KVM: VMX: remove special CPL cache access during transition to real mode.

Since vmx_get_cpl() always returns 0 when VCPU is in real mode it is no
longer needed. Also reset CPL cache to zero during transaction to
protected mode since transaction may happen while CS.selectors & 3 != 0,
but in reality CPL is 0.
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/vmx.c

@@ -2817,6 +2817,10 @@ static void enter_pmode(struct kvm_vcpu *vcpu)
 	fix_pmode_dataseg(vcpu, VCPU_SREG_DS, &vmx->rmode.segs[VCPU_SREG_DS]);
 	fix_pmode_dataseg(vcpu, VCPU_SREG_FS, &vmx->rmode.segs[VCPU_SREG_FS]);
 	fix_pmode_dataseg(vcpu, VCPU_SREG_GS, &vmx->rmode.segs[VCPU_SREG_GS]);
+
+	/* CPL is always 0 when CPU enters protected mode */
+	__set_bit(VCPU_EXREG_CPL, (ulong *)&vcpu->arch.regs_avail);
+	vmx->cpl = 0;
 }
 
 static gva_t rmode_tss_base(struct kvm *kvm)
@@ -3229,14 +3233,6 @@ static int vmx_get_cpl(struct kvm_vcpu *vcpu)
 	    && (kvm_get_rflags(vcpu) & X86_EFLAGS_VM)) /* if virtual 8086 */
 		return 3;
 
-	/*
-	 * If we enter real mode with cs.sel & 3 != 0, the normal CPL calculations
-	 * fail; use the cache instead.
-	 */
-	if (unlikely(vmx->emulation_required && emulate_invalid_guest_state)) {
-		return vmx->cpl;
-	}
-
 	if (!test_bit(VCPU_EXREG_CPL, (ulong *)&vcpu->arch.regs_avail)) {
 		__set_bit(VCPU_EXREG_CPL, (ulong *)&vcpu->arch.regs_avail);
 		vmx->cpl = vmx_read_guest_seg_selector(vmx, VCPU_SREG_CS) & 3;