Detect of BHyve VM was powered off or rebooted?

[Craig Rodrigues]

On Sun, Feb 9, 2014 at 1:32 PM, Aryeh Friedman <aryeh.friedman at gmail.com>wrote:

>
>
>
> On Sun, Feb 9, 2014 at 4:11 PM, Craig Rodrigues <rodrigc at freebsd.org>wrote:
>
>> Hi,
>>
>> I posted some rc.d scripts that I am using to boot a BHyve VM
>> and send the output to a serial console using the /dev/nmdm
>> driver:
>>
>>
>> http://lists.freebsd.org/pipermail/freebsd-virtualization/2014-January/002040.html
>>
>> It works quite well.  There is some things I would like to improve,
>> and would like some advice on the best way to do it.
>>
>> (1)  If the VM was destroyed with bhyvectl --destroy --vm ${VM_NAME},
>>       then I do not want to automatically restart the VM in the script.
>>       User should manually:  service bhyvevm start
>>
>> (2)  If the VM was powered down, via shutdown -p, or halt -p,
>>        then in my script I do not want to restart the VM in the script.
>>        User should manually:  service bhyvevm start
>>
>> (3)   If the VM was rebooted via "reboot" or "shutdown -r",
>>        then I *do* want the script to restart the VM.
>>
>> I think if I change my start_vm.sh script to do something like:
>>
>>
>>
>> (
>>  while [ -e /dev/vmm/${VM} ]; do
>>     /usr/sbin/bhyve -c 16 -m 8G -A -H -P -g 0 -s 0:0,hostbridge -s 1:0,lpc
>> -s 2:0,virtio-net,${TAP} -s 3:0,virtio-blk,${IMG} -l com1,${CONS_A} ${VM}"
>>  done
>>
>> )  &
>>
>>
>> then this might cover cases (1) and (3), but what will cover
>> case (2)?
>>
>> Thanks for any advice.
>>
>
> The options you gave (which are really the only ones available) do not
> distinguish between the reason for the termination of the instance of bhyve
> pointing to /dev/vmm/XXX  (it just does a normal termination).
>

Did you play with any of these flags to bhyvectl?

       [--get-vmcs-exit-ctls]
       [--get-vmcs-exit-reason]
       [--get-vmcs-exit-qualification]
       [--get-vmcs-exit-interruption-info]

If I do:
bhyvectl --get-vmcs-exit-reason --vm vm1

I get:
vmcs_exit_reason[0]     0x000000000000001e

If I look at:

http://svnweb.freebsd.org/base/head/sys/amd64/vmm/intel/vmcs.h?view=markup#l310

we have:
#define EXIT_REASON_INOUT 30

Linux has this stuff also:
http://lxr.free-electrons.com/source/arch/x86/include/asm/vmx.h?v=3.1#L250

so I guess these values are defined in some Intel manual.



> In my playing with this for almost a month the only solution seems to be
> put a trigger on instance shutdown via whatever method to leave a "cookie"
> file behind on the host (note I have not nor plan to do this in any of my
> own work).
>

Yes, I can see why this might need to be done.  I might need to do that
myself.  However, if bhyvectl can be used to provide adequate status
information as to why the VM exited, I might be able to avoid this.

It would be nicer though if /usr/sbin/bhyve returned
the EXIT_REASON in its status code.



>
>   An other question is it wise to auto-reboot regardless of reason of the
> hypervisor termination?
>

I think the answer is "it depends".  If someone
does "reboot" or "shutdown -r", I think it is reasonable to restart the
VM.  If someone does "halt -p" or "shutdown -p", I think it is reasonable
to not restart the VM.  For any other error condition, I think it is
reasonable to not restart the VM.

I think that there is no  single answer for all users and all applications.
In my case, I am running BHyve VM's as "headless" which
I access via the /dev/nmdm driver.  If the VM reboots normally, I want it
to restart.

 --
Craig