[PATCH v4 23/36] x86/bugs: Add attack vector controls for mmio

[David Kaplan]

Use attack vectors controls to determine if mmio mitigation is required.

Signed-off-by: David Kaplan <david.kaplan@xxxxxxx>
---
 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 56d3bf343d1f..ba7c2a1ea98f 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -595,15 +595,21 @@ static const char * const mmio_strings[] = {
 static void __init mmio_select_mitigation(void)
 {
 	if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA) ||
-	     boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN) ||
-	     cpu_mitigations_off()) {
+	     boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN)) {
 		mmio_mitigation = MMIO_MITIGATION_OFF;
 		return;
 	}
 
 	/* Microcode will be checked in mmio_update_mitigation(). */
-	if (mmio_mitigation == MMIO_MITIGATION_AUTO)
-		mmio_mitigation = MMIO_MITIGATION_VERW;
+	if (mmio_mitigation == MMIO_MITIGATION_AUTO) {
+		if (should_mitigate_vuln(X86_BUG_MMIO_STALE_DATA))
+			mmio_mitigation = MMIO_MITIGATION_VERW;
+		else
+			mmio_mitigation = MMIO_MITIGATION_OFF;
+	}
+
+	if (mmio_mitigation == MMIO_MITIGATION_OFF)
+		return;
 
 	/*
 	 * Enable CPU buffer clear mitigation for host and VMM, if also affected
@@ -615,7 +621,7 @@ static void __init mmio_select_mitigation(void)
 
 static void __init mmio_update_mitigation(void)
 {
-	if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA) || cpu_mitigations_off())
+	if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
 		return;
 
 	if (verw_mitigation_selected)
@@ -665,7 +671,7 @@ static void __init mmio_apply_mitigation(void)
 	if (!(x86_arch_cap_msr & ARCH_CAP_FBSDP_NO))
 		static_branch_enable(&mds_idle_clear);
 
-	if (mmio_nosmt || cpu_mitigations_auto_nosmt())
+	if (mmio_nosmt || smt_mitigations == SMT_MITIGATIONS_ON)
 		cpu_smt_disable(false);
 }
 
-- 
2.34.1