;
 
-	pfr0 = read_cpuid_ext(CPUID_EXT_PFR0);
-	if ((pfr0 & 0x0000f000) != 0x00001000)
+	if (cpuid_feature_extract_unsigned(CPUID_EXT_PFR0, 12) != 1)
 		return 0;
 
 	pr_info("ThumbEE CPU extension supported.\n");
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 434d76f..06723a9 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -572,7 +572,7 @@ static void __init build_mem_type_table(void)
 	 * in the Short-descriptor translation table format descriptors.
 	 */
 	if (cpu_arch == CPU_ARCH_ARMv7 &&
-		(read_cpuid_ext(CPUID_EXT_MMFR0) & 0xF) >= 4) {
+		(cpuid_feature_extract_unsigned(CPUID_EXT_MMFR0, 0) >= 4)) {
 		user_pmd_table |= PMD_PXNTABLE;
 	}
 #endif
-- 
1.7.9.5

[PATCH 4/4] ARM: use proper helper while extracting cpu features

[Ard Biesheuvel]

On 26 January 2016 at 10:23, Vladimir Murzin <vladimir.murzin@arm.com> wrote:
> Update current users of cpu feature helpers to use the proper helper
> depends on how feature bits should be handled. We follow the arm64
> scheme [1] (slightly rephrased):
>
> We have three types of fields:
>
> a) A precise value or a value from which you derive some precise
>    value.
> b) Fields defining the presence of a feature (1, 2, 3). These would
>    always be positive since the absence of such feature would mean a
>    value of 0
> c) Fields defining the absence of a feature by setting 0xf. These are
>    usually fields that were initial RAZ and turned to -1.
>
> So we can treat (a) and (b) as unsigned permanently and (c) as as
> signed,
>
> [1] https://lkml.org/lkml/2015/11/19/549
>
> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

I do feel that it would be very useful to document that nature of
those fields in the ARM ARM. If it is the intention to expose
incremental functionality, the values should be documented as such,
e.g., AES[7:4] >= 1 means AES instructions supported, >= 2 means AES
and PMULL instructions supported. Without classifying the fields in
such a way, there is no way to be compatible with future extensions.
In this example, it would perhaps be safer to assume no such
instructions are supported for values outside of the documented range.

-- 
Ard.


