> From: Mohammed Gamal <mgamal@xxxxxxxxxx> > Sent: Friday, February 10, 2023 1:12 AM > > ... > > Upon crash, Linux sends a CHANNELMSG_UNLOAD messge to the host, > > and the host is supposed to quiesce/reset the VMBus devices, so > > normally we should not see a crash in relid2channel(). > > Does this not happen in the case of kdump? Shouldn't a > CHANNELMSG_UNLOAD > message be sent to the host in that case as well? The message is sent to the host in the case of kdump. > > > > [ 21.906679] Hardware name: Microsoft Corporation Virtual > > > > Machine/Virtual Machine, BIOS 090007 05/18/2018 > > > > I guess you see the crash because you're running an old Hyper-V, > > probably Windows Server 2016 or 2019, which may be unable to > > reliably handle the guest's CHANNELMSG_UNLOAD messge. > > We've actually seen this on Windows Server 2016, 2019, and 2022. I didn't expect this to happen to WS 2022. It looks like some of the VMBus devices are not reset by the host upon the message CHANNELMSG_UNLOAD. If you can check all the 'relids' in the first kernel beforehand, and print the 'relid' in relid2channel, we'll be able to tell which device is not reset. Maybe it's a good idea to print the 'relid' in the newly-added warning for debug purposes.
