Commit f969f038 authored Nov 06, 2020 by Will Deacon

arm64: errata: Fix handling of 1418040 with late CPU onlining



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@codeaurora.org>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201106114952.10032-1-will@kernel.org


Signed-off-by: Will Deacon <will@kernel.org>

parent 108aa503

arch/arm64/include/asm/cpufeature.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -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 \| \

arch/arm64/kernel/process.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -522,14 +522,13 @@ 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);