arm SMP on Cortex-A15
Wojciech Macek
wma at semihalf.com
Thu Mar 27 14:25:09 UTC 2014
Sorry, I meant
https://drive.google.com/file/d/0B-7yTLrPxaWtRjJvTzJZY3g5akU/edit?usp=sharing
W.
2014-03-27 14:10 GMT+01:00 Wojciech Macek <wma at semihalf.com>:
> I started cleaning up and have some concerns. Sorry guys, the r263251
> still looks like a workaround to me :)
> The fact that TLB cache issue is seen only on executable pages and that
> Olivier's fix helps suggests, that we are missing flush-I somewhere (crash
> appears only when deallocating userspace vm, so my guess is pmap_kremove,
> where definitely should be flushID). For test purposes I reverted r263251
> and added additional flushID/flushD logic to the pmap-v6 in
> performance-critical sections, or modified flushD to flushID where the
> speed is not the case. All changes integrated with previous patches can be
> found here:
>
> https://drive.google.com/file/d/0B-7yTLrPxaWtRFRHTUtpZ3VKbG8/edit?usp=sharing
> With above patch I'm able to run all tests without any problems.
>
> Maybe it would be better to fix these suspicious places in pmap instead?
>
> Regards,
> Wojtek
>
>
> 2014-03-25 14:35 GMT+01:00 Ian Lepore <ian at freebsd.org>:
>
> Good, that means we can stop searching for the missing tlb flush when a
>> pte is invalidated. :) You guys can commit whenever you're ready (or I
>> can do it if you'd like).
>>
>> -- Ian
>>
>> On Tue, 2014-03-25 at 11:14 +0100, Wojciech Macek wrote:
>> > Hi Ian,
>> >
>> > The r263251 fix helped, thanks!
>> > So now, if you don';t have any objections, I will clean up a little the
>> > cpufunc.S & pmap-v6 changes and make them ready for submitting.
>> >
>> > Regards,
>> > Wojtek
>> >
>> >
>> > 2014-03-24 14:31 GMT+01:00 Wojciech Macek <wma at semihalf.com>:
>> >
>> > > Without the unconditional invalidation, the panic shows up just at the
>> > > beginning, after rootfs is mounted and init scripts are running. When
>> a
>> > > userspace process is exitting, its memory resources are freed - this
>> is the
>> > > moment pmap_remove_pages fails due to tharanslation fault. It is the
>> > > "typical" crash I observed when TLB-cache holds an old entry. Below
>> there
>> > > is a backtrace, but I doubt if it can be helpful.
>> > >
>> > > Regarding old pte/tlb, the TLB cache contains entry from old process
>> > > context, when in-memory-PTE value is already correct - at least this
>> was
>> > > the scenario when I debugged it last year. So, invalidating after
>> *pte=0 is
>> > > definitely not our case. The issue shows up only on a15, where the
>> > > tlb-prefetcher can cache pte entries anytime.
>> > >
>> > > I believe I don't have r263251 integrated. I'll give it a try -
>> typically,
>> > > the tlb-caused crash appears only on pages containing shared
>> libraries code
>> > > (with executable attr), so there is a chance Olivier's fix help.
