[PATCH v3 09/19] x86/cpu: Clear VMX feature flag if VMX is not fully enabled

Sean Christopherson
2019-11-19T03:13:45Z

Now that the IA32_FEATURE_CONTROL MSR is guaranteed to be configured and
locked, clear the VMX capability flag if the IA32_FEATURE_CONTROL MSR is
not supported or if BIOS disabled VMX, i.e. locked IA32_FEATURE_CONTROL
and did not set the appropriate VMX enable bit.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kernel/cpu/feature_control.c | 28 ++++++++++++++++++++++++---
1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/feature_control.c b/arch/x86/kernel/cpu/feature_control.c
index 33c9444dda52..2bd1a9e6021a 100644
--- a/arch/x86/kernel/cpu/feature_control.c
+++ b/arch/x86/kernel/cpu/feature_control.c
@@ -5,15 +5,26 @@
#include <asm/msr-index.h>
#include <asm/processor.h>

+#undef pr_fmt
+#define pr_fmt(fmt) "x86/cpu: " fmt
+
+#define FEAT_CTL_UNSUPPORTED_MSG "IA32_FEATURE_CONTROL MSR unsupported on VMX capable CPU, suspected hardware or hypervisor issue.\n"
+
void init_feature_control_msr(struct cpuinfo_x86 *c)
{
+ bool tboot = tboot_enabled();
u64 msr;

- if (rdmsrl_safe(MSR_IA32_FEATURE_CONTROL, &msr))
+ if (rdmsrl_safe(MSR_IA32_FEATURE_CONTROL, &msr)) {
+ if (cpu_has(c, X86_FEATURE_VMX)) {
+ pr_err_once(FEAT_CTL_UNSUPPORTED_MSG);
+ clear_cpu_cap(c, X86_FEATURE_VMX);
+ }
return;
+ }

if (msr & FEAT_CTL_LOCKED)
- return;
+ goto update_caps;

/*
* Ignore whatever value BIOS left in the MSR to avoid enabling random
@@ -28,8 +39,19 @@ void init_feature_control_msr(struct cpuinfo_x86 *c)
*/
if (cpu_has(c, X86_FEATURE_VMX) && IS_ENABLED(CONFIG_KVM)) {
msr |= FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX;
- if (tboot_enabled())
+ if (tboot)
msr |= FEAT_CTL_VMX_ENABLED_INSIDE_SMX;
}
wrmsrl(MSR_IA32_FEATURE_CONTROL, msr);
+
+update_caps:
+ if (!cpu_has(c, X86_FEATURE_VMX))
+ return;
+
+ if ((tboot && !(msr & FEAT_CTL_VMX_ENABLED_INSIDE_SMX)) ||
+ (!tboot && !(msr & FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX))) {
+ pr_err_once("VMX (%s TXT) disabled by BIOS\n",
+ tboot ? "inside" : "outside");
+ clear_cpu_cap(c, X86_FEATURE_VMX);
+ }
}
--
2.24.0