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Message-ID: <20250509162839.3057217-13-david.kaplan@amd.com>
Date: Fri, 9 May 2025 11:28:31 -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 12/20] x86/bugs: Add attack vector controls for retbleed
Use attack vector controls to determine if retbleed mitigation is
required.
Disable SMT if cross-thread protection is desired and STIBP is not
available.
Signed-off-by: David Kaplan <david.kaplan@....com>
---
arch/x86/kernel/cpu/bugs.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index ad68130707c2..160dcaa18b04 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1251,7 +1251,7 @@ early_param("retbleed", retbleed_parse_cmdline);
static void __init retbleed_select_mitigation(void)
{
- if (!boot_cpu_has_bug(X86_BUG_RETBLEED) || cpu_mitigations_off()) {
+ if (!boot_cpu_has_bug(X86_BUG_RETBLEED)) {
retbleed_mitigation = RETBLEED_MITIGATION_NONE;
return;
}
@@ -1288,6 +1288,11 @@ static void __init retbleed_select_mitigation(void)
if (retbleed_mitigation != RETBLEED_MITIGATION_AUTO)
return;
+ if (!should_mitigate_vuln(X86_BUG_RETBLEED)) {
+ retbleed_mitigation = RETBLEED_MITIGATION_NONE;
+ return;
+ }
+
/* Intel mitigation selected in retbleed_update_mitigation() */
if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
@@ -1303,7 +1308,7 @@ static void __init retbleed_select_mitigation(void)
static void __init retbleed_update_mitigation(void)
{
- if (!boot_cpu_has_bug(X86_BUG_RETBLEED) || cpu_mitigations_off())
+ if (!boot_cpu_has_bug(X86_BUG_RETBLEED))
return;
if (retbleed_mitigation == RETBLEED_MITIGATION_NONE)
@@ -1401,7 +1406,7 @@ static void __init retbleed_apply_mitigation(void)
}
if (mitigate_smt && !boot_cpu_has(X86_FEATURE_STIBP) &&
- (retbleed_nosmt || cpu_mitigations_auto_nosmt()))
+ (retbleed_nosmt || smt_mitigations == SMT_MITIGATIONS_ON))
cpu_smt_disable(false);
}
--
2.34.1
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