[PATCH v4 06/11] x86/vmscape: Move mitigation selection to a switch()

Pawan Gupta
2025-11-20T06:19:05Z

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.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
---
arch/x86/kernel/cpu/bugs.c | 22 ++++++++++++++++++----
1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 1e9b11198db0fe2483bd17b1327bcfd44a2c1dbf..233594ede19bf971c999f4d3cc0f6f213002c16c 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -3231,17 +3231,31 @@ 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_ON_VMEXIT:
+ 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;
}
}

--
2.34.1