Re: panic: mutex pmap not owned at ... efirt_machdep.c:255

On Sat, Aug 04, 2018 at 08:56:58AM -0500, Kyle Evans wrote:
> On Sat, Aug 4, 2018 at 8:13 AM, Konstantin Belousov <kostikbel_at_gmail.com> wrote:
> > On Sat, Aug 04, 2018 at 08:05:24AM -0500, Kyle Evans wrote:
> >> On Sat, Aug 4, 2018 at 3:37 AM, Konstantin Belousov <kostikbel_at_gmail.com> wrote:
> >> > On Fri, Aug 03, 2018 at 11:27:02PM -0500, Kyle Evans wrote:
> >> >>
> >> >> This seems odd- pmap lock is acquired at [1], then asserted shortly
> >> >> later at [2]... I avoid some of this stuff as well as I can, but is it
> >> >> actually possible for PCPU_GET(...) acquired curpmap to not match
> >> >> curthread->td_proc->p_vmspace->vm_pmap in this context?
> >> >>
> >> >> [1] https://svnweb.freebsd.org/base/head/sys/dev/efidev/efirt.c?view=markup#l260
> >> >> [2] https://svnweb.freebsd.org/base/head/sys/amd64/amd64/efirt_machdep.c?view=markup#l254
> >> > There could be that curpcpu not yet synced with proc0 pmap.  It could be
> >> > fixed.
> >> >
> >> > But it is not clear to me why efi_arch_enter() is called there.  I see
> >> > the check for GetTime belonging to the range described by a map descriptor.
> >> > I do not see why do you need an enter into the EFI context for comparing
> >> > integers.
> >>
> >> This probably could have been documented better, but efi_runtime
> >> pointer may (always?) point into runtime service memory that isn't
> >> valid/available at that point, so we get a fault and panic when
> >> dereferencing it to grab rt_gettime address. We ran into this wall
> >> when adding the check originally.
> > Wouldn't it be enough to access it by translating physical address into
> > DMAP ?
> 
> Ah, sure, sure. [1] is proper form, yeah?
> 
> [1] https://people.freebsd.org/~kevans/efi-dmap.diff

I would brace it with #ifdef PHYS_TO_DMAP, #error otherwise.
Also, it might make sense to check against dmaplimit as well (on arm64
it is called PHYS_IN_DMAP(), sight).

So it might make sense to define MD function in arch/efirt_machdep.c
to translate table' address into the KVA.