Bug 624189

*** This bug has been marked as a duplicate of bug 609286 ***

Each virtio driver needs to be updated to handle PM, so re-opening this.

This request was evaluated by Red Hat Product Management for inclusion
in a Red Hat Enterprise Linux maintenance release. Product Management has 
requested further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed 
products. This request is not yet committed for inclusion in an Update release.

Patch(es) available on kernel-2.6.32-231.el6

Note that after resuming from S4, the virtio balloon driver will completely deflate the balloon.  This is as designed, and is explained in the commit log:

Linux kernel commit e562966dbaf49e7804097cd991e5d3a8934fc148

    virtio: balloon: Add freeze, restore handlers to support S4
    
    Handling balloon hibernate / restore is tricky.  If the balloon was
    inflated before going into the hibernation state, upon resume, the host
    will not have any memory of that.  Any pages that were passed on to the
    host earlier would most likely be invalid, and the host will have to
    re-balloon to the previous value to get in the pre-hibernate state.
    
    So the only sane thing for the guest to do here is to discard all the
    pages that were put in the balloon.  When to discard the pages is the
    next question.
    
    One solution is to deflate the balloon just before writing the image to
    the disk (in the freeze() PM callback).  However, asking for pages from
    the host just to discard them immediately after seems wasteful of
    resources.  Hence, it makes sense to do this by just fudging our
    counters soon after wakeup.  This means we don't deflate the balloon
    before sleep, and also don't put unnecessary pressure on the host.
    
    This also helps in the thaw case: if the freeze fails for whatever
    reason, the balloon should continue to remain in the inflated state.
    This was tested by issuing 'swapoff -a' and trying to go into the S4
    state.  That fails, and the balloon stays inflated, as expected.  Both
    the host and the guest are happy.
    
    Finally, in the restore() callback, we empty the list of pages that were
    previously given off to the host, add the appropriate number of pages to
    the totalram_pages counter, reset the num_pages counter to 0, and
    all is fine.
    
    As a last step, delete the vqs on the freeze callback to prepare for
    hibernation, and re-create them in the restore and thaw callbacks to
    resume normal operation.
    
    The kthread doesn't race with any operations here, since it's frozen
    before the freeze() call and is thawed after the thaw() and restore()
    callbacks, so we're safe with that.

(In reply to comment #8)
> Note that after resuming from S4, the virtio balloon driver will completely
> deflate the balloon.  This is as designed, and is explained in the commit log:

Ignore this; Bug 798583 tracks a fix to the optimisation that prevented the re-ballooning after restore.

Once the fix for that bug lands in, the previous value of the balloon will be applied after restore.

Verified this bug on kernel-2.6.32-262.el6.x86_64, this issue does not exist.

CLI:

/usr/libexec/qemu-kvm -M rhel6.3.0 -cpu Conroe -enable-kvm -m 2G -smp 2,sockets=1,cores=2,threads=1 -name rhel6.3 -uuid 4c84db67-faf8-4498-9829-19a3d6431d9d -rtc base=localtime,driftfix=slew -netdev tap,id=hostnet0,vhost=on,script=/etc/qemu-ifup -device virtio-net-pci,netdev=hostnet0,id=net0,mac=00:1a:2a:42:10:62,bus=pci.0,addr=0x3 -boot c -monitor stdio -spice port=5930,disable-ticketing -vga qxl -global qxl-vga.vram_size=33554432 -qmp tcp:0:4444,server,nowait -bios /usr/share/seabios/bios-pm.bin  -chardev socket,path=/tmp/qzhang-test-lucky,server,nowait,id=isa1 -device isa-serial,chardev=isa1,id=isa-serial1 -drive file=/dev/vgtest-qzhang/lv-6.3,if=none,format=qcow2,id=scsi0 -device virtio-scsi-pci,id=scsi0 -device scsi-disk,bus=scsi0.0,drive=scsi0,scsi-id=0,lun=0 -drive if=none,id=cd -device scsi-cd,drive=cd -usb -device usb-tablet,id=input0 -device virtio-balloon-pci,id=balloon0,bus=pci.0

(1) S3 -> wakeup -> balloon memory to other value. => Pass.
(2) Balloon mem to less value -> S3 -> wakeup -> balloon mem. => Pass
(3) S4 -> resume -> balloon memory => Pass
(4) Balloon memory -> S4 -> resume -> balloon mem. => Pass
(5) Do S3 and S4 alternately -> balloon mem => Pass

Based above, this issue is fixed.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2012-0862.html