[libvirt] [RFC PATCHv2 0/3] outgoing migration via fd: rather than exec:

Posted as an RFC because there are still two open bugs to be solved. I've tested that with this installed, I was able to do 'virsh save domain file' without compression to a local file using qemu fd: migration. 1. I'm working on making virFileOperation use SCM_RIGHTS so that we can pass an arbitrary fd from the child back to the parent. This is necessary for supporting root-squash NFS domain save via fd, since a child cannot consistently modify the appropriate locks necessary to issue a monitor command (the current virFileOperation implementation guarantees that the hook will execute on the right fd, but does not guarantee whether the operation is in the parent or a child, and thus the operation is not permitted to modify any state in the parent other than by its return value). The current state of the patch just falls back to exec: migration if the parent process can't reopen the fd. 2. I also need to test for qemu capabilities, as qemu 0.11.0 does _not_ support fd: migration, so the old exec: migration path must remain. But checking for capabilities is a bear in itself, since we should be caching qemu capabilities when a domain is started, and not calling 'qemu -help' for every subsequent command that needs to know. Eric Blake (3): qemu: use lighter-weight fd:n on incoming tunneled migration qemu: support migration to fd qemu: allow simple domain save to use fd: protocol src/qemu/qemu_driver.c | 16 ++++++++++++-- src/qemu/qemu_migration.c | 44 +++++++++++------------------------------ src/qemu/qemu_monitor.c | 22 +++++++++++++++++++++ src/qemu/qemu_monitor.h | 4 +++ src/qemu/qemu_monitor_json.c | 21 +++++++++++++++++++- src/qemu/qemu_monitor_json.h | 6 ++++- src/qemu/qemu_monitor_text.c | 24 +++++++++++++++++++++- src/qemu/qemu_monitor_text.h | 6 ++++- 8 files changed, 103 insertions(+), 40 deletions(-) -- 1.7.4