[PATCH 9/9] x86/entry, cpumask: Provide non-instrumented variant of cpu_is_offline()

From: Peter Zijlstra
Date: Wed Jun 03 2020 - 07:42:53 EST


vmlinux.o: warning: objtool: exc_nmi()+0x12: call to cpumask_test_cpu.constprop.0() leaves .noinstr.text section
vmlinux.o: warning: objtool: mce_check_crashing_cpu()+0x12: call to cpumask_test_cpu.constprop.0()leaves .noinstr.text section

cpumask_test_cpu()
test_bit()
instrument_atomic_read()
arch_test_bit()

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/mce/core.c | 2 +-
arch/x86/kernel/nmi.c | 2 +-
include/linux/cpumask.h | 15 ++++++++++++++-
3 files changed, 16 insertions(+), 3 deletions(-)

--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1083,7 +1083,7 @@ static noinstr bool mce_check_crashing_c
{
unsigned int cpu = smp_processor_id();

- if (cpu_is_offline(cpu) ||
+ if (arch_cpu_is_offline(cpu) ||
(crashing_cpu != -1 && crashing_cpu != cpu)) {
u64 mcgstatus;

--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -478,7 +478,7 @@ static DEFINE_PER_CPU(unsigned long, nmi

DEFINE_IDTENTRY_NMI(exc_nmi)
{
- if (IS_ENABLED(CONFIG_SMP) && cpu_is_offline(smp_processor_id()))
+ if (IS_ENABLED(CONFIG_SMP) && arch_cpu_is_offline(smp_processor_id()))
return;

if (this_cpu_read(nmi_state) != NMI_NOT_RUNNING) {
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -888,7 +888,20 @@ static inline const struct cpumask *get_
return to_cpumask(p);
}

-#define cpu_is_offline(cpu) unlikely(!cpu_online(cpu))
+#if NR_CPUS > 1
+static __always_inline bool arch_cpu_online(int cpu)
+{
+ return arch_test_bit(cpu, cpumask_bits(cpu_online_mask));
+}
+#else
+static __always_inline bool arch_cpu_online(int cpu)
+{
+ return cpu == 0;
+}
+#endif
+
+#define arch_cpu_is_offline(cpu) unlikely(!arch_cpu_online(cpu))
+#define cpu_is_offline(cpu) unlikely(!cpu_online(cpu))

#if NR_CPUS <= BITS_PER_LONG
#define CPU_BITS_ALL \