> ---
>  arch/arm/include/asm/smp_plat.h |    4 ++--
>  arch/arm/kernel/setup.c         |   34 ++++++++++++++++++++--------------
>  arch/arm/kernel/thumbee.c       |    4 +---
>  arch/arm/mm/mmu.c               |    2 +-
>  4 files changed, 24 insertions(+), 20 deletions(-)
>
> diff --git a/arch/arm/include/asm/smp_plat.h b/arch/arm/include/asm/smp_plat.h
> index f908071..03bbe02 100644
> --- a/arch/arm/include/asm/smp_plat.h
> +++ b/arch/arm/include/asm/smp_plat.h
> @@ -49,7 +49,7 @@ static inline int tlb_ops_need_broadcast(void)
>         if (!is_smp())
>                 return 0;
>
> -       return ((read_cpuid_ext(CPUID_EXT_MMFR3) >> 12) & 0xf) < 2;
> +       return cpuid_feature_extract_unsigned(CPUID_EXT_MMFR3, 12) < 2;
>  }
>  #endif
>
> @@ -61,7 +61,7 @@ static inline int cache_ops_need_broadcast(void)
>         if (!is_smp())
>                 return 0;
>
> -       return ((read_cpuid_ext(CPUID_EXT_MMFR3) >> 12) & 0xf) < 1;
> +       return cpuid_feature_extract_unsigned(CPUID_EXT_MMFR3, 12) < 1;
>  }
>  #endif
>
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index fde041b..e696553 100644
> --- a/arch/arm/kernel/setup.c
> +++ b/arch/arm/kernel/setup.c
> @@ -257,11 +257,15 @@ static int __get_cpu_architecture(void)
>                 /* Revised CPUID format. Read the Memory Model Feature
>                  * Register 0 and check for VMSAv7 or PMSAv7 */
>                 unsigned int mmfr0 = read_cpuid_ext(CPUID_EXT_MMFR0);
> -               if ((mmfr0 & 0x0000000f) >= 0x00000003 ||
> -                   (mmfr0 & 0x000000f0) >= 0x00000030)
> +               unsigned int block;
> +#ifdef CONFIG_MMU
> +               block = cpuid_feature_extract_unsigned_field(mmfr0, 0);
> +#else
> +               block = cpuid_feature_extract_unsigned_field(mmfr0, 4);
> +#endif
> +               if (mmfr0 >= 3)
>                         cpu_arch = CPU_ARCH_ARMv7;
> -               else if ((mmfr0 & 0x0000000f) == 0x00000002 ||
> -                        (mmfr0 & 0x000000f0) == 0x00000020)
> +               else if (mmfr0 == 2)
>                         cpu_arch = CPU_ARCH_ARMv6;
>                 else
>                         cpu_arch = CPU_ARCH_UNKNOWN;
> @@ -446,41 +450,41 @@ static inline void patch_aeabi_idiv(void) { }
>
>  static void __init cpuid_init_hwcaps(void)
>  {
> -       int block;
> +       unsigned int block;
>         u32 isar5;
>
>         if (cpu_architecture() < CPU_ARCH_ARMv7)
>                 return;
>
> -       block = cpuid_feature_extract(CPUID_EXT_ISAR0, 24);
> +       block = cpuid_feature_extract_unsigned(CPUID_EXT_ISAR0, 24);
>         if (block >= 2)
>                 elf_hwcap |= HWCAP_IDIVA;
>         if (block >= 1)
>                 elf_hwcap |= HWCAP_IDIVT;
>
>         /* LPAE implies atomic ldrd/strd instructions */
> -       block = cpuid_feature_extract(CPUID_EXT_MMFR0, 0);
> +       block = cpuid_feature_extract_unsigned(CPUID_EXT_MMFR0, 0);
>         if (block >= 5)
>                 elf_hwcap |= HWCAP_LPAE;
>
>         /* check for supported v8 Crypto instructions */
>         isar5 = read_cpuid_ext(CPUID_EXT_ISAR5);
>
> -       block = cpuid_feature_extract_field(isar5, 4);
> +       block = cpuid_feature_extract_unsigned_field(isar5, 4);
>         if (block >= 2)
>                 elf_hwcap2 |= HWCAP2_PMULL;
>         if (block >= 1)
>                 elf_hwcap2 |= HWCAP2_AES;
>
> -       block = cpuid_feature_extract_field(isar5, 8);
> +       block = cpuid_feature_extract_unsigned_field(isar5, 8);
>         if (block >= 1)
>                 elf_hwcap2 |= HWCAP2_SHA1;
>
> -       block = cpuid_feature_extract_field(isar5, 12);
> +       block = cpuid_feature_extract_unsigned_field(isar5, 12);
>         if (block >= 1)
>                 elf_hwcap2 |= HWCAP2_SHA2;
>
> -       block = cpuid_feature_extract_field(isar5, 16);
> +       block = cpuid_feature_extract_unsigned_field(isar5, 16);
>         if (block >= 1)
>                 elf_hwcap2 |= HWCAP2_CRC32;
>  }
> @@ -488,6 +492,7 @@ static void __init cpuid_init_hwcaps(void)
>  static void __init elf_hwcap_fixup(void)
>  {
>         unsigned id = read_cpuid_id();
> +       unsigned int block;
>
>         /*
>          * HWCAP_TLS is available only on 1136 r1p0 and later,
> @@ -508,9 +513,10 @@ static void __init elf_hwcap_fixup(void)
>          * avoid advertising SWP; it may not be atomic with
>          * multiprocessing cores.
>          */
> -       if (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) > 1 ||
> -           (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) == 1 &&
> -            cpuid_feature_extract(CPUID_EXT_ISAR4, 20) >= 3))
> +       block = cpuid_feature_extract_unsigned(CPUID_EXT_ISAR3, 12);
> +
> +       if (block > 1 || (block == 1 &&
> +           cpuid_feature_extract_unsigned(CPUID_EXT_ISAR4, 20) >= 3))
>                 elf_hwcap &= ~HWCAP_SWP;
>  }
>
> diff --git a/arch/arm/kernel/thumbee.c b/arch/arm/kernel/thumbee.c
> index 8ff8dbf..b5cac80 100644
> --- a/arch/arm/kernel/thumbee.c
> +++ b/arch/arm/kernel/thumbee.c
> @@ -62,14 +62,12 @@ static struct notifier_block thumbee_notifier_block = {
>
>  static int __init thumbee_init(void)
>  {
> -       unsigned long pfr0;
>         unsigned int cpu_arch = cpu_architecture();
>
>         if (cpu_arch < CPU_ARCH_ARMv7)
>                 return 0;
>
> -       pfr0 = read_cpuid_ext(CPUID_EXT_PFR0);
> -       if ((pfr0 & 0x0000f000) != 0x00001000)
> +       if (cpuid_feature_extract_unsigned(CPUID_EXT_PFR0, 12) != 1)
>                 return 0;
>
>         pr_info("ThumbEE CPU extension supported.\n");
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index 434d76f..06723a9 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -572,7 +572,7 @@ static void __init build_mem_type_table(void)
>          * in the Short-descriptor translation table format descriptors.
>          */
>         if (cpu_arch == CPU_ARCH_ARMv7 &&
> -               (read_cpuid_ext(CPUID_EXT_MMFR0) & 0xF) >= 4) {
> +               (cpuid_feature_extract_unsigned(CPUID_EXT_MMFR0, 0) >= 4)) {
>                 user_pmd_table |= PMD_PXNTABLE;
>         }
>  #endif
> --
> 1.7.9.5
>

