Re: kexec/kdump of a kvm guest?

Mike Snitzer
2008-07-24T00:13:10Z

On Sat, Jul 5, 2008 at 7:20 AM, Avi Kivity <avi@qumranet.com> wrote:
> Mike Snitzer wrote:
>>
>> My host is x86_64 RHEL5U1 running 2.6.25.4 with kvm-70 (kvm-intel).
>>
>> When I configure kdump in the guest (running 2.6.22.19) and force a
>> crash (with 'echo c > /proc/sysrq-trigger) kexec boots the kdump
>> kernel but then the kernel hangs (before it gets to /sbin/init et al).
>> On the host, the associated qemu is consuming 100% cpu.
>>
>> I really need to be able to collect vmcores from my kvm guests. So
>> far I can't (on raw hardware all works fine).
>>
>>
>
> I've tested this a while ago and it worked (though I tested regular kexecs,
> not crashes); this may be a regression.
>
> Please run kvm_stat to see what's happening at the time of the crash.

OK, I can look into kvm_stat but I just discovered that just having
kvm-intel and kvm loaded into my 2.6.22.19 kernel actually prevents
the host from being able to kexec/kdump too!? I didn't have any
guests running (only the kvm modules were loaded). As soon as I
unloaded the kvm modules kdump worked as expected.

Something about kvm is completely breaking kexec/kdump on both the
host and guest kernels.

Mike