>> > >
>> > >
>> > > The fault:
>> > >
>> > > vm_fault(0xc5b894f0, 0, 2, 0) -> 1
>> > > Fatal kernel mode data abort: 'Translation Fault (P)'
>> > > trapframe: 0xef2cca40
>> > > FSR=00000817, FAR=00000030, spsr=60000013
>> > > r0 =00000000, r1 =c320a048, r2 =00000000, r3 =c3208074
>> > > r4 =c5b7cd08, r5 =c5b7cd04, r6 =c5b05800, r7 =c5b895ac
>> > > r8 =c320a044, r9 =fffffffe, r10=c5b895ac, r11=ef2ccae0
>> > > r12=00000000, ssp=ef2cca90, slr=c0604148, pc =c0628a60
>> > >
>> > > [ thread pid 83 tid 100050 ]
>> > > Stopped at pmap_remove_pages+0x270: streq r3, [r0,
>> #0x030]
>> > > db> bt
>> > > Tracing pid 83 tid 100050 td 0xc5bc4320
>> > > db_trace_self() at db_trace_self
>> > > pc = 0xc061f62c lr = 0xc024ddbc (db_hex2dec+0x498)
>> > > sp = 0xef2cc738 fp = 0xef2cc750
>> > > r10 = 0xc0708270
>> > > db_hex2dec() at db_hex2dec+0x498
>> > > pc = 0xc024ddbc lr = 0xc024d76c (db_command_loop+0x2f0)
>> > > sp = 0xef2cc758 fp = 0xef2cc7f8
>> > > r4 = 0x00000000 r5 = 0x00000000
>> > > r6 = 0xc0695cf1
>> > > db_command_loop() at db_command_loop+0x2f0
>> > > pc = 0xc024d76c lr = 0xc024d4dc (db_command_loop+0x60)
>> > > sp = 0xef2cc800 fp = 0xef2cc810
>> > > r4 = 0xc0666f88 r5 = 0xc067b997
>> > > r6 = 0xc0752954 r7 = 0xc0748f80
>> > > r8 = 0xef2cca40 r9 = 0xc07084e0
>> > > r10 = 0xc0748f84
>> > > db_command_loop() at db_command_loop+0x60
>> > > pc = 0xc024d4dc lr = 0xc024ffb8 (X_db_symbol_values+0x254)
>> > > sp = 0xef2cc818 fp = 0xef2cc938
>> > > r4 = 0x00000000 r5 = 0xef2cc820
>> > > r6 = 0xc0748fb0
>> > > X_db_symbol_values() at X_db_symbol_values+0x254
>> > > pc = 0xc024ffb8 lr = 0xc0430554 (kdb_trap+0x164)
>> > > sp = 0xef2cc940 fp = 0xef2cc968
>> > > r4 = 0x00000000 r5 = 0x00000817
>> > > r6 = 0xc0748fb0 r7 = 0xc0748f80
>> > > kdb_trap() at kdb_trap+0x164
>> > > pc = 0xc0430554 lr = 0xc0632ef0 (data_abort_handler+0x7dc)
>> > > sp = 0xef2cc970 fp = 0xef2cc988
>> > > r4 = 0xef2cca40 r5 = 0x600000d3
>> > > r6 = 0x00000030 r7 = 0x00000817
>> > > r8 = 0xc5b894f0 r9 = 0x00000001
>> > > r10 = 0xef2cca40
>> > > data_abort_handler() at data_abort_handler+0x7dc
>> > > pc = 0xc0632ef0 lr = 0xc0632cc0 (data_abort_handler+0x5ac)
>> > > sp = 0xef2cc990 fp = 0xef2cca38
>> > > r4 = 0x00000817 r5 = 0xc5bc4320
>> > > r6 = 0xc5a47a0c r7 = 0x00000004
>> > > data_abort_handler() at data_abort_handler+0x5ac
>> > > pc = 0xc0632cc0 lr = 0xc0621214 (exception_exit)
>> > > sp = 0xef2cca40 fp = 0xef2ccae0
>> > > r4 = 0xc5b7cd08 r5 = 0xc5b7cd04
>> > > r6 = 0xc5b05800 r7 = 0xc5b895ac
>> > > r8 = 0xc320a044 r9 = 0xfffffffe
>> > > r10 = 0xc5b895ac
>> > > exception_exit() at exception_exit
>> > > pc = 0xc0621214 lr = 0xc0604148 (PHYS_TO_VM_PAGE+0x48)
>> > > sp = 0xef2cca94 fp = 0xef2ccae0
>> > > r0 = 0x00000000 r1 = 0xc320a048
>> > > r2 = 0x00000000 r3 = 0xc3208074
>> > > r4 = 0xc5b7cd08 r5 = 0xc5b7cd04
>> > > r6 = 0xc5b05800 r7 = 0xc5b895ac
>> > > r8 = 0xc320a044 r9 = 0xfffffffe
>> > > r10 = 0xc5b895ac r12 = 0x00000000
>> > > pmap_remove_pages() at pmap_remove_pages+0x270
>> > > pc = 0xc0628a60 lr = 0xc05f2d08 (vmspace_exit+0xd8)
>> > > sp = 0xef2ccae8 fp = 0xef2ccb10
>> > > r4 = 0xc5b895a8 r5 = 0xc5bc4320
>> > > r6 = 0x00000001 r7 = 0xc5a47960
>> > > r8 = 0xc5b895ac r9 = 0xc5b894f0
>> > > r10 = 0xc0753be0
