Date: Sat, 9 May 2020 18:52:24 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: CHANGE_PV_LIST_LOCK_TO_PHYS is not correct when !NUMA ? Message-ID: <6485ab77-a3d0-8916-9431-74e4da1e3ea7@FreeBSD.org> In-Reply-To: <20200508161500.GC44519@kib.kiev.ua> References: <0d7db402-621e-cc6b-2918-2078f63e2a9b@FreeBSD.org> <20200508161500.GC44519@kib.kiev.ua>
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On 08/05/2020 19:15, Konstantin Belousov wrote:
> 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.
I tried this change:
diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index 4deed86a76d1a..b834b7f0388b7 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -345,7 +345,7 @@ pmap_pku_mask_bit(pmap_t pmap)
#define NPV_LIST_LOCKS MAXCPU
#define PHYS_TO_PV_LIST_LOCK(pa) \
- (&pv_list_locks[pa_index(pa) % NPV_LIST_LOCKS])
+ (&pv_list_locks[((pa) >> PDRSHIFT) % NPV_LIST_LOCKS])
#endif
#define CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, pa) do { \
It fixed the original problem, but I got a new panic.
"DI already started" in pmap_remove() -> pmap_delayed_invl_start_u().
I guess that !NUMA variant does not get much testing, so I'll probably just
stick with the default.
--
Andriy Gapon
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