KVM: nVMX: Don't flush TLB on nested VMX transition

Unconditionally skip the TLB flush triggered when reusing a root for a
nested transition as nested_vmx_transition_tlb_flush() ensures the TLB
is flushed when needed, regardless of whether the MMU can reuse a cached
root (or the last root).
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200320212833.3507-35-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -5034,7 +5034,7 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
 		kvm_calc_shadow_ept_root_page_role(vcpu, accessed_dirty,
 						   execonly, level);
 
-	__kvm_mmu_new_cr3(vcpu, new_eptp, new_role.base, false, true);
+	__kvm_mmu_new_cr3(vcpu, new_eptp, new_role.base, true, true);
 
 	if (new_role.as_u64 == context->mmu_role.as_u64)
 		return;

arch/x86/kvm/vmx/nested.c

@@ -1143,10 +1143,12 @@ static int nested_vmx_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool ne
 	}
 
 	/*
-	 * See nested_vmx_transition_mmu_sync for details on skipping the MMU sync.
+	 * Unconditionally skip the TLB flush on fast CR3 switch, all TLB
+	 * flushes are handled by nested_vmx_transition_tlb_flush().  See
+	 * nested_vmx_transition_mmu_sync for details on skipping the MMU sync.
 	 */
 	if (!nested_ept)
-		kvm_mmu_new_cr3(vcpu, cr3, false,
+		kvm_mmu_new_cr3(vcpu, cr3, true,
 				!nested_vmx_transition_mmu_sync(vcpu));
 
 	vcpu->arch.cr3 = cr3;