[v6] Attack vector controls (part 2)

[PATCH v6 16/21] x86/bugs: Add attack vector controls for L1TF

Posted by David Kaplan 2 months, 4 weeks ago

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@amd.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 2168e75bc1ac..ecfd7d728ac5 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2884,17 +2884,23 @@ 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

[tip: x86/bugs] x86/bugs: Add attack vector controls for L1TF

Posted by tip-bot2 for David Kaplan 2 months, 3 weeks ago

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     2f970a526975f4437bdc9a4ba550ecc7e66d861d
Gitweb:        https://git.kernel.org/tip/2f970a526975f4437bdc9a4ba550ecc7e66d861d
Author:        David Kaplan <david.kaplan@amd.com>
AuthorDate:    Mon, 07 Jul 2025 13:33:11 -05:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 11 Jul 2025 17:56:41 +02:00

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@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250707183316.1349127-17-david.kaplan@amd.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 94c72f4..2128623 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2995,17 +2995,23 @@ 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)