[PATCH 0/4] Update cpu feature extraction

[Vladimir Murzin]

On 26/01/16 09:23, Vladimir Murzin wrote:
> Hi,
> 
> This has been started as a fix in cpu feature extractor, but Suzuki suggested
> syncing-up the whole cpu feature handling with the recent updates on arm64
> side [1,2].
> 
> I've kept fixes separately, so they can go as the are in case there is concern
> on updating cpu feature handling.
> 
> [1] http://comments.gmane.org/gmane.linux.ports.arm.kernel/455568
> [2] https://lkml.org/lkml/2015/11/18/570
> 

Russell, is it OK for patch tracker?

Cheers
Vladimir

> Thanks!
> 
> Vladimir Murzin (4):
>   ARM: fix demoting HWCAP_SWP
>   ARM: fix cpu feature extracting helper
>   ARM: introduce cpu feature helper for unsigned values
>   ARM: use proper helper while extracting cpu features
> 
>  arch/arm/include/asm/cputype.h  |   16 +++++++++++++---
>  arch/arm/include/asm/smp_plat.h |    4 ++--
>  arch/arm/kernel/setup.c         |   34 ++++++++++++++++++++--------------
>  arch/arm/kernel/thumbee.c       |    4 +---
>  arch/arm/mm/mmu.c               |    2 +-
>  5 files changed, 37 insertions(+), 23 deletions(-)
> 

[PATCH 0/4] Update cpu feature extraction

[Russell King - ARM Linux]

On Thu, Jan 28, 2016 at 11:13:10AM +0000, Vladimir Murzin wrote:
> On 26/01/16 09:23, Vladimir Murzin wrote:
> > Hi,
> > 
> > This has been started as a fix in cpu feature extractor, but Suzuki suggested
> > syncing-up the whole cpu feature handling with the recent updates on arm64
> > side [1,2].
> > 
> > I've kept fixes separately, so they can go as the are in case there is concern
> > on updating cpu feature handling.
> > 
> > [1] http://comments.gmane.org/gmane.linux.ports.arm.kernel/455568
> > [2] https://lkml.org/lkml/2015/11/18/570
> > 
> 
> Russell, is it OK for patch tracker?

