From: Jim Mattson <jmattson@google.com>
Date: Wed, 23 Aug 2017 16:32:04 -0700
Subject: kvm: vmx: Raise #UD on unsupported RDRAND
Patch-mainline: v4.14-rc1
Git-commit: 45ec368c9addbbf3fb25fc33d3f22f838ec91714
References: bsc#1077761

A guest may not be configured to support RDRAND, even when the host
does. If the guest does not support RDRAND, intercept the instruction
and synthesize #UD. Also clear the "allowed-1" bit for RDRAND exiting
in the IA32_VMX_PROCBASED_CTLS2 MSR.

Signed-off-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Alexander Graf <agraf@suse.de>
---
 arch/x86/kvm/vmx.c |   31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2808,7 +2808,7 @@
 		vmx->nested.nested_vmx_secondary_ctls_high);
 	vmx->nested.nested_vmx_secondary_ctls_low = 0;
 	vmx->nested.nested_vmx_secondary_ctls_high &=
-		SECONDARY_EXEC_RDRAND | SECONDARY_EXEC_RDSEED |
+		SECONDARY_EXEC_RDSEED |
 		SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
 		SECONDARY_EXEC_DESC |
 		SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE |
@@ -3661,6 +3661,7 @@
 			SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY |
 			SECONDARY_EXEC_SHADOW_VMCS |
 			SECONDARY_EXEC_XSAVES |
+			SECONDARY_EXEC_RDRAND |
 			SECONDARY_EXEC_ENABLE_PML |
 			SECONDARY_EXEC_TSC_SCALING |
 			SECONDARY_EXEC_ENABLE_VMFUNC;
@@ -5256,6 +5257,12 @@
 	return exec_control;
 }
 
+static bool vmx_rdrand_supported(void)
+{
+	return vmcs_config.cpu_based_2nd_exec_ctrl &
+		SECONDARY_EXEC_RDRAND;
+}
+
 static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx)
 {
 	struct kvm_vcpu *vcpu = &vmx->vcpu;
@@ -5325,6 +5332,21 @@
 		}
 	}
 
+	if (vmx_rdrand_supported()) {
+		bool rdrand_enabled = guest_cpuid_has(vcpu, X86_FEATURE_RDRAND);
+		if (rdrand_enabled)
+			exec_control &= ~SECONDARY_EXEC_RDRAND;
+
+		if (nested) {
+			if (rdrand_enabled)
+				vmx->nested.nested_vmx_secondary_ctls_high |=
+					SECONDARY_EXEC_RDRAND;
+			else
+				vmx->nested.nested_vmx_secondary_ctls_high &=
+					~SECONDARY_EXEC_RDRAND;
+		}
+	}
+
 	vmx->secondary_exec_control = exec_control;
 }
 
@@ -6830,6 +6852,12 @@
 	return handle_nop(vcpu);
 }
 
+static int handle_invalid_op(struct kvm_vcpu *vcpu)
+{
+	kvm_queue_exception(vcpu, UD_VECTOR);
+	return 1;
+}
+
 static int handle_monitor_trap(struct kvm_vcpu *vcpu)
 {
 	return 1;
@@ -8073,6 +8101,7 @@
 	[EXIT_REASON_MONITOR_INSTRUCTION]     = handle_monitor,
 	[EXIT_REASON_INVEPT]                  = handle_invept,
 	[EXIT_REASON_INVVPID]                 = handle_invvpid,
+	[EXIT_REASON_RDRAND]                  = handle_invalid_op,
 	[EXIT_REASON_XSAVES]                  = handle_xsaves,
 	[EXIT_REASON_XRSTORS]                 = handle_xrstors,
 	[EXIT_REASON_PML_FULL]		      = handle_pml_full,