ChangeLog/2.4

System emulation

Command-line compatibility

• Behavior when the three SMP topology options (socket, cores, threads) are specified but don't match the number of VCPUs was changed. In previous versions QEMU silently adjusted the "threads" option to (try to) make the topology match the number of VCPUs, now QEMU will abort when sockets*cores*threads don't match the number of VCPUs.

Future incompatible changes

• Three options are using different names on the command line and in configuration file. In particular:
  • The "acpi" configuration file section matches command-line option "acpitable";
  • The "boot-opts" configuration file section matches command-line option "boot";
  • The "smp-opts" configuration file section matches command-line option "smp".

-readconfig will standardize on the name for the command line option.

• Behavior of automatic calculation of SMP topology when some SMP topology options for -smp are omitted (sockets, cores, threads) will change in the future. If guest ABI needs to be preserved on upgrades while using the SMP topology options, users should either set set all options explicitly (sockets, cores, threads), or omit all of them.
• Image encryption is fatally flawed, and will be dropped entirely. It'll remain available only in qemu-img, so you can use 'qemu-img convert' to convert encrypted images to uncrypted ones.
• Host floppy device pass-through (block driver "host_floppy") is deprecated, and will be dropped in a future release.
• Block device parameter aio=native has no effect without cache.direct=on. It will be made an error.
• A few devices will be configured with explicit properties instead of implicitly. Unlikely to affect users; for the full list, see the 2.3 ChangeLog.
• QMP command blockdev-add is still a work in progress. It doesn't support all block drivers, it lacks a matching blockdev-del, and more. It might change incompatibly.

Build dependencies

• QEMU now requires a minimum glib version of 2.22. (In particular, we will no longer build on a stock RHEL5 or Centos 5 system.)