From: Will Deacon <will@xxxxxxxxxx> [ Upstream commit f969f03888b9438fdb227b6460d99ede5737326d ] In a surprising turn of events, it transpires that CPU capabilities configured as ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE are never set as the result of late-onlining. Therefore our handling of erratum 1418040 does not get activated if it is not required by any of the boot CPUs, even though we allow late-onlining of an affected CPU. In order to get things working again, replace the cpus_have_const_cap() invocation with an explicit check for the current CPU using this_cpu_has_cap(). Cc: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx> Cc: Stephen Boyd <swboyd@xxxxxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Mark Rutland <mark.rutland@xxxxxxx> Reviewed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx> Acked-by: Marc Zyngier <maz@xxxxxxxxxx> Link: https://lore.kernel.org/r/20201106114952.10032-1-will@xxxxxxxxxx Signed-off-by: Will Deacon <will@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- arch/arm64/include/asm/cpufeature.h | 2 ++ arch/arm64/kernel/process.c | 5 ++--- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 89b4f0142c287..a986ecd0b0074 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -268,6 +268,8 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0; /* * CPU feature detected at boot time based on feature of one or more CPUs. * All possible conflicts for a late CPU are ignored. + * NOTE: this means that a late CPU with the feature will *not* cause the + * capability to be advertised by cpus_have_*cap()! */ #define ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE \ (ARM64_CPUCAP_SCOPE_LOCAL_CPU | \ diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index f1804496b9350..2da5f3f9d345f 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -526,14 +526,13 @@ static void erratum_1418040_thread_switch(struct task_struct *prev, bool prev32, next32; u64 val; - if (!(IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040) && - cpus_have_const_cap(ARM64_WORKAROUND_1418040))) + if (!IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040)) return; prev32 = is_compat_thread(task_thread_info(prev)); next32 = is_compat_thread(task_thread_info(next)); - if (prev32 == next32) + if (prev32 == next32 || !this_cpu_has_cap(ARM64_WORKAROUND_1418040)) return; val = read_sysreg(cntkctl_el1); -- 2.27.0
