From d9a065914dccce0bbd967cdef1ec21b4de545daf Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Mon, 22 Jan 2024 18:13:36 +0000 Subject: [PATCH] arm64: cpufeatures: Correctly handle signed values Although we've had signed values for some features such as PMUv3 and FP, the code that handles the comparaison with some limit has a couple of annoying issues: - the min_field_value is always unsigned, meaning that we cannot easily compare it with a negative value - it is not possible to have a range of values, let alone a range of negative values Fix this by: - adding an upper limit to the comparison, defaulting to all bits being set to the maximum positive value - ensuring that the signess of the min and max values are taken into account A ARM64_CPUID_FIELDS_NEG() macro is provided for signed features, but nothing is using it yet. Signed-off-by: Marc Zyngier Reviewed-by: Catalin Marinas Link: https://lore.kernel.org/r/20240122181344.258974-3-maz@kernel.org Signed-off-by: Oliver Upton --- arch/arm64/include/asm/cpufeature.h | 1 + arch/arm64/kernel/cpufeature.c | 65 +++++++++++++++++++++++++---- 2 files changed, 57 insertions(+), 9 deletions(-) diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 21c824edf8ce4..a98d95f3492bb 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -363,6 +363,7 @@ struct arm64_cpu_capabilities { u8 field_pos; u8 field_width; u8 min_field_value; + u8 max_field_value; u8 hwcap_type; bool sign; unsigned long hwcap; diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 8d1a634a403ee..92b1546f26223 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -140,12 +140,42 @@ void dump_cpu_features(void) pr_emerg("0x%*pb\n", ARM64_NCAPS, &system_cpucaps); } +#define __ARM64_MAX_POSITIVE(reg, field) \ + ((reg##_##field##_SIGNED ? \ + BIT(reg##_##field##_WIDTH - 1) : \ + BIT(reg##_##field##_WIDTH)) - 1) + +#define __ARM64_MIN_NEGATIVE(reg, field) BIT(reg##_##field##_WIDTH - 1) + +#define __ARM64_CPUID_FIELDS(reg, field, min_value, max_value) \ + .sys_reg = SYS_##reg, \ + .field_pos = reg##_##field##_SHIFT, \ + .field_width = reg##_##field##_WIDTH, \ + .sign = reg##_##field##_SIGNED, \ + .min_field_value = min_value, \ + .max_field_value = max_value, + +/* + * ARM64_CPUID_FIELDS() encodes a field with a range from min_value to + * an implicit maximum that depends on the sign-ess of the field. + * + * An unsigned field will be capped at all ones, while a signed field + * will be limited to the positive half only. + */ #define ARM64_CPUID_FIELDS(reg, field, min_value) \ - .sys_reg = SYS_##reg, \ - .field_pos = reg##_##field##_SHIFT, \ - .field_width = reg##_##field##_WIDTH, \ - .sign = reg##_##field##_SIGNED, \ - .min_field_value = reg##_##field##_##min_value, + __ARM64_CPUID_FIELDS(reg, field, \ + SYS_FIELD_VALUE(reg, field, min_value), \ + __ARM64_MAX_POSITIVE(reg, field)) + +/* + * ARM64_CPUID_FIELDS_NEG() encodes a field with a range from an + * implicit minimal value to max_value. This should be used when + * matching a non-implemented property. + */ +#define ARM64_CPUID_FIELDS_NEG(reg, field, max_value) \ + __ARM64_CPUID_FIELDS(reg, field, \ + __ARM64_MIN_NEGATIVE(reg, field), \ + SYS_FIELD_VALUE(reg, field, max_value)) #define __ARM64_FTR_BITS(SIGNED, VISIBLE, STRICT, TYPE, SHIFT, WIDTH, SAFE_VAL) \ { \ @@ -1451,11 +1481,28 @@ has_always(const struct arm64_cpu_capabilities *entry, int scope) static bool feature_matches(u64 reg, const struct arm64_cpu_capabilities *entry) { - int val = cpuid_feature_extract_field_width(reg, entry->field_pos, - entry->field_width, - entry->sign); + int val, min, max; + u64 tmp; + + val = cpuid_feature_extract_field_width(reg, entry->field_pos, + entry->field_width, + entry->sign); + + tmp = entry->min_field_value; + tmp <<= entry->field_pos; + + min = cpuid_feature_extract_field_width(tmp, entry->field_pos, + entry->field_width, + entry->sign); + + tmp = entry->max_field_value; + tmp <<= entry->field_pos; + + max = cpuid_feature_extract_field_width(tmp, entry->field_pos, + entry->field_width, + entry->sign); - return val >= entry->min_field_value; + return val >= min && val <= max; } static u64 -- 2.30.2