KVM: nVMX: Assume TLB entries of L1 and L2 are tagged differently if L0 use EPT

Since commit 1313cc2bd8f6 ("kvm: mmu: Add guest_mode to kvm_mmu_page_role"),
guest_mode was added to mmu-role and therefore if L0 use EPT, it will
always run L1 and L2 with different EPTP. i.e. EPTP01!=EPTP02.

Because TLB entries are tagged with EP4TA, KVM can assume
TLB entries populated while running L2 are tagged differently
than TLB entries populated while running L1.

Therefore, update nested_has_guest_tlb_tag() to consider if
L0 use EPT instead of if L1 use EPT.

Reviewed-by: Joao Martins <[e-mail]>
Reviewed-by: Krish Sadhukhan <[e-mail]>
Signed-off-by: Liran Alon <[e-mail]>
Signed-off-by: Paolo Bonzini <[e-mail]>

arch/x86/kvm/vmx/nested.c

···
  * populated by L2 differently than TLB entries populated
  * by L1.
  *
- * If L1 uses EPT, then TLB entries are tagged with different EPTP.
+ * If L0 uses EPT, L1 and L2 run with different EPTP because
+ * guest_mode is part of kvm_mmu_page_role. Thus, TLB entries
+ * are tagged with different EPTP.
  *
  * If L1 uses VPID and we allocated a vpid02, TLB entries are tagged
  * with different VPID (L1 entries are tagged with vmx->vpid
···
 {
 	struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
 
-	return nested_cpu_has_ept(vmcs12) ||
+	return enable_ept ||
 	       (nested_cpu_has_vpid(vmcs12) && to_vmx(vcpu)->nested.vpid02);
 }