From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [RFC 1/4] New virtio bus driver Date: Mon, 09 Jul 2007 09:49:13 +0300 Message-ID: <4691DA69.4060204@qumranet.com> References: <20070706124200.988637662@arndb.de> <200707081729.58461.arnd@arndb.de> <4691076B.5050106@qumranet.com> <200707082229.00810.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200707082229.00810.arnd@arndb.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Arnd Bergmann Cc: virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org Arnd Bergmann wrote: > On Sunday 08 July 2007, Avi Kivity wrote: > > >>> Alternatively, we could have a mechanism separate from the >>> virtqueue concept, like a synchronous get_config_data/set_config_data >>> callback into the host driver. >>> >>> >> You also need to allow the host to notify the guest about configuration >> changes. >> > > That is much harder to do, it would require a separate interrupt if you > want to have a device independent mechanism. Most real buses (like PCI) > don't have this, so I'm not sure it's good to do this at the virtio > layer. You already listed the media change notification, which can > be handled without this by either removing and adding the complete > virtio device, or by using a channel for out-of-band data like scsi. > At the very least, we need an interrupt for device hotplug. That same interrupt can be used to notify the guest about configuration changes within a device ("rescan the virtbus and all who sail in her"). -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.