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

["tip-bot2 for David Kaplan" <tip-bot2@linutronix.de>]

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

Commit-ID:     71dc301c26e9503350cf4e736022cc1eb8e986a7
Gitweb:        https://git.kernel.org/tip/71dc301c26e9503350cf4e736022cc1eb8e986a7
Author:        David Kaplan <david.kaplan@amd.com>
AuthorDate:    Mon, 07 Jul 2025 13:33:04 -05:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 11 Jul 2025 17:56:40 +02:00

x86/bugs: Add attack vector controls for SRBDS

Use attack vector controls to determine if SRBDS mitigation is required.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250707183316.1349127-10-david.kaplan@amd.com
---
 arch/x86/kernel/cpu/bugs.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index a557d17..de0b5ef 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -870,13 +870,19 @@ void update_srbds_msr(void)
 
 static void __init srbds_select_mitigation(void)
 {
-	if (!boot_cpu_has_bug(X86_BUG_SRBDS) || cpu_mitigations_off()) {
+	if (!boot_cpu_has_bug(X86_BUG_SRBDS)) {
 		srbds_mitigation = SRBDS_MITIGATION_OFF;
 		return;
 	}
 
-	if (srbds_mitigation == SRBDS_MITIGATION_AUTO)
-		srbds_mitigation = SRBDS_MITIGATION_FULL;
+	if (srbds_mitigation == SRBDS_MITIGATION_AUTO) {
+		if (should_mitigate_vuln(X86_BUG_SRBDS))
+			srbds_mitigation = SRBDS_MITIGATION_FULL;
+		else {
+			srbds_mitigation = SRBDS_MITIGATION_OFF;
+			return;
+		}
+	}
 
 	/*
 	 * Check to see if this is one of the MDS_NO systems supporting TSX that