kvm/x86: Pass return code of kvm_emulate_hypercall

Pass the return code from kvm_emulate_hypercall on to the caller,
in order to allow it to indicate to the userspace that
the hypercall has to be handled there.

Also adjust all the existing code paths to return 1 to make sure the
hypercall isn't passed to the userspace without setting kvm_run
appropriately.

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
CC: Gleb Natapov <gleb@kernel.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Joerg Roedel <joro@8bytes.org>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: qemu-devel@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index cb501d3..9f08037 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5758,8 +5758,7 @@
 
 static int handle_vmcall(struct kvm_vcpu *vcpu)
 {
-	kvm_emulate_hypercall(vcpu);
-	return 1;
+	return kvm_emulate_hypercall(vcpu);
 }
 
 static int handle_invd(struct kvm_vcpu *vcpu)