[PATCH v6 17/29] x86/speculation/mds: Mark cpu_buf_idle_clear key as allowed in .noinstr
From: Valentin Schneider <vschneid@redhat.com>
Date: 2025-10-10 15:45:21
Also in:
linux-arch, linux-arm-kernel, linux-mm, linux-riscv, lkml, loongarch, rcu
Subsystem:
the rest, x86 architecture (32-bit and 64-bit), x86 hardware vulnerabilities · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Peter Zijlstra, Josh Poimboeuf
Later commits will cause objtool to warn about static keys being used in .noinstr sections in order to safely defer instruction patching IPIs targeted at NOHZ_FULL CPUs. cpu_buf_idle_clear is used in .noinstr code, and can be modified at runtime (SMT hotplug). Suppressing the text_poke_sync() IPI has little benefits for this key, as hotplug implies eventually going through takedown_cpu() -> stop_machine_cpuslocked() which is going to cause interference on all online CPUs anyway. Mark it to let objtool know not to warn about it. Signed-off-by: Valentin Schneider <vschneid@redhat.com> --- arch/x86/kernel/cpu/bugs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 36dcfc5105be9..3aca329a853b5 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c@@ -182,7 +182,7 @@ DEFINE_STATIC_KEY_FALSE(switch_vcpu_ibpb); EXPORT_SYMBOL_GPL(switch_vcpu_ibpb); /* Control CPU buffer clear before idling (halt, mwait) */ -DEFINE_STATIC_KEY_FALSE(cpu_buf_idle_clear); +DEFINE_STATIC_KEY_FALSE_NOINSTR(cpu_buf_idle_clear); EXPORT_SYMBOL_GPL(cpu_buf_idle_clear); /*
--
2.51.0