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Subject[PATCH 06/16] x86/cpu: Clear VMX feature flag if VMX is not fully enabled
Date
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 | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/feature_control.c b/arch/x86/kernel/cpu/feature_control.c
index 57b928e64cf5..74c76159a046 100644
--- a/arch/x86/kernel/cpu/feature_control.c
+++ b/arch/x86/kernel/cpu/feature_control.c
@@ -7,13 +7,19 @@

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("x86/cpu: VMX disabled, IA32_FEATURE_CONTROL MSR unsupported\n");
+ clear_cpu_cap(c, X86_FEATURE_VMX);
+ }
return;
+ }

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

/*
* Ignore whatever value BIOS left in the MSR to avoid enabling random
@@ -23,8 +29,19 @@ void init_feature_control_msr(struct cpuinfo_x86 *c)

if (cpu_has(c, X86_FEATURE_VMX)) {
msr |= FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX;
- if (tboot_enabled())
+ if (tboot)
msr |= FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX;
}
wrmsrl(MSR_IA32_FEATURE_CONTROL, msr);
+
+update_caps:
+ if (!cpu_has(c, X86_FEATURE_VMX))
+ return;
+
+ if ((tboot && !(msr & FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX)) ||
+ (!tboot && !(msr & FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX))) {
+ pr_err_once("x86/cpu: VMX disabled by BIOS (TXT %s)\n",
+ tboot ? "enabled" : "disabled");
+ clear_cpu_cap(c, X86_FEATURE_VMX);
+ }
}
--
2.22.0
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