arm64: cpufeature: Fix CLRBHB and BC detection

ClearBHB support is indicated by the CLRBHB field in ID_AA64ISAR2_EL1.
Following some refactoring the kernel incorrectly checks the BC field
instead. Fix the detection to use the right field.

(Note: The original ClearBHB support had it as FTR_HIGHER_SAFE, but this
patch uses FTR_LOWER_SAFE, which seems more correct.)

Also fix the detection of BC (hinted conditional branches) to use
FTR_LOWER_SAFE, so that it is not reported on mismatched systems.

Fixes: 356137e68a9f ("arm64/sysreg: Make BHB clear feature defines match the architecture")
Fixes: 8fcc8285c0e3 ("arm64/sysreg: Convert ID_AA64ISAR2_EL1 to automatic generation")
Cc: stable@vger.kernel.org
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230912133429.2606875-1-kristina.martsenko@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 96e5022..5bba393 100644 (file)
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -663,7 +663,7 @@ static inline bool supports_clearbhb(int scope)
                isar2 = read_sanitised_ftr_reg(SYS_ID_AA64ISAR2_EL1);
 
        return cpuid_feature_extract_unsigned_field(isar2,
-                                                   ID_AA64ISAR2_EL1_BC_SHIFT);
+                                                   ID_AA64ISAR2_EL1_CLRBHB_SHIFT);
 }
 
 const struct cpumask *system_32bit_el0_cpumask(void);

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index b018ae1..444a73c 100644 (file)
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -222,7 +222,8 @@ static const struct arm64_ftr_bits ftr_id_aa64isar1[] = {
 static const struct arm64_ftr_bits ftr_id_aa64isar2[] = {
        ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64ISAR2_EL1_CSSC_SHIFT, 4, 0),
        ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64ISAR2_EL1_RPRFM_SHIFT, 4, 0),
-       ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_HIGHER_SAFE, ID_AA64ISAR2_EL1_BC_SHIFT, 4, 0),
+       ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR2_EL1_CLRBHB_SHIFT, 4, 0),
+       ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR2_EL1_BC_SHIFT, 4, 0),
        ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR2_EL1_MOPS_SHIFT, 4, 0),
        ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_PTR_AUTH),
                       FTR_STRICT, FTR_EXACT, ID_AA64ISAR2_EL1_APA3_SHIFT, 4, 0),

diff --git a/arch/arm64/tools/sysreg b/arch/arm64/tools/sysreg
index 2517ef7..76ce150 100644 (file)
--- a/arch/arm64/tools/sysreg
+++ b/arch/arm64/tools/sysreg
@@ -1347,7 +1347,11 @@ UnsignedEnum     51:48   RPRFM
        0b0000  NI
        0b0001  IMP
 EndEnum
-Res0   47:28
+Res0   47:32
+UnsignedEnum   31:28   CLRBHB
+       0b0000  NI
+       0b0001  IMP
+EndEnum
 UnsignedEnum   27:24   PAC_frac
        0b0000  NI
        0b0001  IMP