Re: [PATCH net-next 12/14] vsock/vmci: register vmci_transport only when VMCI guest/host are active

[Stefano Garzarella]

Hi Jorgen,
I'm preparing the v2, but first, if you have time, I'd like to have
a comment from you on this patch that modifies a bit vmci.

Thank you very much,
Stefano

On Wed, Oct 23, 2019 at 11:55:52AM +0200, Stefano Garzarella wrote:
> 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().
> 
> Cc: Jorgen Hansen <jhansen@xxxxxxxxxx>
> Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> ---
>  drivers/misc/vmw_vmci/vmci_driver.c | 50 +++++++++++++++++++++++++++++
>  drivers/misc/vmw_vmci/vmci_driver.h |  2 ++
>  drivers/misc/vmw_vmci/vmci_guest.c  |  2 ++
>  drivers/misc/vmw_vmci/vmci_host.c   |  7 ++++
>  include/linux/vmw_vmci_api.h        |  2 ++
>  net/vmw_vsock/vmci_transport.c      | 29 +++++++++++------
>  6 files changed, 82 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/misc/vmw_vmci/vmci_driver.c b/drivers/misc/vmw_vmci/vmci_driver.c
> index 819e35995d32..195afbd7edc1 100644
> --- a/drivers/misc/vmw_vmci/vmci_driver.c
> +++ b/drivers/misc/vmw_vmci/vmci_driver.c
> @@ -28,6 +28,9 @@ MODULE_PARM_DESC(disable_guest,
>  static bool vmci_guest_personality_initialized;
>  static bool vmci_host_personality_initialized;
>  
> +static DEFINE_MUTEX(vmci_vsock_mutex); /* protects vmci_vsock_transport_cb */
> +static vmci_vsock_cb vmci_vsock_transport_cb;
> +
>  /*
>   * vmci_get_context_id() - Gets the current context ID.
>   *
> @@ -45,6 +48,53 @@ u32 vmci_get_context_id(void)
>  }
>  EXPORT_SYMBOL_GPL(vmci_get_context_id);
>  
> +/*
> + * vmci_register_vsock_callback() - Register the VSOCK vmci_transport callback.
> + *
> + * The callback will be called every time a new host or guest become active,
> + * or if they are already active when this function is called.
> + * To unregister the callback, call this function with NULL parameter.
> + *
> + * Returns 0 on success. -EBUSY if a callback is already registered.
> + */
> +int vmci_register_vsock_callback(vmci_vsock_cb callback)
> +{
> +	int err = 0;
> +
> +	mutex_lock(&vmci_vsock_mutex);
> +
> +	if (vmci_vsock_transport_cb && callback) {
> +		err = -EBUSY;
> +		goto out;
> +	}
> +
> +	vmci_vsock_transport_cb = callback;
> +
> +	if (!vmci_vsock_transport_cb)
> +		goto out;
> +
> +	if (vmci_guest_code_active())
> +		vmci_vsock_transport_cb(false);
> +
> +	if (vmci_host_users() > 0)
> +		vmci_vsock_transport_cb(true);
> +
> +out:
> +	mutex_unlock(&vmci_vsock_mutex);
> +	return err;
> +}
> +EXPORT_SYMBOL_GPL(vmci_register_vsock_callback);
> +
> +void vmci_call_vsock_callback(bool is_host)
> +{
> +	mutex_lock(&vmci_vsock_mutex);
> +
> +	if (vmci_vsock_transport_cb)
> +		vmci_vsock_transport_cb(is_host);
> +
> +	mutex_unlock(&vmci_vsock_mutex);
> +}
> +
>  static int __init vmci_drv_init(void)
>  {
>  	int vmci_err;
> diff --git a/drivers/misc/vmw_vmci/vmci_driver.h b/drivers/misc/vmw_vmci/vmci_driver.h
> index aab81b67670c..990682480bf6 100644
> --- a/drivers/misc/vmw_vmci/vmci_driver.h
> +++ b/drivers/misc/vmw_vmci/vmci_driver.h
> @@ -36,10 +36,12 @@ extern struct pci_dev *vmci_pdev;
>  
>  u32 vmci_get_context_id(void);
>  int vmci_send_datagram(struct vmci_datagram *dg);
> +void vmci_call_vsock_callback(bool is_host);
>  
>  int vmci_host_init(void);
>  void vmci_host_exit(void);
>  bool vmci_host_code_active(void);
> +int vmci_host_users(void);
>  
>  int vmci_guest_init(void);
>  void vmci_guest_exit(void);
> diff --git a/drivers/misc/vmw_vmci/vmci_guest.c b/drivers/misc/vmw_vmci/vmci_guest.c
> index 7a84a48c75da..cc8eeb361fcd 100644
