linux-kernel - [PATCH v7 17/31] x86/bugs: Mark cpu_buf_vm

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Message-ID: <20251114150133.1056710-18-vschneid@redhat.com>
Date: Fri, 14 Nov 2025 16:01:19 +0100
From: Valentin Schneider <vschneid@...hat.com>
To: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	rcu@...r.kernel.org,
	x86@...nel.org,
	linux-arm-kernel@...ts.infradead.org,
	loongarch@...ts.linux.dev,
	linux-riscv@...ts.infradead.org,
	linux-arch@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
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	Daniel Wagner <dwagner@...e.de>,
	Petr Tesarik <ptesarik@...e.com>,
	Shrikanth Hegde <sshegde@...ux.ibm.com>
Subject: [PATCH v7 17/31] x86/bugs: Mark cpu_buf_vm_clear key as allowed in .noinstr

The static key is only ever updated in

  __init mmio_apply_mitigation

Mark it to let objtool know not to warn about it.

Signed-off-by: Valentin Schneider <vschneid@...hat.com>
---
 arch/x86/kernel/cpu/bugs.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index d7fa03bf51b45..a2d7dc4d2a4a3 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -196,8 +196,11 @@ DEFINE_STATIC_KEY_FALSE(switch_mm_cond_l1d_flush);
  * Controls CPU Fill buffer clear before VMenter. This is a subset of
  * X86_FEATURE_CLEAR_CPU_BUF, and should only be enabled when KVM-only
  * mitigation is required.
+ *
+ * NOINSTR: This static key is only updated during init, so it can't be
+ * a cause of post-init interference.
  */
-DEFINE_STATIC_KEY_FALSE(cpu_buf_vm_clear);
+DEFINE_STATIC_KEY_FALSE_NOINSTR(cpu_buf_vm_clear);
 EXPORT_SYMBOL_GPL(cpu_buf_vm_clear);
 
 #undef pr_fmt
-- 
2.51.0