KVM: x86: Make kvm_hv_get_assist_page() return 0/-errno

Convert kvm_hv_get_assist_page() to return 'int' and propagate possible
errors from kvm_read_guest_cached().
Suggested-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20221101145426.251680-28-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/hyperv.c

@@ -900,14 +900,14 @@ bool kvm_hv_assist_page_enabled(struct kvm_vcpu *vcpu)
 }
 EXPORT_SYMBOL_GPL(kvm_hv_assist_page_enabled);
 
-bool kvm_hv_get_assist_page(struct kvm_vcpu *vcpu)
+int kvm_hv_get_assist_page(struct kvm_vcpu *vcpu)
 {
 	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
 
 	if (!hv_vcpu || !kvm_hv_assist_page_enabled(vcpu))
-		return false;
+		return -EFAULT;
 
-	return !kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.pv_eoi.data,
+	return kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.pv_eoi.data,
 				     &hv_vcpu->vp_assist_page, sizeof(struct hv_vp_assist_page));
 }
 EXPORT_SYMBOL_GPL(kvm_hv_get_assist_page);

arch/x86/kvm/hyperv.h

@@ -108,7 +108,7 @@ int kvm_hv_activate_synic(struct kvm_vcpu *vcpu, bool dont_zero_synic_pages);
 void kvm_hv_vcpu_uninit(struct kvm_vcpu *vcpu);
 
 bool kvm_hv_assist_page_enabled(struct kvm_vcpu *vcpu);
-bool kvm_hv_get_assist_page(struct kvm_vcpu *vcpu);
+int kvm_hv_get_assist_page(struct kvm_vcpu *vcpu);
 
 static inline struct kvm_vcpu_hv_stimer *to_hv_stimer(struct kvm_vcpu *vcpu,
 						      int timer_index)

arch/x86/kvm/vmx/hyperv.c

@@ -326,7 +326,7 @@ u64 nested_get_evmptr(struct kvm_vcpu *vcpu)
 {
 	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
 
-	if (unlikely(!kvm_hv_get_assist_page(vcpu)))
+	if (unlikely(kvm_hv_get_assist_page(vcpu)))
 		return EVMPTR_INVALID;
 
 	if (unlikely(!hv_vcpu->vp_assist_page.enlighten_vmentry))