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Message-ID: <20250509162839.3057217-17-david.kaplan@amd.com>
Date: Fri, 9 May 2025 11:28:35 -0500
From: David Kaplan <david.kaplan@....com>
To: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>,
Peter Zijlstra <peterz@...radead.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, Ingo Molnar
<mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>,
<x86@...nel.org>, "H . Peter Anvin" <hpa@...or.com>
CC: <linux-kernel@...r.kernel.org>
Subject: [PATCH v5 16/20] x86/bugs: Add attack vector controls for L1TF
Use attack vector controls to determine if L1TF mitigation is required.
Disable SMT if cross-thread protection is desired.
Signed-off-by: David Kaplan <david.kaplan@....com>
---
arch/x86/kernel/cpu/bugs.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 6a4bc80be1e9..19a176369b22 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2697,17 +2697,23 @@ static void override_cache_bits(struct cpuinfo_x86 *c)
static void __init l1tf_select_mitigation(void)
{
- if (!boot_cpu_has_bug(X86_BUG_L1TF) || cpu_mitigations_off()) {
+ if (!boot_cpu_has_bug(X86_BUG_L1TF)) {
l1tf_mitigation = L1TF_MITIGATION_OFF;
return;
}
- if (l1tf_mitigation == L1TF_MITIGATION_AUTO) {
- if (cpu_mitigations_auto_nosmt())
- l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
- else
- l1tf_mitigation = L1TF_MITIGATION_FLUSH;
+ if (l1tf_mitigation != L1TF_MITIGATION_AUTO)
+ return;
+
+ if (!should_mitigate_vuln(X86_BUG_L1TF)) {
+ l1tf_mitigation = L1TF_MITIGATION_OFF;
+ return;
}
+
+ if (smt_mitigations == SMT_MITIGATIONS_ON)
+ l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
+ else
+ l1tf_mitigation = L1TF_MITIGATION_FLUSH;
}
static void __init l1tf_apply_mitigation(void)
--
2.34.1
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