This is a note to let you know that I've just added the patch titled
arm64: errata: Fix handling of 1418040 with late CPU onlining
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm64-errata-fix-handling-of-1418040-with-late-cpu-o.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 40453dbe62f89e0ce89e8499486d5fb09868b7b8
Author: Will Deacon <will@xxxxxxxxxx>
Date: Fri Nov 6 11:14:26 2020 +0000
arm64: errata: Fix handling of 1418040 with late CPU onlining
[ 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>
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);
