On Tue, Nov 12, 2019 at 10:03:54AM +0000, Jorgen Hansen wrote: > > From: Stefano Garzarella [mailto:sgarzare@xxxxxxxxxx] > > Sent: Monday, November 11, 2019 6:31 PM > > On Mon, Nov 11, 2019 at 04:27:28PM +0000, Jorgen Hansen wrote: > > > > From: Stefano Garzarella [mailto:sgarzare@xxxxxxxxxx] > > > > Sent: Wednesday, October 23, 2019 11:56 AM > > > > > > > > To allow other transports to be loaded with vmci_transport, > > > > we register the vmci_transport as G2H or H2G only when a VMCI guest > > > > or host is active. > > > > > > > > To do that, this patch adds a callback registered in the vmci driver > > > > that will be called when a new host or guest become active. > > > > This callback will register the vmci_transport in the VSOCK core. > > > > If the transport is already registered, we ignore the error coming > > > > from vsock_core_register(). > > > > > > So today this is mainly an issue for the VMCI vsock transport, because > > > VMCI autoloads with vsock (and with this solution it can continue to > > > do that, so none of our old products break due to changed behavior, > > > which is great). > > > > I tried to not break anything :-) > > > > > Shouldn't vhost behave similar, so that any module > > > that registers a h2g transport only does so if it is in active use? > > > > > > > The vhost-vsock module will load when the first hypervisor open > > /dev/vhost-vsock, so in theory, when there's at least one active user. > > Ok, sounds good then. > > > > > > > > > > --- a/drivers/misc/vmw_vmci/vmci_host.c > > > > +++ b/drivers/misc/vmw_vmci/vmci_host.c > > > > @@ -108,6 +108,11 @@ bool vmci_host_code_active(void) > > > > atomic_read(&vmci_host_active_users) > 0); > > > > } > > > > > > > > +int vmci_host_users(void) > > > > +{ > > > > + return atomic_read(&vmci_host_active_users); > > > > +} > > > > + > > > > /* > > > > * Called on open of /dev/vmci. > > > > */ > > > > @@ -338,6 +343,8 @@ static int vmci_host_do_init_context(struct > > > > vmci_host_dev *vmci_host_dev, > > > > vmci_host_dev->ct_type = VMCIOBJ_CONTEXT; > > > > atomic_inc(&vmci_host_active_users); > > > > > > > > + vmci_call_vsock_callback(true); > > > > + > > > > > > Since we don't unregister the transport if user count drops back to 0, we > > could > > > just call this the first time, a VM is powered on after the module is loaded. > > > > Yes, make sense. can I use the 'vmci_host_active_users' or is better to > > add a new 'vmci_host_vsock_loaded'? > > > > My doubt is that vmci_host_active_users can return to 0, so when it returns > > to 1, we call vmci_call_vsock_callback() again. > > vmci_host_active_users can drop to 0 and then increase again, so having a flag > indicating whether the callback has been invoked would ensure that it is only > called once. I agree, I will use a dedicated flag, maybe in the vmci_call_vsock_callback(), since it can be called or during the vmci_host_do_init_context() or when the callback is registered. Thanks, Stefano
