[PATCH 4.4 071/113] arm64: cpufeature: Track 32bit EL0 support

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Suzuki K Poulose <suzuki.poulose@xxxxxxx>

commit 042446a31e3803d81c7e618dd80928dc3dce70c5 upstream.

Add cpu_hwcap bit for keeping track of the support for 32bit EL0.

Tested-by: Yury Norov <ynorov@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/arm64/include/asm/cpufeature.h |    8 +++++++-
 arch/arm64/include/asm/sysreg.h     |    1 +
 arch/arm64/kernel/cpufeature.c      |    8 ++++++++
 3 files changed, 16 insertions(+), 1 deletion(-)

--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -31,8 +31,9 @@
 #define ARM64_WORKAROUND_CAVIUM_23154		6
 #define ARM64_WORKAROUND_834220			7
 #define ARM64_WORKAROUND_CAVIUM_27456		8
+#define ARM64_HAS_32BIT_EL0			9
 
-#define ARM64_NCAPS				9
+#define ARM64_NCAPS				10
 
 #ifndef __ASSEMBLY__
 
@@ -180,6 +181,11 @@ static inline bool cpu_supports_mixed_en
 	return id_aa64mmfr0_mixed_endian_el0(read_cpuid(ID_AA64MMFR0_EL1));
 }
 
+static inline bool system_supports_32bit_el0(void)
+{
+	return cpus_have_cap(ARM64_HAS_32BIT_EL0);
+}
+
 static inline bool system_supports_mixed_endian_el0(void)
 {
 	return id_aa64mmfr0_mixed_endian_el0(read_system_reg(SYS_ID_AA64MMFR0_EL1));
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -109,6 +109,7 @@
 #define ID_AA64PFR0_ASIMD_SUPPORTED	0x0
 #define ID_AA64PFR0_EL1_64BIT_ONLY	0x1
 #define ID_AA64PFR0_EL0_64BIT_ONLY	0x1
+#define ID_AA64PFR0_EL0_32BIT_64BIT	0x2
 
 /* id_aa64mmfr0 */
 #define ID_AA64MMFR0_TGRAN4_SHIFT	28
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -653,6 +653,14 @@ static const struct arm64_cpu_capabiliti
 		.min_field_value = 2,
 	},
 #endif /* CONFIG_AS_LSE && CONFIG_ARM64_LSE_ATOMICS */
+	{
+		.desc = "32-bit EL0 Support",
+		.capability = ARM64_HAS_32BIT_EL0,
+		.matches = has_cpuid_feature,
+		.sys_reg = SYS_ID_AA64PFR0_EL1,
+		.field_pos = ID_AA64PFR0_EL0_SHIFT,
+		.min_field_value = ID_AA64PFR0_EL0_32BIT_64BIT,
+	},
 	{},
 };