[PATCH v7 05/10] x86/vmscape: Move mitigation selection to a switch()

[Pawan Gupta]

This ensures that all mitigation modes are explicitly handled, while
keeping the mitigation selection for each mode together. This also prepares
for adding BHB-clearing mitigation mode for VMSCAPE.

Reviewed-by: Nikolay Borisov <nik.borisov@xxxxxxxx>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
---
 arch/x86/kernel/cpu/bugs.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 47c020b80371..68e2df3e3bf5 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -3084,17 +3084,33 @@ early_param("vmscape", vmscape_parse_cmdline);
 
 static void __init vmscape_select_mitigation(void)
 {
-	if (!boot_cpu_has_bug(X86_BUG_VMSCAPE) ||
-	    !boot_cpu_has(X86_FEATURE_IBPB)) {
+	if (!boot_cpu_has_bug(X86_BUG_VMSCAPE)) {
 		vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
 		return;
 	}
 
-	if (vmscape_mitigation == VMSCAPE_MITIGATION_AUTO) {
-		if (should_mitigate_vuln(X86_BUG_VMSCAPE))
+	if ((vmscape_mitigation == VMSCAPE_MITIGATION_AUTO) &&
+	    !should_mitigate_vuln(X86_BUG_VMSCAPE))
+		vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
+
+	switch (vmscape_mitigation) {
+	case VMSCAPE_MITIGATION_NONE:
+		break;
+
+	case VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER:
+		if (!boot_cpu_has(X86_FEATURE_IBPB))
+			vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
+		break;
+
+	case VMSCAPE_MITIGATION_AUTO:
+		if (boot_cpu_has(X86_FEATURE_IBPB))
 			vmscape_mitigation = VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER;
 		else
 			vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
+		break;
+
+	default:
+		break;
 	}
 }
 

-- 
2.34.1