[PATCH 4.18 06/44] KVM: VMX: check for existence of secondary exec controls before accessing

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sean Christopherson <sean.j.christopherson@intel.com>

commit fd6b6d9b82f97a851fb0078201ddc38fe9728cda upstream.

Return early from vmx_set_virtual_apic_mode() if the processor doesn't
support VIRTUALIZE_APIC_ACCESSES or VIRTUALIZE_X2APIC_MODE, both of
which reside in SECONDARY_VM_EXEC_CONTROL.  This eliminates warnings
due to VMWRITEs to SECONDARY_VM_EXEC_CONTROL (VMCS field 401e) failing
on processors without secondary exec controls.

Remove the similar check for TPR shadowing as it is incorporated in the
flexpriority_enabled check and the APIC-related code in
vmx_update_msr_bitmap() is further gated by VIRTUALIZE_X2APIC_MODE.

Reported-by: Gerhard Wiesinger <redhat@wiesinger.com>
Fixes: 8d860bbeedef ("kvm: vmx: Basic APIC virtualization controls have three settings")
Cc: Jim Mattson <jmattson@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kvm/vmx.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -9826,15 +9826,16 @@ static void vmx_set_virtual_apic_mode(st
 	if (!lapic_in_kernel(vcpu))
 		return;
 
+	if (!flexpriority_enabled &&
+	    !cpu_has_vmx_virtualize_x2apic_mode())
+		return;
+
 	/* Postpone execution until vmcs01 is the current VMCS. */
 	if (is_guest_mode(vcpu)) {
 		to_vmx(vcpu)->nested.change_vmcs01_virtual_apic_mode = true;
 		return;
 	}
 
-	if (!cpu_need_tpr_shadow(vcpu))
-		return;
-
 	sec_exec_control = vmcs_read32(SECONDARY_VM_EXEC_CONTROL);
 	sec_exec_control &= ~(SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
 			      SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE);