Re: kernel panic caused by virtualbox(?)

On  8 Aug, Konstantin Belousov wrote:
> On Mon, Aug 08, 2016 at 10:22:44AM -0700, John Baldwin wrote:
>> On Thursday, August 04, 2016 05:10:29 PM Don Lewis wrote:
>> > Reposted to -current to get some more eyes on this ...
>> > 
>> > I just got a kernel panic when I started up a CentOS 7 VM in virtualbox.
>> > The host is:
>> > 	FreeBSD 12.0-CURRENT #17 r302500 GENERIC amd64
>> > The virtualbox version is:
>> > 	virtualbox-ose-5.0.26
>> > 	virtualbox-ose-kmod-5.0.26_1
>> > 
>> > The panic message is:
>> > 
>> > panic: Unregistered use of FPU in kernel
>> > cpuid = 1
>> > KDB: stack backtrace:
>> > db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe085a55d030
>> > vpanic() at vpanic+0x182/frame 0xfffffe085a55d0b0
>> > kassert_panic() at kassert_panic+0x126/frame 0xfffffe085a55d120
>> > trap() at trap+0x7ae/frame 0xfffffe085a55d330
>> > calltrap() at calltrap+0x8/frame 0xfffffe085a55d330
>> > --- trap 0x16, rip = 0xffffffff827dd3a9, rsp = 0xfffffe085a55d408, rbp = 0xfffffe085a55d430 ---
>> > g_pLogger() at 0xffffffff827dd3a9/frame 0xfffffe085a55d430
>> > g_pLogger() at 0xffffffff8274e5c7/frame 0x3
>> > KDB: enter: panic
>> > 
>> > Since g_pLogger is a symbol in vboxdrv.ko, it looks like virtualbox is
>> > the trigger.
>> > 
>> > There are no symbols for the virtualbox kmods, possibly because I
>> > installed them as an upgrade using packages (built with the same source
>> > tree version) instead of by using PORTS_MODULES in make.conf, so ports
>> > kgdb didn't have anything useful to say about what happened before the
>> > trap.
>> > 
>> > This panic is very repeatable.  I just got another one when starting the
>> > same VM., but this time the two calls before the trap were
>> > null_bug_bypass().  Hmn, that symbol is in nullfs ...
>> > 
>> > I don't see this with a Windows 7 VM.
>> > 
>> > All of the virtualbox kmod files are compiled with -mno-mmx -mno-sse
>> > -msoft-float -mno-aes -mno-avx
> Your disassemble listed fxrstor instruction that failing, or did I
> mis-remembered ? This is most likely some context switch code, either
> by virtual machine or erronously executed guest code. It is not a
> spontaneous use of FPU, but more likely something different. Can you
> confirm ?
> 
> In either case, I do not remember any KBI changes around PCB layout or
> fpu_enter() KPI recently.
> 
>> 
>> I suspect head packages are quite likely built against the a "wrong" KBI
>> and are too fragile to use for kmods vs compiling from ports. :-/  I would
>> try a built-from-ports kmod to see if the panics go away.
> 
> FWIW, I will commit the following change shortly. Since third-party
> modules break the invariant, either due to bugs (ndis wrappers) or
> possibly due to KBI breakage, it is worth to have the detection enabled
> for production kernels.

Interesting ... I tried running virtualbox on recent 10.3-STABLE with a
GENERIC kernel and the guest seemed to operate properly.  Then I enabled
INVARIANTS and got the panic.  I suspect that is why nobody has stumbled
across this before.