KVM: x86: check DR6/7 high-bits are clear only on long-mode

When the guest sets DR6 and DR7, KVM asserts the high 32-bits are clear, and
otherwise injects a #GP exception. This exception should only be injected only
if running in long-mode.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index a717c13..b362a1a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5184,7 +5184,7 @@
 			return 1;
 		kvm_register_write(vcpu, reg, val);
 	} else
-		if (kvm_set_dr(vcpu, dr, kvm_register_read(vcpu, reg)))
+		if (kvm_set_dr(vcpu, dr, kvm_register_readl(vcpu, reg)))
 			return 1;
 
 	skip_emulated_instruction(vcpu);