Advertise the support of EPT to the L1 guest, through the appropriate MSR.

This is the last patch of the basic Nested EPT feature, so as to allow
bisection through this patch series: The guest will not see EPT support until
this last patch, and will not attempt to use the half-applied feature.
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Nadav Har'El <nyh@il.ibm.com>
Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>
Signed-off-by: Xinhao Xu <xinhao.xu@intel.com>
Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx.c

@@ -2250,6 +2250,22 @@ static __init void nested_vmx_setup_ctls_msrs(void)
 		SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
 		SECONDARY_EXEC_WBINVD_EXITING;
 
+	if (enable_ept) {
+		/* nested EPT: emulate EPT also to L1 */
+		nested_vmx_secondary_ctls_high |= SECONDARY_EXEC_ENABLE_EPT;
+		nested_vmx_ept_caps = VMX_EPT_PAGE_WALK_4_BIT;
+		nested_vmx_ept_caps |= VMX_EPT_INVEPT_BIT;
+		nested_vmx_ept_caps &= vmx_capability.ept;
+		/*
+		 * Since invept is completely emulated we support both global
+		 * and context invalidation independent of what host cpu
+		 * supports
+		 */
+		nested_vmx_ept_caps |= VMX_EPT_EXTENT_GLOBAL_BIT |
+			VMX_EPT_EXTENT_CONTEXT_BIT;
+	} else
+		nested_vmx_ept_caps = 0;
+
 	/* miscellaneous data */
 	rdmsr(MSR_IA32_VMX_MISC, nested_vmx_misc_low, nested_vmx_misc_high);
 	nested_vmx_misc_low &= VMX_MISC_PREEMPTION_TIMER_RATE_MASK |
@@ -2358,8 +2374,8 @@ static int vmx_get_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
 					nested_vmx_secondary_ctls_high);
 		break;
 	case MSR_IA32_VMX_EPT_VPID_CAP:
-		/* Currently, no nested ept or nested vpid */
-		*pdata = 0;
+		/* Currently, no nested vpid support */
+		*pdata = nested_vmx_ept_caps;
 		break;
 	default:
 		return 0;