>> > > vmspace_exit() at vmspace_exit+0xd8
>> > > pc = 0xc05f2d08 lr = 0xc03a7348 (exit1+0x930)
>> > > sp = 0xef2ccb18 fp = 0xef2ccb70
>> > > r4 = 0xc5a479fc r5 = 0x00000004
>> > > r6 = 0xc583861c r7 = 0x00000001
>> > > r8 = 0xc5a47960 r9 = 0xc5bc4320
>> > > r10 = 0xc5a47a0c
>> > > exit1() at exit1+0x930
>> > > pc = 0xc03a7348 lr = 0xc03f1604 (sigexit+0x8c4)
>> > > sp = 0xef2ccb78 fp = 0xef2ccd68
>> > > r4 = 0x00000002 r5 = 0xc5bc4320
>> > > r6 = 0xc5a47960 r7 = 0xc5a47a0c
>> > > r8 = 0xc5bc4320 r9 = 0xc5b7a000
>> > > r10 = 0x00000002
>> > > sigexit() at sigexit+0x8c4
>> > > pc = 0xc03f1604 lr = 0xc03f23a0 (postsig+0x39c)
>> > > sp = 0xef2ccd70 fp = 0xef2cce18
>> > > r4 = 0x00000001 r5 = 0xc5bc4320
>> > > r6 = 0xc5a47960 r7 = 0xc5b7aab8
>> > > r8 = 0xc5a47a0c r9 = 0xc5b7a000
>> > > r10 = 0x00000002
>> > > postsig() at postsig+0x39c
>> > > pc = 0xc03f23a0 lr = 0xc044388c (ast+0x4f4)
>> > > sp = 0xef2cce20 fp = 0xef2cce58
>> > > r4 = 0x00000001 r5 = 0xc5bc4320
>> > > r6 = 0xc5a47960 r7 = 0xc5a47a0c
>> > > r8 = 0xc5a47a0c r9 = 0x01020804
>> > > r10 = 0x00000ab8
>> > > ast() at ast+0x4f4
>> > > pc = 0xc044388c lr = 0xc0621080 (swi_entry+0x6c)
>> > > sp = 0xef2cce60 fp = 0xbfffe438
>> > > r4 = 0x40000013 r5 = 0xc5bc4320
>> > > r6 = 0x00000001 r7 = 0x00000154
>> > > r8 = 0x20037008 r9 = 0xbfffee5c
>> > > r10 = 0xbfffea10
>> > > swi_entry() at swi_entry+0x6c
>> > > pc = 0xc0621080 lr = 0xc0621080 (swi_entry+0x6c)
>> > > sp = 0xef2cce60 fp = 0xbfffe438
>> > > Unable to unwind further
>> > > db>
>> > >
>> > >
>> > >
>> > > 2014-03-22 14:20 GMT+01:00 Ian Lepore <ian at freebsd.org>:
>> > >
>> > > On Fri, 2014-03-21 at 07:20 +0100, Wojciech Macek wrote:
>> > >> > No, changing flushD to flushID did not make any difference, but I
>> think
>> > >> it
>> > >> > should be there - D-only flushing might not be sufficient.
>> > >> >
>> > >>
>> > >> Olivier reminded me right after I posted that: last week I made a
>> change
>> > >> to cpufunc.c that makes flushD and flushID the same. So of course it
>> > >> made no difference. :) It really should be flushID though, in case
>> > >> that ever changes.
>> > >>
>> > >> You didn't say whether you have that change, which was r263251.
>> > >>
>> > >> > Currently, I'm running pmap_kernel_internal attached below. It is
>> doing
>> > >> > unconditional flushID at the end, just like the old comment was
>> saying
>> > >> :)
>> > >> > SMP seems to be stable.
>> > >> >
>> > >>
>> > >> That seems to say that somehow there is a valid TLB entry even though
>> > >> the old pte for that entry is zero. That means there's a problem
>> > >> somewhere else in the code, but I don't see it. It looks to me like
>> we
>> > >> do a TLB flush everywhere that we zero out a pte.
>> > >>
>> > >> You said without the unconditional flush it panics at startup.
>> Where in
>> > >> startup? Early, or after init is launched or what? Where does the
>> > >> panic backtrace to?
>> > >>
>> > >> If we've got some other pte/tlb maintenance problem, I'd hate to
>> hide it
>> > >> with this unconditional flush and have it appear as some other
>> problem
>> > >> later that will be even harder to track down.
>> > >>
>> > >> -- Ian
>> > >>
>> > >>
>> > >>
>> > >
>>
>>
>>
>
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