panic: Unregistered use of FPU in kernel

[Konstantin Belousov]

On Thu, Sep 26, 2019 at 11:20:51AM -0600, Alan Somers wrote:
> On Thu, Sep 26, 2019 at 11:02 AM Konstantin Belousov <kostikbel at gmail.com>
> wrote:
> 
> > On Thu, Sep 26, 2019 at 09:45:43AM -0600, Alan Somers wrote:
> > > The latest VM snapshot
> > (FreeBSD-13.0-CURRENT-amd64-20190920-r352544.qcow2)
> > > instapanics on boot:
> > >
> > > panic: Unregistered use of FPU in kernel
> > >
> > > stack trace:
> > > ...
> > > sse42_crc32c
> > > readsuper
> > > ffs_sbget
> > > g_label_ufs_taste_common
> > > g_label_taste
> > > g_new_provider_event
> > > g_run_events
> > > fork_exit
> > > ...
> > >
> > > Has anybody touched this area recently?  I'll try to narrow down the
> > commit
> > > range.
> >
> > Start with disassembling the faulting instruction.  I suspect that somehow
> > vital compiler switches like -mno-sse got omitted in the build.
> >
> 
> No problem with compiler switches here.  The C file uses inline assembly to
> generate a crc32q instruction, in crc32_sse42.c:257.  But why would that
> generate a floating point exception?  The instruction doesn't appear to be
> using any floating point registers.  This is on a Kaby Lake CPU.
> 
> crc32q %rsi, %rbx

No idea, this instruction does not generate #NP at all.

Provide exact script of the panic and backtrace,
together with the disassembly of the function which contained the faulted
instruction.  Do disassemble from ddb, in case text was corrupted.