[PATCH v12 11/12] x86/vmscape: Resolve conflict between attack-vectors and vmscape=force
From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Date: 2026-06-23 17:35:37
Also in:
bpf, kvm, linux-doc, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit), x86 hardware vulnerabilities · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Peter Zijlstra, Josh Poimboeuf
vmscape=force option currently defaults to AUTO mitigation. This lets attack-vector controls to override the vmscape mitigation. Preventing the user from being able to force VMSCAPE mitigation. When vmscape mitigation is forced, allow it be deployed irrespective of attack vectors. Introduce VMSCAPE_MITIGATION_ON that wins over attack-vector controls. Tested-by: Jon Kohler <redacted> Reviewed-by: Nikolay Borisov <redacted> 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 1082ed1fb2e6..fbdb137720c4 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c@@ -3058,6 +3058,7 @@ 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,
@@ -3066,6 +3067,7 @@ 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",
@@ -3085,7 +3087,7 @@ 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 if (!strcmp(str, "auto")) { vmscape_mitigation = VMSCAPE_MITIGATION_AUTO; } else {
@@ -3117,6 +3119,7 @@ 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
@@ -3244,6 +3247,7 @@ 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