Panic starting a bhyve guest after resume

[Roger Pau Monné]

On 14/12/13 03:28, Neel Natu wrote:
> Hi John,
> 
> On Fri, Dec 13, 2013 at 2:09 PM, John Baldwin <jhb at freebsd.org> wrote:
>> On Thursday, December 12, 2013 4:00:08 pm Neel Natu wrote:
>>> Hi John,
>>>
>>> On Thu, Dec 12, 2013 at 12:11 PM, John Baldwin <jhb at freebsd.org> wrote:
>>>> If I suspend and resume my laptop and then try to start a guest after the
>>>> resume, I get an odd panic.  It generates a privileged instruction fault (in
>>>> kernel mode) for 'vmclear'.  I've checked CR4 and it claims that VMXE is set.
>>>> I dont have any other ideas off the top of my head on what I should be poking
>>>> at?  It looks like we read a bunch of MSRs in vmx_init(), but we don't write
>>>> to them, and all vmx_enable() does on each CPU is set VMXE in CR4 from what I
>>>> can tell.
>>>>
>>>
>>> It also does a "vmxon" on each logical cpu which may also need to be
>>> done after a resume.
>>
>> Ah, yes it does.  That was sufficient both for starting a new guest after
>> resume and even doing a suspend/resume while a guest was active (and the
>> guest continued to run fine).  I have a hacky patch for this.  One, it
>> includes both a suspend and resume hook for VMM, though for my testing I only
>> needed a resume hook to invoke vmxon.  Second, the name of vmx_resume2()
>> is a total hack (because vmx_resume() was already taken.  I think for now
>> if I were to commit this, I'd just add the resme hook and maybe call the
>> Intel method vmx_reset() or vmx_restore()?
>>
>> http://people.freebsd.org/~jhb/patches/bhyve_resume.patch
>>
> 
> There seems to be a race after the APs are restarted and before
> 'vmm_resume_p()' where it would be problematic to execute a VMX
> instruction.
> 
> Perhaps we should enable VMX on each cpu before they return to the
> interrupted code?

Can you use the hook in cpususpend_handler? It's cpu_ops.cpu_resume, and
gets called on each CPU before returning from the handler.