KVM: VMX: Don't allow uninhibited access to EFER on i386

vmx_set_msr() does not allow i386 guests to touch EFER, but they can still
do so through the default: label in the switch.  If they set EFER_LME, they
can oops the host.

Fix by having EFER access through the normal channel (which will check for
EFER_LME) even on i386.

Reported-and-tested-by: Benjamin Gilbert <bgilbert@cs.cmu.edu>
Cc: stable@kernel.org
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/vmx.c

@@ -936,11 +936,11 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
 	int ret = 0;
 
 	switch (msr_index) {
-#ifdef CONFIG_X86_64
 	case MSR_EFER:
 		vmx_load_host_state(vmx);
 		ret = kvm_set_msr_common(vcpu, msr_index, data);
 		break;
+#ifdef CONFIG_X86_64
 	case MSR_FS_BASE:
 		vmcs_writel(GUEST_FS_BASE, data);
 		break;