I'd really like to hear that someone has validated these changes or at
least someone in ARM Ltd such as Will or Catalin has reviewed them; I
remember the subject of whether certain fields are signed or unsigned
being almost a personal opinion - we used to treat all fields as
unsigned, but that was declared to be wrong, so we then went to treating
them all as signed fields... See:

commit b8c9592b4a6c93211c8163888a97880d608503b5
Author: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date:   Thu Mar 19 19:03:25 2015 +0100

    ARM: 8318/1: treat CPU feature register fields as signed quantities

    The various CPU feature registers consist of 4-bit blocks that
    represent signed quantities, whose positive values represent
    incremental features, and whose negative values are reserved.

    To improve forward compatibility, update the feature detection
    code to take possible future higher values into account, but
    ignore negative values.

    Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
    Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

For instance:

-       sync_prim = ((read_cpuid_ext(CPUID_EXT_ISAR3) >> 8) & 0xf0) |
-                   ((read_cpuid_ext(CPUID_EXT_ISAR4) >> 20) & 0x0f);
-       if (sync_prim >= 0x13)
+       if (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) > 1 ||
+           (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) == 1 &&
+            cpuid_feature_extract(CPUID_EXT_ISAR3, 20) >= 3))
                elf_hwcap &= ~HWCAP_SWP;

(let's ignore the ISAR4 vs ISAR3 problem).  What if ISAR4 20:23 have
bit 23 set?  In the original code, that would be treated as being ">= 3"
but in the new code, that's less than zero, so would fail the test.

I think we had much the same questions back in March 2015 when this was
last discussed, when I raised the issue of there being a documentation
bug in that the documentation doesn't make it clear how reserved 4-bit
CPU ID fields should be intepreted.

What I'd like to see is some kind of positive concensus on this (and
a doc update); what I don't want to do is to apply these patches and
then get another round of patches converting some of them back to
signed tests, and then later another set of patches doing the reverse,
because that seems to be what's now happening.

-- 
RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

[PATCH 0/4] Update cpu feature extraction

[Ard Biesheuvel]

On 28 January 2016 at 18:01, Russell King - ARM Linux
<linux@arm.linux.org.uk> wrote:
> On Thu, Jan 28, 2016 at 11:13:10AM +0000, Vladimir Murzin wrote:
>> On 26/01/16 09:23, Vladimir Murzin wrote:
>> > Hi,
>> >
>> > This has been started as a fix in cpu feature extractor, but Suzuki suggested
>> > syncing-up the whole cpu feature handling with the recent updates on arm64
>> > side [1,2].
>> >
>> > I've kept fixes separately, so they can go as the are in case there is concern
>> > on updating cpu feature handling.
>> >
>> > [1] http://comments.gmane.org/gmane.linux.ports.arm.kernel/455568
>> > [2] https://lkml.org/lkml/2015/11/18/570
>> >
>>
>> Russell, is it OK for patch tracker?
>
> I'd really like to hear that someone has validated these changes or at
> least someone in ARM Ltd such as Will or Catalin has reviewed them; I
> remember the subject of whether certain fields are signed or unsigned
> being almost a personal opinion - we used to treat all fields as
> unsigned, but that was declared to be wrong, so we then went to treating
> them all as signed fields... See:
>
> commit b8c9592b4a6c93211c8163888a97880d608503b5
> Author: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Date:   Thu Mar 19 19:03:25 2015 +0100
>
>     ARM: 8318/1: treat CPU feature register fields as signed quantities
>
>     The various CPU feature registers consist of 4-bit blocks that
>     represent signed quantities, whose positive values represent
>     incremental features, and whose negative values are reserved.
>
>     To improve forward compatibility, update the feature detection
>     code to take possible future higher values into account, but
>     ignore negative values.
>
>     Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>     Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
>
> For instance:
>
> -       sync_prim = ((read_cpuid_ext(CPUID_EXT_ISAR3) >> 8) & 0xf0) |
> -                   ((read_cpuid_ext(CPUID_EXT_ISAR4) >> 20) & 0x0f);
> -       if (sync_prim >= 0x13)
> +       if (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) > 1 ||
> +           (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) == 1 &&
> +            cpuid_feature_extract(CPUID_EXT_ISAR3, 20) >= 3))
>                 elf_hwcap &= ~HWCAP_SWP;
>
> (let's ignore the ISAR4 vs ISAR3 problem).  What if ISAR4 20:23 have
> bit 23 set?  In the original code, that would be treated as being ">= 3"
> but in the new code, that's less than zero, so would fail the test.
>
> I think we had much the same questions back in March 2015 when this was
> last discussed, when I raised the issue of there being a documentation
> bug in that the documentation doesn't make it clear how reserved 4-bit
> CPU ID fields should be intepreted.
>
> What I'd like to see is some kind of positive concensus on this (and
> a doc update); what I don't want to do is to apply these patches and
> then get another round of patches converting some of them back to
> signed tests, and then later another set of patches doing the reverse,
> because that seems to be what's now happening.
>

