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

[Kyle Evans]

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.