Re: [Qemu-devel] [PATCH v3 0/4] command line fd passing using fd sets

[Corey Bryant <coreyb@linux.vnet.ibm.com>]

On 10/16/2012 03:26 PM, Eric Blake wrote:
> On 10/16/2012 11:51 AM, Corey Bryant wrote:
>> This series adds command line file descriptor passing support
>> via a new -add-fd option.  This is a follow-on to the existing
>> QMP fd passing support provided in the following patch series:
>> comments.gmane.org/gmane.comp.emulators.qemu/165463
>>
>> The new -add-fd option is designed to mirror the add-fd QMP
>> option as much as possible.
>
> Before this can still be useful in libvirt, we need a way to pass in fds
> for all of a backing chain, and not just the top-level.  And you can't
> argue that libvirt should be temporarily rewriting qcow2 metadata to
> stick in names such as /dev/fdset/1 into the metadata.  Consider the
> case of:
>
>                          /- guest1.img
> base.img <- snap1.img <
>                          \- guest2.img
>
> snap1.img is supposed to be read-only, and there's no guarantee that
> /dev/fdset/1 will be available for both guest1 and guest2 to rewrite the
> header.  Thus, I argue that snap1.img must encode the name base.img in
> its metadata, but that we must also have a way to tell qemu to open
> /dev/fdset/1 instead of trying open(base.img) in order to get the open
> fd for base.img.

I think the -blockdev command is going to solve this.

Stefan, do you have any information on the -blockdev support?

>
> But even though we are still not at a point where the overall feature is
> useful, I can at least review these patches for getting us incrementally
> closer to our goal.
>

Thanks Eric.


-- 
Regards,
Corey Bryant