Comment 0 for bug 1894895

Description of problem:
On Azure, if the VM is Stopped(deallocated) and later Started, the VF NIC's VMBus Instance GUID may change, and as a result hibernation/resume can hang forever.

This happens to the latest stable release of the linux-azure 5.4.0-1023.23 kernel and the latest mainline linux kernel.

How reproducible:
100%

Steps to Reproduce:
1. Start a VM in Azure that supports Accelerated Networking, and enable hibernation properly (please refer to https://bugs.launchpad.net/ubuntu/+source/linux-azure/+bug/1880032/comments/14 )

2. Do hibernation from serial console
# systemctl hibernate

4. After the VM state changes to "Stopped", click "Stop" button from Azure portal to change the VM state to Stopped(deallocated)

5. Wait for some time (e.g. 10 minutes? 1 hour?), and click the "Start" button to start the VM, and then check the boot-up process from the serial console.

Actual results:
Can not boot up. VM hangs after resume.

Starting Resume from hibernation us…6c7-2c0c-491e-adcf-b625d69faf76...
[ 19.822747] PM: resume from hibernation
[ 19.836693] Freezing user space processes ... (elapsed 0.003 seconds) done.
[ 19.846968] OOM killer disabled.
[ 19.850236] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
[ 20.542934] PM: Using 1 thread(s) for decompression
[ 20.548250] PM: Loading and decompressing image data (559580 pages)...
[ 22.844964] PM: Image loading progress: 0%
[ 28.131327] PM: Image loading progress: 10%
[ 32.346480] PM: Image loading progress: 20%
[ 37.453971] PM: Image loading progress: 30%
[ 40.834525] PM: Image loading progress: 40%
[ 42.980629] PM: Image loading progress: 50%
[ 44.342959] PM: Image loading progress: 60%
[ 45.506197] PM: Image loading progress: 70%
[ 46.800445] PM: Image loading progress: 80%
[ 48.010185] PM: Image loading progress: 90%
[ 49.045671] PM: Image loading done
[ 49.050419] PM: Read 2238320 kbytes in 28.48 seconds (78.59 MB/s)
[ 49.074198] printk: Suspending console(s) (use no_console_suspend to debug)

(The VM hangs here forever)

BUG FIX:
A workaround patch is available and is being reviewed: https://lkml.org/lkml/2020/9/4/1270