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

[Eric Blake <eblake@redhat.com>]

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On 10/05/2012 12:07 PM, Corey Bryant wrote:
> This series adds command line file descriptor passing support
> to the -drive 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
> 
> An example of using the new -drive fd and opaque options:
> qemu-kvm -drive fd=24,opaque="rdwr:/path/file",index=0,media=disk

This feels wrong.  Now you have to special-case encode the
fd=nn,opaque=xyz handling to EVERY command line argument that takes a
file name, not just -drive.

I'd much rather see:

qemu-kvm -fdset set=1,fds=24,25 \
  -drive file=/def/fdset/1,index=0,media=disk

Where the creation of fdsets happens independently from use of those
sets, and therefore all other arguments that take file names can just
magically take the /dev/fdset/nnn notation that we already support from
the monitor.

Besides, my approach will let me pass in an O_RDONLY fd on 24 and O_RDWR
on 25 into the same set, whereas your approach creates a new set per fd,
so I can't add new fds to the set until the monitor is up and running.

-- 
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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