Re: // a kdump hang caused by PPC pci patch series

Sorry that forget a subject.

On Mon, Nov 21, 2022 at 7:54 PM Pingfan Liu [off-list ref] wrote:

Hello Powerpc folks,

I encounter an kdump bug, which I bisect and pin commit 174db9e7f775
("powerpc/pseries/pci: Add support of MSI domains to PHB hotplug")

In that case, using Fedora 36 as host, the mentioned commit as the
guest kernel, and virto-block disk, the kdump kernel will hang:

[    0.000000] Kernel command line: elfcorehdr=0x22c00000
no_timer_check net.ifnames=0 console=tty0 console=hvc0,115200n8
irqpoll maxcpus=1 noirqdistrib reset_devices cgroup_disable=memory
     numa=off udev.children-max=2 ehea.use_mcs=0 panic=10
kvm_cma_resv_ratio=0 transparent_hugepage=never novmcoredd
hugetlb_cma=0
    ...
    [    7.763260] virtio_blk virtio2: 32/0/0 default/read/poll queues
    [    7.771391] virtio_blk virtio2: [vda] 20971520 512-byte logical
blocks (10.7 GB/10.0 GiB)
    [   68.398234] systemd-udevd[187]: virtio2: Worker [190]
processing SEQNUM=1193 is taking a long time
    [  188.398258] systemd-udevd[187]: virtio2: Worker [190]
processing SEQNUM=1193 killed


During my test, I found that in very rare cases, the kdump can success
(I guess it may be due to the cpu id).  And if using either maxcpus=2
or using scsi-disk, then kdump can also success.  And before the
mentioned commit, kdump can also success.

The attachment contains the xml to reproduce that bug.

Do you have any ideas?

Thanks