Indeed. As I commented to one of the other patches, having any kind of
less-than/greater-than relation does not make any sense if the ARM ARM
defines '0 means A, 1 means B, all other values reserved' since the
whole point of the comparisons is to infer A or B (or both) from other
values than 0 or 1. My understanding at the time was that these fields
are signed 4-bit quantities, and so each positive value n implies all
of [0, n-1] as well.

If this turns out not to be the case, we should simply not infer the
presence of features based on
reserved-yet-greater-than-some-documented values, and back out my
changes to that effect as well.

-- 
Ard.

[PATCH 0/4] Update cpu feature extraction

[Vladimir Murzin]

On 28/01/16 17:01, Russell King - ARM Linux wrote:
> On Thu, Jan 28, 2016 at 11:13:10AM +0000, Vladimir Murzin wrote:
>> On 26/01/16 09:23, Vladimir Murzin wrote:
>>> Hi,
>>>
>>> This has been started as a fix in cpu feature extractor, but Suzuki suggested
>>> syncing-up the whole cpu feature handling with the recent updates on arm64
>>> side [1,2].
>>>
>>> I've kept fixes separately, so they can go as the are in case there is concern
>>> on updating cpu feature handling.
>>>
>>> [1] http://comments.gmane.org/gmane.linux.ports.arm.kernel/455568
>>> [2] https://lkml.org/lkml/2015/11/18/570
>>>
>>
>> Russell, is it OK for patch tracker?
> 
> I'd really like to hear that someone has validated these changes or at
> least someone in ARM Ltd such as Will or Catalin has reviewed them; I
> remember the subject of whether certain fields are signed or unsigned
> being almost a personal opinion - we used to treat all fields as
> unsigned, but that was declared to be wrong, so we then went to treating
> them all as signed fields... See:
> 
> commit b8c9592b4a6c93211c8163888a97880d608503b5
> Author: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Date:   Thu Mar 19 19:03:25 2015 +0100
> 
>     ARM: 8318/1: treat CPU feature register fields as signed quantities
> 
>     The various CPU feature registers consist of 4-bit blocks that
>     represent signed quantities, whose positive values represent
>     incremental features, and whose negative values are reserved.
> 
>     To improve forward compatibility, update the feature detection
>     code to take possible future higher values into account, but
>     ignore negative values.
> 
>     Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>     Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
> 
> For instance:
> 
> -       sync_prim = ((read_cpuid_ext(CPUID_EXT_ISAR3) >> 8) & 0xf0) |
> -                   ((read_cpuid_ext(CPUID_EXT_ISAR4) >> 20) & 0x0f);
> -       if (sync_prim >= 0x13)
> +       if (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) > 1 ||
> +           (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) == 1 &&
> +            cpuid_feature_extract(CPUID_EXT_ISAR3, 20) >= 3))
>                 elf_hwcap &= ~HWCAP_SWP;
> 
> (let's ignore the ISAR4 vs ISAR3 problem).  What if ISAR4 20:23 have
> bit 23 set?  In the original code, that would be treated as being ">= 3"
> but in the new code, that's less than zero, so would fail the test.
> 
> I think we had much the same questions back in March 2015 when this was
> last discussed, when I raised the issue of there being a documentation
> bug in that the documentation doesn't make it clear how reserved 4-bit
> CPU ID fields should be intepreted.
> 
> What I'd like to see is some kind of positive concensus on this (and
> a doc update); what I don't want to do is to apply these patches and
> then get another round of patches converting some of them back to
> signed tests, and then later another set of patches doing the reverse,
> because that seems to be what's now happening.
> 

It is fair point. Since this topic is quite fuzzy and discussion can
take some time I'd be happy if only fixes (the first two patches) can
find their way to mainline independent of the rest of the series.

