[PATCH v6 8/9] x86/vmscape: Fix conflicting attack-vector controls with =force

[Pawan Gupta <pawan.kumar.gupta@linux.intel.com>]

vmscape=force option currently defaults to AUTO mitigation. This is not
correct because attack-vector controls overrides a mitigation in AUTO mode.
This prevents a user from being able to force VMSCAPE mitigation when it
conflicts with attack-vector controls.

Kernel should deploy a forced mitigation irrespective of attack vectors.
Instead of AUTO, use VMSCAPE_MITIGATION_ON that wins over attack-vector
controls.

Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
---
 arch/x86/kernel/cpu/bugs.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 61c3b4ae131f39fd716a54ba46d255844b1bb609..58cd26e4f4c385a10230912666c02dbb05e71cba 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -3197,6 +3197,7 @@ static void __init srso_apply_mitigation(void)
 enum vmscape_mitigations {
 	VMSCAPE_MITIGATION_NONE,
 	VMSCAPE_MITIGATION_AUTO,
+	VMSCAPE_MITIGATION_ON,
 	VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER,
 	VMSCAPE_MITIGATION_IBPB_ON_VMEXIT,
 	VMSCAPE_MITIGATION_BHB_CLEAR_EXIT_TO_USER,
@@ -3205,6 +3206,7 @@ enum vmscape_mitigations {
 static const char * const vmscape_strings[] = {
 	[VMSCAPE_MITIGATION_NONE]			= "Vulnerable",
 	/* [VMSCAPE_MITIGATION_AUTO] */
+	/* [VMSCAPE_MITIGATION_ON] */
 	[VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER]		= "Mitigation: IBPB before exit to userspace",
 	[VMSCAPE_MITIGATION_IBPB_ON_VMEXIT]		= "Mitigation: IBPB on VMEXIT",
 	[VMSCAPE_MITIGATION_BHB_CLEAR_EXIT_TO_USER]	= "Mitigation: Clear BHB before exit to userspace",
@@ -3224,7 +3226,7 @@ static int __init vmscape_parse_cmdline(char *str)
 		vmscape_mitigation = VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER;
 	} else if (!strcmp(str, "force")) {
 		setup_force_cpu_bug(X86_BUG_VMSCAPE);
-		vmscape_mitigation = VMSCAPE_MITIGATION_AUTO;
+		vmscape_mitigation = VMSCAPE_MITIGATION_ON;
 	} else {
 		pr_err("Ignoring unknown vmscape=%s option.\n", str);
 	}
@@ -3254,6 +3256,7 @@ static void __init vmscape_select_mitigation(void)
 		break;
 
 	case VMSCAPE_MITIGATION_AUTO:
+	case VMSCAPE_MITIGATION_ON:
 		/*
 		 * CPUs with BHI_CTRL(ADL and newer) can avoid the IBPB and use BHB
 		 * clear sequence. These CPUs are only vulnerable to the BHI variant
@@ -3379,6 +3382,7 @@ void cpu_bugs_smt_update(void)
 	switch (vmscape_mitigation) {
 	case VMSCAPE_MITIGATION_NONE:
 	case VMSCAPE_MITIGATION_AUTO:
+	case VMSCAPE_MITIGATION_ON:
 		break;
 	case VMSCAPE_MITIGATION_IBPB_ON_VMEXIT:
 	case VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER:

-- 
2.34.1