On Jun 13, 2014, at 4:23 PM, John Nielsen <li...@jnielsen.net> wrote:

> On Wednesday, May 07, 2014 7:15:43 pm John Nielsen wrote:
>> I am trying to solve a problem with amd64 FreeBSD virtual machines running 
>> on a Linux+KVM hypervisor. To be honest I'm not sure if the problem is in 
>> FreeBSD or the hypervisor, but I'm trying to rule out the OS first.
>> 
>> The _second_ time FreeBSD boots in a virtual machine with more than one 
>> core, the boot hangs just before the kernel would normally print e.g. "SMP: 
>> AP CPU #1 Launched!" (The last line on the console is "usbus0: 12Mbps Full 
>> Speed USB v1.0", but the problem persists even without USB). 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.

...

> Following up on the off chance anyone else is interested. I installed -HEAD 
> on a host that was having the problem ("v2" Xeon CPU) and ran a FreeBSD 9 VM 
> under bhyve. The problem did _not_ persist. That's not entirely conclusive 
> but it does point the finger at Qemu a bit more strongly. I have filed a bug 
> with them:
>  https://bugs.launchpad.net/qemu/+bug/1329956

With some help from the Qemu and KVM folks I've finally made some headway. The 
salient difference between the working and non-working CPUs above seems to be 
support for APIC virtualization. Loading the intel_kvm module (on the Linux 
host) with "enable_apicv=N" works around the reboot problem I've been having.

Since this now looks like a Linux KVM bug I won't follow up here any more, but 
I wanted to wrap up the thread for the archives.

JN

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