KVM: x86/mmu: Sync roots after MMU load iff load as successful

For clarity, explicitly skip syncing roots if the MMU load failed
instead of relying on the !VALID_PAGE check in kvm_mmu_sync_roots().

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-17-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -4836,10 +4836,11 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu)
 	else
 		r = mmu_alloc_shadow_roots(vcpu);
 	write_unlock(&vcpu->kvm->mmu_lock);
-
-	kvm_mmu_sync_roots(vcpu);
 	if (r)
 		goto out;
+
+	kvm_mmu_sync_roots(vcpu);
+
 	kvm_mmu_load_pgd(vcpu);
 	static_call(kvm_x86_tlb_flush_current)(vcpu);
 out: