When triggering a CPU hotplug scenario, we reparse the CPU feature with SCOPE_LOCAL_CPU, for which we use __read_sysreg_by_encoding() to get the HW value for this CPU. As it turns out, we're missing the handling for ID_AA64MMFR4_EL1, and trigger a BUG(). Funnily enough, Marek isn't completely happy about that. Add the damn register to the list. Fixes: 805bb61f8279 ("arm64: cpufeature: Add ID_AA64MMFR4_EL1 handling") Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx> --- arch/arm64/kernel/cpufeature.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 0f29ac43c7a2..2f8958f27e9e 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1456,6 +1456,7 @@ u64 __read_sysreg_by_encoding(u32 sys_id) read_sysreg_case(SYS_ID_AA64MMFR1_EL1); read_sysreg_case(SYS_ID_AA64MMFR2_EL1); read_sysreg_case(SYS_ID_AA64MMFR3_EL1); + read_sysreg_case(SYS_ID_AA64MMFR4_EL1); read_sysreg_case(SYS_ID_AA64ISAR0_EL1); read_sysreg_case(SYS_ID_AA64ISAR1_EL1); read_sysreg_case(SYS_ID_AA64ISAR2_EL1); -- 2.39.2