linux-kernel - [PATCH 9/9] x86/entry, cpumask: Provide non-instrumented variant of cpu_is

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Message-ID: <20200603114052.300804240@infradead.org>
Date:   Wed, 03 Jun 2020 13:40:23 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     tglx@...utronix.de
Cc:     x86@...nel.org, elver@...gle.com, paulmck@...nel.org,
        kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org,
        peterz@...radead.org, will@...nel.org, dvyukov@...gle.com,
        glider@...gle.com, andreyknvl@...gle.com
Subject: [PATCH 9/9] x86/entry, cpumask: Provide non-instrumented variant of cpu_is_offline()

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@...radead.org>
---
 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						\