> --- a/drivers/misc/vmw_vmci/vmci_guest.c
> +++ b/drivers/misc/vmw_vmci/vmci_guest.c
> @@ -637,6 +637,8 @@ static int vmci_guest_probe_device(struct pci_dev *pdev,
>  		  vmci_dev->iobase + VMCI_CONTROL_ADDR);
>  
>  	pci_set_drvdata(pdev, vmci_dev);
> +
> +	vmci_call_vsock_callback(false);
>  	return 0;
>  
>  err_free_irq:
> diff --git a/drivers/misc/vmw_vmci/vmci_host.c b/drivers/misc/vmw_vmci/vmci_host.c
> index 833e2bd248a5..ff3c396146ff 100644
> --- 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);
> +
>  	retval = 0;
>  
>  out:
> diff --git a/include/linux/vmw_vmci_api.h b/include/linux/vmw_vmci_api.h
> index acd9fafe4fc6..f28907345c80 100644
> --- a/include/linux/vmw_vmci_api.h
> +++ b/include/linux/vmw_vmci_api.h
> @@ -19,6 +19,7 @@
>  struct msghdr;
>  typedef void (vmci_device_shutdown_fn) (void *device_registration,
>  					void *user_data);
> +typedef void (*vmci_vsock_cb) (bool is_host);
>  
>  int vmci_datagram_create_handle(u32 resource_id, u32 flags,
>  				vmci_datagram_recv_cb recv_cb,
> @@ -37,6 +38,7 @@ int vmci_doorbell_destroy(struct vmci_handle handle);
>  int vmci_doorbell_notify(struct vmci_handle handle, u32 priv_flags);
>  u32 vmci_get_context_id(void);
>  bool vmci_is_context_owner(u32 context_id, kuid_t uid);
> +int vmci_register_vsock_callback(vmci_vsock_cb callback);
>  
>  int vmci_event_subscribe(u32 event,
>  			 vmci_event_cb callback, void *callback_data,
> diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c
> index 2eb3f16d53e7..04437f822d82 100644
> --- a/net/vmw_vsock/vmci_transport.c
> +++ b/net/vmw_vsock/vmci_transport.c
> @@ -2053,19 +2053,22 @@ static bool vmci_check_transport(struct vsock_sock *vsk)
>  	return vsk->transport == &vmci_transport;
>  }
>  
> -static int __init vmci_transport_init(void)
> +void vmci_vsock_transport_cb(bool is_host)
>  {
> -	int features = VSOCK_TRANSPORT_F_DGRAM | VSOCK_TRANSPORT_F_H2G;
> -	int cid;
> -	int err;
> +	int features;
>  
> -	cid = vmci_get_context_id();
> +	if (is_host)
> +		features = VSOCK_TRANSPORT_F_H2G;
> +	else
> +		features = VSOCK_TRANSPORT_F_G2H;
>  
> -	if (cid == VMCI_INVALID_ID)
> -		return -EINVAL;
> +	vsock_core_register(&vmci_transport, features);
> +}
>  
> -	if (cid != VMCI_HOST_CONTEXT_ID)
> -		features |= VSOCK_TRANSPORT_F_G2H;
> +static int __init vmci_transport_init(void)
> +{
> +	int features = VSOCK_TRANSPORT_F_DGRAM;
> +	int err;
>  
>  	/* Create the datagram handle that we will use to send and receive all
>  	 * VSocket control messages for this context.
> @@ -2079,7 +2082,6 @@ static int __init vmci_transport_init(void)
>  		pr_err("Unable to create datagram handle. (%d)\n", err);
>  		return vmci_transport_error_to_vsock_error(err);
>  	}
> -
>  	err = vmci_event_subscribe(VMCI_EVENT_QP_RESUMED,
>  				   vmci_transport_qp_resumed_cb,
>  				   NULL, &vmci_transport_qp_resumed_sub_id);
> @@ -2094,8 +2096,14 @@ static int __init vmci_transport_init(void)
>  	if (err < 0)
>  		goto err_unsubscribe;
>  
> +	err = vmci_register_vsock_callback(vmci_vsock_transport_cb);
> +	if (err < 0)
> +		goto err_unregister;
> +
>  	return 0;
>  
> +err_unregister:
> +	vsock_core_unregister(&vmci_transport);
>  err_unsubscribe:
>  	vmci_event_unsubscribe(vmci_transport_qp_resumed_sub_id);
>  err_destroy_stream_handle:
> @@ -2121,6 +2129,7 @@ static void __exit vmci_transport_exit(void)
>  		vmci_transport_qp_resumed_sub_id = VMCI_INVALID_ID;
>  	}
>  
> +	vmci_register_vsock_callback(NULL);
>  	vsock_core_unregister(&vmci_transport);
>  }
>  module_exit(vmci_transport_exit);
> -- 
> 2.21.0
> 

--