Re: CHANGE_PV_LIST_LOCK_TO_PHYS is not correct when !NUMA ?

On Fri, May 08, 2020 at 06:53:24PM +0300, Andriy Gapon wrote:
> 
> I have a reproducible panic with a custom kernel without option NUMA while using
> amdgpu driver from linuxkpi-based drm:
> 
> panic: address 41ec00000 beyond the last segment
> 
> I did some quick debugging and the panic happens when Xorg server tries to
> access a frame buffer (or something like that).  There is a page fault that gets
> satisfied by ttm with a fictitious page.
> 
> The stack trace is:
> #11 0xffffffff808031a3 in panic (fmt=0xffffffff8119a998 <cnputs_mtx>
> "5\003ʀ\377\377\377\377") at /usr/devel/git/motil/sys/kern/kern_shutdown.c:839
> #12 0xffffffff80bbc552 in pmap_enter (pmap=<optimized out>, va=34504441856,
> m=<optimized out>, prot=<optimized out>, flags=<optimized out>, psind=<optimized
> out>) at /usr/devel/git/motil/sys/amd64/amd64/pmap.c:6035
> #13 0xffffffff80b288be in vm_fault_populate (fs=<optimized out>) at
> /usr/devel/git/motil/sys/vm/vm_fault.c:519
> #14 vm_fault_allocate (fs=<optimized out>) at
> /usr/devel/git/motil/sys/vm/vm_fault.c:1032
> #15 vm_fault (map=<optimized out>, vaddr=<optimized out>, fault_type=<optimized
> out>, fault_flags=<optimized out>, m_hold=<optimized out>) at
> /usr/devel/git/motil/sys/vm/vm_fault.c:1342
> #16 0xffffffff80b26e7e in vm_fault_trap (map=0xfffffe0017cd39e8,
> vaddr=<optimized out>, fault_type=<optimized out>, fault_flags=0,
> signo=0xfffffe00a810dbc4, ucode=0xfffffe00a810dbc0) at
> /usr/devel/git/motil/sys/vm/vm_fault.c:589
> #17 0xffffffff80bcf89c in trap_pfault (frame=0xfffffe00a810dc00,
> usermode=<optimized out>, signo=<optimized out>, ucode=0xffffffff80853250
> <putchar>) at /usr/devel/git/motil/sys/amd64/amd64/trap.c:821
> #18 0xffffffff80bceeec in trap (frame=0xfffffe00a810dc00) at
> /usr/devel/git/motil/sys/amd64/amd64/trap.c:34
> 
> 
> The line number in pmap_enter() is incorrect, I guess because of optimizations.
> The assert seems to be reached via pmap_enter -> CHANGE_PV_LIST_LOCK_TO_PHYS ->
> PHYS_TO_PV_LIST_LOCK -> pa_index().
> 
> The panic in correct in that the page is fictitious and its physical address is
> beyond the end of real physical memory.
> It seems that NUMA PHYS_TO_PV_LIST_LOCK() is aware of such pages, but !NUMA one
> is not.

I think you can remove this assert.  pa_index() is always taken by
% NVP_LIST_LOCKS, because fictitious mappings are not promoted.

Try that and commit if it works for you.