[PATCH v4 03/19] KVM: VMX: Disable FRED if FRED consistency checks fail

[Xin Li (Intel)]

From: Xin Li <xin3.li@xxxxxxxxx>

Do not virtualize FRED if FRED consistency checks fail.

Either on broken hardware, or when run KVM on top of another hypervisor
before the underlying hypervisor implements nested FRED correctly.

Suggested-by: Chao Gao <chao.gao@xxxxxxxxx>
Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
Signed-off-by: Xin Li (Intel) <xin@xxxxxxxxx>
Tested-by: Shan Kang <shan.kang@xxxxxxxxx>
Reviewed-by: Chao Gao <chao.gao@xxxxxxxxx>
---

Change in v4:
* Call out the reason why not check FRED VM-exit controls in
  cpu_has_vmx_fred() (Chao Gao).
---
 arch/x86/kvm/vmx/capabilities.h | 11 +++++++++++
 arch/x86/kvm/vmx/vmx.c          |  3 +++
 2 files changed, 14 insertions(+)

diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
index b2aefee59395..b4f49a4690ca 100644
--- a/arch/x86/kvm/vmx/capabilities.h
+++ b/arch/x86/kvm/vmx/capabilities.h
@@ -400,6 +400,17 @@ static inline bool vmx_pebs_supported(void)
 	return boot_cpu_has(X86_FEATURE_PEBS) && kvm_pmu_cap.pebs_ept;
 }
 
+static inline bool cpu_has_vmx_fred(void)
+{
+	/*
+	 * setup_vmcs_config() guarantees FRED VM-entry/exit controls
+	 * are either all set or none.  So, no need to check FRED VM-exit
+	 * controls.
+	 */
+	return cpu_feature_enabled(X86_FEATURE_FRED) &&
+		(vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_FRED);
+}
+
 static inline bool cpu_has_notify_vmexit(void)
 {
 	return vmcs_config.cpu_based_2nd_exec_ctrl &
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index e38545d0dd17..ab84939ace96 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -8052,6 +8052,9 @@ static __init void vmx_set_cpu_caps(void)
 		kvm_cpu_cap_check_and_set(X86_FEATURE_DTES64);
 	}
 
+	if (!cpu_has_vmx_fred())
+		kvm_cpu_cap_clear(X86_FEATURE_FRED);
+
 	if (!enable_pmu)
 		kvm_cpu_cap_clear(X86_FEATURE_PDCM);
 	kvm_caps.supported_perf_cap = vmx_get_perf_capabilities();
-- 
2.48.1