Re: panic booting with if_tap_load="YES" in loader.conf

On Sat, May 18, 2019 at 10:24:36AM -0400, Mark Johnston wrote:
> On Sat, May 18, 2019 at 11:55:46AM +0300, Konstantin Belousov wrote:
> > On Sat, May 18, 2019 at 01:33:28AM -0400, Mark Johnston wrote:
> > > On Fri, May 17, 2019 at 10:18:57PM -0600, Rebecca Cran wrote:
> > > > I just updated from r346856 to r347950 and ran into a new panic, caused
> > > > by having if_tap_load="YES" in /boot/loader.conf - because it's already
> > > > built-in to the kernel:
> > > 
> > > I think this patch should fix the panic, but I only compile-tested it.
> > > I considered having the logic live in preload_delete_name() instead, but
> > > the boot-time ucode code must still defer the deletion somewhat.
> > 
> > Try this instead.  I will revert r347931 after this landed, or could keep
> > it alone.
> 
> I have no strong feeling either way.
> 
> > diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
> > index 1cf09dc5cb7..03fe8a5d096 100644
> > --- a/sys/amd64/amd64/machdep.c
> > +++ b/sys/amd64/amd64/machdep.c
> > _at__at_ -1616,6 +1616,13 _at__at_ hammer_time(u_int64_t modulep, u_int64_t physfree)
> >  	bzero((void *)thread0.td_kstack, kstack0_sz);
> >  	physfree += kstack0_sz;
> >  
> > +	/*
> > +	 * Initialize enough of thread0 for delayed invalidation to
> > +	 * work very early.  Rely on thread0.td_base_pri
> > +	 * zero-initialization, it is reset to PVM at proc0_init().
> > +	 */
> > +	pmap_thread_init_invl_gen(&thread0);
> > +
> 
> I think pmap_thread_init_invl_gen() also needs to initialize
> invl_gen->saved_pri to 0.
It is zero-initialized, same as td_base_pri. The call to
pmap_thread_init_invl_gen() is needed because _INVALID bit must be set,
which is cleared by default.