Is it OK for patches 1/4 and 2/4 to go in patch tracker?

Thanks
Vladimir

[PATCH 0/4] Update cpu feature extraction

[Vladimir Murzin]

On 29/01/16 10:36, Vladimir Murzin wrote:
> On 28/01/16 17:01, Russell King - ARM Linux wrote:
>> On Thu, Jan 28, 2016 at 11:13:10AM +0000, Vladimir Murzin wrote:
>>> On 26/01/16 09:23, Vladimir Murzin wrote:
>>>> Hi,
>>>>
>>>> This has been started as a fix in cpu feature extractor, but Suzuki suggested
>>>> syncing-up the whole cpu feature handling with the recent updates on arm64
>>>> side [1,2].
>>>>
>>>> I've kept fixes separately, so they can go as the are in case there is concern
>>>> on updating cpu feature handling.
>>>>
>>>> [1] http://comments.gmane.org/gmane.linux.ports.arm.kernel/455568
>>>> [2] https://lkml.org/lkml/2015/11/18/570
>>>>
>>>
>>> Russell, is it OK for patch tracker?
>>
>> I'd really like to hear that someone has validated these changes or at
>> least someone in ARM Ltd such as Will or Catalin has reviewed them; I
>> remember the subject of whether certain fields are signed or unsigned
>> being almost a personal opinion - we used to treat all fields as
>> unsigned, but that was declared to be wrong, so we then went to treating
>> them all as signed fields... See:
>>
>> commit b8c9592b4a6c93211c8163888a97880d608503b5
>> Author: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> Date:   Thu Mar 19 19:03:25 2015 +0100
>>
>>     ARM: 8318/1: treat CPU feature register fields as signed quantities
>>
>>     The various CPU feature registers consist of 4-bit blocks that
>>     represent signed quantities, whose positive values represent
>>     incremental features, and whose negative values are reserved.
>>
>>     To improve forward compatibility, update the feature detection
>>     code to take possible future higher values into account, but
>>     ignore negative values.
>>
>>     Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>>     Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
>>
>> For instance:
>>
>> -       sync_prim = ((read_cpuid_ext(CPUID_EXT_ISAR3) >> 8) & 0xf0) |
>> -                   ((read_cpuid_ext(CPUID_EXT_ISAR4) >> 20) & 0x0f);
>> -       if (sync_prim >= 0x13)
>> +       if (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) > 1 ||
>> +           (cpuid_feature_extract(CPUID_EXT_ISAR3, 12) == 1 &&
>> +            cpuid_feature_extract(CPUID_EXT_ISAR3, 20) >= 3))
>>                 elf_hwcap &= ~HWCAP_SWP;
>>
>> (let's ignore the ISAR4 vs ISAR3 problem).  What if ISAR4 20:23 have
>> bit 23 set?  In the original code, that would be treated as being ">= 3"
>> but in the new code, that's less than zero, so would fail the test.
>>
>> I think we had much the same questions back in March 2015 when this was
>> last discussed, when I raised the issue of there being a documentation
>> bug in that the documentation doesn't make it clear how reserved 4-bit
>> CPU ID fields should be intepreted.
>>
>> What I'd like to see is some kind of positive concensus on this (and
>> a doc update); what I don't want to do is to apply these patches and
>> then get another round of patches converting some of them back to
>> signed tests, and then later another set of patches doing the reverse,
>> because that seems to be what's now happening.
>>
> 
> It is fair point. Since this topic is quite fuzzy and discussion can
> take some time I'd be happy if only fixes (the first two patches) can
> find their way to mainline independent of the rest of the series.
> 
> Is it OK for patches 1/4 and 2/4 to go in patch tracker?
> 

I've just uploaded patches 1/4 and 2/4 to patch tracker with assumption
they are OK, please, let me know in case it's wrong.

Cheers
Vladimir

> Thanks
> Vladimir
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
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> 
> 
>