Fatal trap 12: page fault on Acer Chromebook 720 (peppy)

[Konstantin Belousov]

On Fri, Aug 17, 2018 at 10:02:08AM +0100, John Baldwin wrote:
> On 8/17/18 9:54 AM, Michael Gmelin wrote:
> > 
> > 
> >> On 17. Aug 2018, at 08:17, John Baldwin <jhb at FreeBSD.org> wrote:
> >>
> >>> On 8/16/18 1:58 PM, Michael Gmelin wrote:
> >>>
> >>>
> >>>> On 15. Aug 2018, at 15:55, Konstantin Belousov <kostikbel at gmail.com <mailto:kostikbel at gmail.com>> wrote:
> >>>>
> >>>>> On Wed, Aug 15, 2018 at 03:52:37PM +0200, Michael Gmelin wrote:
> >>>>>
> >>>>>
> >>>>>>> On 15. Aug 2018, at 15:04, Konstantin Belousov <kostikbel at gmail.com <mailto:kostikbel at gmail.com>> wrote:
> >>>>>>>
> >>>>>>> On Wed, Aug 15, 2018 at 12:51:06AM +0200, Michael Gmelin wrote:
> >>>>>>> Reviving this old thread, since I just updated to r337818 and a similar
> >>>>>>> problem is happening again. Since the fix in r334799 (review
> >>>>>>> https://reviews.freebsd.org/D15675) (mp_)machdep.c have been touched,
> >>>>>>> so maybe this is related
> >>>>>>> (https://svnweb.freebsd.org/base?view=revision&revision=334799).
> >>>>>>>
> >>>>>>> Please see the screenshot of the panic below:
> >>>>>>> https://gist.github.com/grembo/78d0f2a100dd4f16775b85a118769658
> >>>>>>>
> >>>>>>> This is me not digging any deeper, hoping that this is something
> >>>>>>> obvious. Please let me know if you need more input.
> >>>>>>
> >>>>>> I do not see how recent mp_machdep.c changes could affect this.
> >>>>>> Can you try newest kernel but old loader ?
> >>>>>
> >>>>> I will try (but that will take a while). Oh, also, it still boots in save mode/with smp disabled.
> >>>>
> >>>> Right, this is because the access to that address through DMAP is only
> >>>> needed when configuring AP startup resources.
> >>>>
> >>>> Also, I think it is safe to suggest that the bisect is needed.
> >>>
> >>> Using an older loader didn???t help, but I identified the problem:
> >>>
> >>> https://svnweb.freebsd.org/base?view=revision&revision=334952
> >>>
> >>> modified the code you introduced in
> >>>
> >>> https://svnweb.freebsd.org/base?view=revision&revision=334799
> >>>
> >>> By correcting units to pages it also broke booting the Chromebook as a side effect - so the previous fix just worked due to a bug it seems.
> >>>
> >>> Is there an easy way to output the content of physmap at that point (debug.late_console=0 doesn???t work) - like an existing buffer I could use, or would this be more elaborate (I did something complicated last time but didn???t save it, so any simple solution would be preferred).
> >>
> >> How about reverting the commit for now so you get a working console
> >> and print out the physmap array values along with Maxmem later in
> >> the boot (or just use kgdb to examine them once the system is running)?
> >>
> > 
> > This is before the system has a working console (part of calling getmem...), disabling late console makes it hang, physmap changes afterwards, so running kgdb later doesn???t help. Last time I kept a copy of physmap and logged it later to know the original content. I can do that again, I just thought maybe there is a simple mechanism I???m not aware of that would save me some time.
> 
> I thought we only modified phys_avail[], but saving a copy of physmap[] and
> dumping it from kgdb is probably the simplest thing to do.
UP boot works ?