Commit 638f863d authored by Mark Rutland's avatar Mark Rutland Committed by Will Deacon

arm64/cpufeature: check correct field width when updating sys_val

When we're updating a register's sys_val, we use arm64_ftr_value() to
find the new field value. We use cpuid_feature_extract_field() to find
the new value, but this implicitly assumes a 4-bit field, so we may
extract more bits than we mean to for fields like CTR_EL0.L1ip.

This affects update_cpu_ftr_reg(), where we may extract erroneous values
for ftr_cur and ftr_new. Depending on the additional bits extracted in
either case, we may erroneously detect that the value is mismatched, and
we'll try to compute a new safe value.

Dependent on these extra bits and feature type, arm64_ftr_safe_value()
may pessimistically select the always-safe value, or may erroneously
choose either the extracted cur or new value as the safe option. The
extra bits will subsequently be masked out in arm64_ftr_set_value(), so
we may choose a higher value, yet write back a lower one.

Fix this by passing the width down explicitly in arm64_ftr_value(), so
we always extract the correct amount.
Signed-off-by: default avatarMark Rutland <>
Reviewed-by: default avatarSuzuki K Poulose <>
Cc: Catalin Marinas <>
Cc: Will Deacon <>
Signed-off-by: default avatarWill Deacon <>
parent d81bbe6d
......@@ -184,16 +184,22 @@ static inline u64 arm64_ftr_reg_user_value(const struct arm64_ftr_reg *reg)
static inline int __attribute_const__
cpuid_feature_extract_field(u64 features, int field, bool sign)
cpuid_feature_extract_field_width(u64 features, int field, int width, bool sign)
return (sign) ?
cpuid_feature_extract_signed_field(features, field) :
cpuid_feature_extract_unsigned_field(features, field);
cpuid_feature_extract_signed_field_width(features, field, width) :
cpuid_feature_extract_unsigned_field_width(features, field, width);
static inline int __attribute_const__
cpuid_feature_extract_field(u64 features, int field, bool sign)
return cpuid_feature_extract_field_width(features, field, 4, sign);
static inline s64 arm64_ftr_value(const struct arm64_ftr_bits *ftrp, u64 val)
return (s64)cpuid_feature_extract_field(val, ftrp->shift, ftrp->sign);
return (s64)cpuid_feature_extract_field_width(val, ftrp->shift, ftrp->width, ftrp->sign);
static inline bool id_aa64mmfr0_mixed_endian_el0(u64 mmfr0)
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