• Mark Rutland's avatar
    arm64/cpufeature: check correct field width when updating sys_val · 638f863d
    Mark Rutland authored
    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 <mark.rutland@arm.com>
    Reviewed-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Will Deacon <will.deacon@arm.com>
    Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
cpufeature.h 7.03 KB