Re: [PATCH 00/12] Fix PM hibernation in Xen guests

["Agarwal, Anchal" <anchalag@amazon.com>]

A gentle ping on this whole patch series.

Thanks,
Anchal

    Hello,
    This series fixes PM hibernation for hvm guests running on xen hypervisor.
    The running guest could now be hibernated and resumed successfully at a
    later time. The fixes for PM hibernation are added to block and
    network device drivers i.e xen-blkfront and xen-netfront. Any other driver
    that needs to add S4 support if not already, can follow same method of
    introducing freeze/thaw/restore callbacks.
    The patches had been tested against upstream kernel and xen4.11. Large
    scale testing is also done on Xen based Amazon EC2 instances. All this testing
    involved running memory exhausting workload in the background.

    Doing guest hibernation does not involve any support from hypervisor and
    this way guest has complete control over its state. Infrastructure
    restrictions for saving up guest state can be overcome by guest initiated
    hibernation.

    These patches were send out as RFC before and all the feedback had been
    incorporated in the patches. The last RFCV3 could be found here:
    https://lkml.org/lkml/2020/2/14/2789

    Known issues:
    1.KASLR causes intermittent hibernation failures. VM fails to resumes and
    has to be restarted. I will investigate this issue separately and shouldn't
    be a blocker for this patch series.
    2. During hibernation, I observed sometimes that freezing of tasks fails due
    to busy XFS workqueuei[xfs-cil/xfs-sync]. This is also intermittent may be 1
    out of 200 runs and hibernation is aborted in this case. Re-trying hibernation
    may work. Also, this is a known issue with hibernation and some
    filesystems like XFS has been discussed by the community for years with not an
    effectve resolution at this point.

    Testing How to:
    ---------------
    1. Setup xen hypervisor on a physical machine[ I used Ubuntu 16.04 +upstream
    xen-4.11]
    2. Bring up a HVM guest w/t kernel compiled with hibernation patches
    [I used ubuntu18.04 netboot bionic images and also Amazon Linux on-prem images].
    3. Create a swap file size=RAM size
    4. Update grub parameters and reboot
    5. Trigger pm-hibernation from within the VM

    Example:
    Set up a file-backed swap space. Swap file size>=Total memory on the system
    sudo dd if=/dev/zero of=/swap bs=$(( 1024 * 1024 )) count=4096 # 4096MiB
    sudo chmod 600 /swap
    sudo mkswap /swap
    sudo swapon /swap

    Update resume device/resume offset in grub if using swap file:
    resume=/dev/xvda1 resume_offset=200704 no_console_suspend=1

    Execute:
    --------
    sudo pm-hibernate
    OR
    echo disk > /sys/power/state && echo reboot > /sys/power/disk

    Compute resume offset code:
    "
    #!/usr/bin/env python
    import sys
    import array
    import fcntl

    #swap file
    f = open(sys.argv[1], 'r')
    buf = array.array('L', [0])

    #FIBMAP
    ret = fcntl.ioctl(f.fileno(), 0x01, buf)
    print buf[0]
    "


    Anchal Agarwal (5):
      x86/xen: Introduce new function to map HYPERVISOR_shared_info on
        Resume
      genirq: Shutdown irq chips in suspend/resume during hibernation
      xen: Introduce wrapper for save/restore sched clock offset
      xen: Update sched clock offset to avoid system instability in
        hibernation
      PM / hibernate: update the resume offset on SNAPSHOT_SET_SWAP_AREA

    Munehisa Kamata (7):
      xen/manage: keep track of the on-going suspend mode
      xenbus: add freeze/thaw/restore callbacks support
      x86/xen: add system core suspend and resume callbacks
      xen-blkfront: add callbacks for PM suspend and hibernation
      xen-netfront: add callbacks for PM suspend and hibernation
      xen/time: introduce xen_{save,restore}_steal_clock
      x86/xen: save and restore steal clock

     arch/x86/xen/enlighten_hvm.c      |   8 ++
     arch/x86/xen/suspend.c            |  72 ++++++++++++++++++
     arch/x86/xen/time.c               |  18 ++++-
     arch/x86/xen/xen-ops.h            |   3 +
     drivers/block/xen-blkfront.c      | 122 ++++++++++++++++++++++++++++--
     drivers/net/xen-netfront.c        |  98 +++++++++++++++++++++++-
     drivers/xen/events/events_base.c  |   1 +
     drivers/xen/manage.c              |  73 ++++++++++++++++++
     drivers/xen/time.c                |  29 ++++++-
     drivers/xen/xenbus/xenbus_probe.c |  99 +++++++++++++++++++-----
     include/linux/irq.h               |   2 +
     include/xen/xen-ops.h             |   8 ++
     include/xen/xenbus.h              |   3 +
     kernel/irq/chip.c                 |   2 +-
     kernel/irq/internals.h            |   1 +
     kernel/irq/pm.c                   |  31 +++++---
     kernel/power/user.c               |   6 +-
     17 files changed, 536 insertions(+), 40 deletions(-)

    -- 
    2.24.1.AMZN