Qemu 0.14.1 released!

I just found out that a new version of Qemu has hit the street!  From the changelog:

  • Version 0.14.1 (commit)
  • virtio-blk: fail unaligned requests (commit)
  • qed: Fix consistency check on 32-bit hosts (commit)
  • exit if -drive specified is invalid instead of ignoring the “wrong” -drive (commit)
  • vhost: fix dirty page handling (commit)
  • Do not delete BlockDriverState when deleting the drive (commit)
  • vnc: tight: Fix crash after 2GB of output (commit)
  • lan9118: Ignore write to MAC_VLAN1 register (commit)
  • Don’t allow multiwrites against a block device without underlying medium (commit)
  • lsi53c895a: add support for ABORT messages (commit)
  • virtio-pci: fix bus master work around on load (commit)
  • fix applesmc REV key (commit)
  • rbd: don’t link with -lcrypto (commit)
  • net: Add the missing option declaration of “vhostforce” (commit)
  • lsi53c895a: Update dnad when skipping MSGOUT bytes (commit)
  • Revert “prep: Disable second IDE channel, as long as ISA IDE emulation doesn’t support same irq for both channels” (commit)
  • isa-bus: Remove bogus IRQ sharing check (commit)
  • virtio-net: Fix lduw_p() pointer argument of wrong size (commit)
  • hw/sd.c: Add missing state change for SD_STATUS, SEND_NUM_WR_BLOCKS (commit)
  • vnc: Fix fatal crash with vnc reverse mode (commit)
  • qemu-char: Check for missing backend name (commit)

I’ve also included my patches to enable ctrl+alt+d for a quick control alt delete, ctrl+alt+r for reset, and the ISA Cirrus adapter.

As always, I’ll have win32 builds up in the usual spot.  i386/x86_64 and everything else.  I’ve tested these on Windows 7 x86_64, and they should work on XP & Vista i386 as well.

Also I’ve switched this to 7zip to save space.


11 thoughts on “Qemu 0.14.1 released!

  1. It was a lot easier to setup than I had anticipated… Then again the last time I looked at doing this it was 2007… I’m sure things have gotten a lot better since then!

    And thanks!

  2. Qemu operates at low speed with a virtual hard disk. I tried to format raw, qcow, vdi. On Windows XP 32-bit everything is fine. But for Windows 7 64-bit is such a problem. MS-DOS 6.22 is installed in Qemu on Windows 7, a few minutes, but on XP for a few seconds. Tried Qemu 0.14.0, 0.14.1, 0.15.0. Why such a low speed? 🙁 In Safe Mode, Windows 7 is still a problem, too. How to solve this problem on Windows 7? Can you help? Thanks in advance.
    Sorry for my English.

    • I’ve never benchmarked the speed of the disks… I know that expanding/growing a qcow/qcow2/vmdk/vpc image can be quite painful, however if RAW is slow as well… That’d be quite bad.

      How much memory do you have?

        • I have no idea… here is a small test I just ran with Qemu 0.15.0 …

          # time dd if=/dev/zero of=bla bs=1000000 count=50
          50+0 records in
          50+0 records out
          50000000 bytes transferred in 48.727 secs (1026116 bytes/sec)
          0m48.76s real 0m0.00s user 0m9.64s system

  3. Yes! 🙂 Problem solved! The problem was related to the write caching on the hard drive. Caching in Qemu depends on the parameter “-cache cacheparameter” in “-drive”. This option is described in detail in the documentation. cacheparameter is “none”, “writeback”, “unsafe”, or “writethrough”. “directsync” is in the documentation, but I have not worked. With and without caching – different speed of the disc.
    I tested the write speed to virtual hard disk.
    Checked the speed install MS-DOS 6.22 in Qemu 0.14.1 and 0.15.0.
    fast – copying files takes 1 – 2 seconds with a single floppy.
    slow – copying files takes longer than 20 seconds (maybe even more than one minute) with a single floppy.
    Columns – parameters of cache.
    Rows – virtual hard disk formats.
    Host OS – Windows 7 64-bit
    Qemu 0.14.1 =>
    | raw | slow | fast | fast |slow |
    | qcow | slow | slow* | fast | slow|
    | qcow2 | slow | fast | fast | slow|
    | vdi | slow | fast | fast | slow|
    Qemu 0.15.0 =>
    | raw | slow | fast | fast |fast |
    | qcow | slow | slow* | fast | slow|
    | qcow2 | slow | fast | fast | fast|
    | vdi | slow | fast | fast | fast|
    * – Why slow? I don’t know. 🙁
    Interesting test results.
    “writethrough” option is the default. The result was a low speed of write to the virtual hard disk.
    I replaced “-hda disk1.qcow2” to
    “-drive file=disk1.qcow2,if=ide,index=0,media=disk,cache=writeback”
    And it works fast.

    • Wow that is some fantastic information!!! I’ll have to crib that and write it up! but that is amazing I never even though to dig that far!!!!!

    • Previous testing was on Windows 7 64-bit with Service Pack 1.
      I spent testing on Windows XP SP3 32-bit. The results were different from the results on Windows 7.
      Results Qemu 0.14.1 and 0.15.0 turned out the same.
      Columns – parameters of cache.
      Rows – virtual hard disk formats.
      Host OS – Windows XP SP3 32-bit
      Qemu 0.14.1 & 0.15.0 =>
      | raw | fast | fast | fast | fast|
      | qcow | fast | slow | fast | slow|
      | qcow2 | medium* | fast | fast | fast|
      | vdi | fast | fast | fast | fast|
      * – There was a significant slowdown, but still the speed was high enough (about 3 – 5 seconds).
      Since “writethrough” option is the default, it becomes clear why the write speed to a virtual hard drive was high on Windows XP. (maybe it becomes clear)

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