From: Will Deacon <w...@kernel.org> [ 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.ran...@codeaurora.org> Cc: Stephen Boyd <swb...@chromium.org> Cc: Catalin Marinas <catalin.mari...@arm.com> Cc: Mark Rutland <mark.rutl...@arm.com> Reviewed-by: Suzuki K Poulose <suzuki.poul...@arm.com> Acked-by: Marc Zyngier <m...@kernel.org> Link: https://lore.kernel.org/r/20201106114952.10032-1-w...@kernel.org Signed-off-by: Will Deacon <w...@kernel.org> Signed-off-by: Sasha Levin <sas...@kernel.org> --- 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 10d3048dec7c2..ccae05da98a7f 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -262,6 +262,8 @@ 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 10190c4b16dc4..7d7cfa128b71b 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -511,14 +511,13 @@ 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
