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Date: Wed, 04 Feb 2009 09:21:03 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [patch 18/18] qemu: PCI device, disk and host network
	hot-add / hot-remove
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	<20090204143843.GA26946@redhat.com>
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To: "Daniel P. Berrange" <berrange@redhat.com>, qemu-devel@nongnu.org
Cc: Marcelo Tosatti <mtosatti@redhat.com>

Daniel P. Berrange wrote:
> On Wed, Feb 04, 2009 at 11:33:21AM -0200, Marcelo Tosatti wrote:
>   
>> Add monitor command to hot-add PCI devices (nic and storage).
>>     
>> Syntax is:
>>     
>> pci_add pcibus nic|storage params
>>     
>> It returns the bus slot and function for the newly added device on success.
>>     
>> It is possible to attach a disk to a device after PCI initialization via
>> the drive_add command. If so, a manual scan of the SCSI bus on the guest
>> is necessary.
>>     
>> Save QEMUMachine necessary for drive_init.
>>     
>> Add monitor command to hot-remove devices, remove device data on _EJ0 notification.
>>     
>
> Does this allow for hot-add of host TAP devices passing a open
> file descriptor across with SCM_RIGHTS (man 7 unix) on the UNIX
> domain socket connection to the monitor ?   This ability is
> critical for libvirt, because we need to be able to allocate the
> TAP devices ourselves & do various configuration tasks before giving
> them to QEMU - the external script capability isn't suitable /flexible
> enough for this.
>   

It doesn't support this today but additional patches to enable that are 
certainly welcome.  The best way would be a generic mechanism to send a 
file descriptor to QEMU that could then be used anywhere fd= is valid.  
For instance:

(qemu) receivefd unix:foo.sock,server
fd=5
(qemu) closefd 5

Regards,

Anthony Liguori

> Regards,
> Daniel
>