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Re: [Qemu-discuss] Hang on reboot in FreeBSD guest on Linux KVM host

From: John Nielsen
Subject: Re: [Qemu-discuss] Hang on reboot in FreeBSD guest on Linux KVM host
Date: Mon, 16 Jun 2014 10:09:25 -0600

[Adding -devel to CC.]

I've opened a bug regarding this issue:


I was unable to duplicate the issue in a different hypervisor, so it seems 
likely the problem (or at least its solution) is in Qemu. Any ideas or feedback 
still very much appreciated.


On May 9, 2014, at 2:12 PM, John Nielsen <address@hidden> wrote:

> I am trying to solve a problem with x86_64 FreeBSD virtual machines running 
> on a Linux+libvirt+KVM hypervisor. To be honest I'm not sure if the problem 
> is in FreeBSD or the hypervisor, but I'm trying to approach it from both 
> directions.
> The _second_ time FreeBSD boots in a virtual machine with more than one core, 
> the boot hangs just before the kernel would normally bring up the additional 
> processors. The VM will boot fine a first time, but running either "shutdown 
> -r now" OR "reboot" will lead to a hung second boot. Stopping and starting 
> the host qemu-kvm process is the only way to continue.
> Interestingly the problem does not manifest itself after a "virsh reset" on 
> the host. I can also avoid it by patching the guest kernel to skip the SMP 
> part of the shutdown routine.
> Clearly something in the normal FreeBSD shutdown code ls leaving the VM in a 
> bad state that hinders the next boot, but I haven't been able to identify 
> what exactly. Can someone on the list suggest ways to debug this further? 
> Unless it's a FreeBSD bug, I'd like to find a solution or workaround that 
> doesn't involve modifying the guest OS.
> One more thing: the problem only appears on one of two clusters of host 
> machines. The hosts within each cluster are identical, and the two clusters 
> are _nearly_ identical to each other. All are running the same software, 
> including:
>  CentOS 6.5
>  kernel 3.12.13 (custom)
>  libvirt-1.1.4-2.el6
>  qemu-kvm-1.7.0-2.el6
>  seabios-
> The only substantial difference on the hardware side is the CPU. The hosts 
> where the problem occurs use "Intel(R) Xeon(R) CPU E5-2650 v2 @ 2.60GHz", 
> while the hosts that don't show the problem use the prior revision, "Intel(R) 
> Xeon(R) CPU E5-2650 0 @ 2.00GHz".
> All ideas appreciated.

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