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Message-ID: <20250509162839.3057217-6-david.kaplan@amd.com>
Date: Fri, 9 May 2025 11:28:24 -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 05/20] x86/bugs: Add attack vector controls for MDS
Use attack vector controls to determine if MDS mitigation is required.
The global mitigations=off command now simply disables all attack vectors
so explicit checking of mitigations=off is no longer needed.
If cross-thread attack mitigations are required, disable SMT.
Signed-off-by: David Kaplan <david.kaplan@....com>
---
arch/x86/kernel/cpu/bugs.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 3dce7c3126ea..97d152c33e9e 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -419,13 +419,17 @@ static bool verw_clear_cpu_buf_mitigation_selected __ro_after_init;
static void __init mds_select_mitigation(void)
{
- if (!boot_cpu_has_bug(X86_BUG_MDS) || cpu_mitigations_off()) {
+ if (!boot_cpu_has_bug(X86_BUG_MDS)) {
mds_mitigation = MDS_MITIGATION_OFF;
return;
}
- if (mds_mitigation == MDS_MITIGATION_AUTO)
- mds_mitigation = MDS_MITIGATION_FULL;
+ if (mds_mitigation == MDS_MITIGATION_AUTO) {
+ if (should_mitigate_vuln(X86_BUG_MDS))
+ mds_mitigation = MDS_MITIGATION_FULL;
+ else
+ mds_mitigation = MDS_MITIGATION_OFF;
+ }
if (mds_mitigation == MDS_MITIGATION_OFF)
return;
@@ -435,7 +439,7 @@ static void __init mds_select_mitigation(void)
static void __init mds_update_mitigation(void)
{
- if (!boot_cpu_has_bug(X86_BUG_MDS) || cpu_mitigations_off())
+ if (!boot_cpu_has_bug(X86_BUG_MDS))
return;
/* If TAA, MMIO, or RFDS are being mitigated, MDS gets mitigated too. */
@@ -456,7 +460,7 @@ static void __init mds_apply_mitigation(void)
mds_mitigation == MDS_MITIGATION_VMWERV) {
setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
if (!boot_cpu_has(X86_BUG_MSBDS_ONLY) &&
- (mds_nosmt || cpu_mitigations_auto_nosmt()))
+ (mds_nosmt || smt_mitigations == SMT_MITIGATIONS_ON))
cpu_smt_disable(false);
}
}
--
2.34.1
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