On Wed, Feb 25, 2015 at 06:03:40AM -0700, Eric Blake wrote:
On 02/24/2015 09:52 PM, Martin Kletzander wrote:The problem of having to prevent the reordering of file descriptors when we are building the QEMU command line with file descriptors already exists today. So maybe I could just remove this flag and the related check knowing that reordering of file descriptors and building the QEMU command line that contains file descriptor (from before the order) would not be allowed today without any of the patches I am trying to add.You surely and safely can. The point behind reordering FDs was that when you're using FD passing as done by systemd, those FDs passed must start from number 3. However, because we are already passing a bunch of file descriptors to QEMU and other commands, we *must not* reorder any file descriptors because it wouldn't work, of course.Or we fix the code to ALWAYS reorder file descriptors, including updating the qemu code to use the reordered numbers instead of assuming unchanged passthrough. I'm still in the middle of an audit in my local code base of what that would entail.
I'd be really afraid of that. Not because I wrote the reorder code but mainly because the added one would just add a lot of renumbering that seems pointless to me. Also the reordering is just a hack to make LISTEN_FDS work and I see no other usable case for it.
-- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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