Re: [Qemu-devel] tcg/tcg.c:1892: tcg fatal error

[Artyom Tarasenko]

On Sun, Apr 10, 2011 at 8:52 PM, Igor Kovalenko
<address@hidden> wrote:
> On Sun, Apr 10, 2011 at 10:35 PM, Artyom Tarasenko <address@hidden> wrote:
>> On Sun, Apr 10, 2011 at 7:57 PM, Blue Swirl <address@hidden> wrote:
>>> On Sun, Apr 10, 2011 at 8:48 PM, Artyom Tarasenko <address@hidden> wrote:
>>>> On Sun, Apr 10, 2011 at 4:44 PM, Blue Swirl <address@hidden> wrote:
>>>>> On Sun, Apr 10, 2011 at 5:09 PM, Artyom Tarasenko <address@hidden> wrote:
>>>>>> On Sun, Apr 10, 2011 at 3:24 PM, Aurelien Jarno <address@hidden> wrote:
>>>>>>> On Sun, Apr 10, 2011 at 02:29:59PM +0200, Artyom Tarasenko wrote:
>>>>>>>> Trying to boot some proprietary OS I get qemu-system-sparc64 crash 
>>>>>>>> with a
>>>>>>>>
>>>>>>>> tcg/tcg.c:1892: tcg fatal error
>>>>>>>>
>>>>>>>> error message.
>>>>>>>>
>>>>>>>> It looks like it can be a platform independent bug though, because
>>>>>>>> when a '-singlestep' option IS present, qemu doesn't crash and seems
>>>>>>>> to translate the code properly.
>>>>>>>>
>>>>>>>> (gdb) bt
>>>>>>>> #0  0x00000032c2e327f5 in raise () from /lib64/libc.so.6
>>>>>>>> #1  0x00000032c2e33fd5 in abort () from /lib64/libc.so.6
>>>>>>>> #2  0x000000000051933d in tcg_reg_alloc_call (s=<value optimized out>,
>>>>>>>> def=0x89d340, opc=INDEX_op_call, args=0x10acc98, dead_iargs=3) at
>>>>>>>> qemu/tcg/tcg.c:1892
>>>>>>>> #3  0x000000000051a557 in tcg_gen_code_common (s=0x10b8940,
>>>>>>>> gen_code_buf=0x40338b60 "address@hidden 3\355I\211\256\220") at
>>>>>>>> qemu/tcg/tcg.c:2099
>>>>>>>> #4  tcg_gen_code (s=0x10b8940, gen_code_buf=0x40338b60 "address@hidden
>>>>>>>> 3\355I\211\256\220") at qemu/tcg/tcg.c:2142
>>>>>>>> #5  0x00000000004d38f1 in cpu_sparc_gen_code (env=0x10cce10,
>>>>>>>> tb=0x7fffe91bc218, gen_code_size_ptr=0x7fffffffd9b4) at
>>>>>>>> qemu/translate-all.c:93
>>>>>>>> #6  0x00000000004d1fd7 in tb_gen_code (env=0x10cce10, pc=18868776,
>>>>>>>> cs_base=18868780, flags=15, cflags=0) at qemu/exec.c:989
>>>>>>>> #7  0x00000000004d4029 in tb_find_slow (env1=<value optimized out>) at
>>>>>>>> qemu/cpu-exec.c:167
>>>>>>>> #8  tb_find_fast (env1=<value optimized out>) at cpu-exec.c:194
>>>>>>>> #9  cpu_sparc_exec (env1=<value optimized out>) at qemu/cpu-exec.c:556
>>>>>>>> #10 0x0000000000408868 in tcg_cpu_exec () at qemu/cpus.c:1066
>>>>>>>> #11 cpu_exec_all () at qemu/cpus.c:1102
>>>>>>>> #12 0x000000000053c756 in main_loop (argc=<value optimized out>,
>>>>>>>> argv=<value optimized out>, envp=<value optimized out>) at
>>>>>>>> qemu/vl.c:1430
>>>>>>>>
>>>>>>>> I inspected ts->val_type causing the abort() case and it turned out to 
>>>>>>>> be 0.
>>>>>>>>
>>>>>>>> The last lines of qemu.log (without -singlestep)
>>>>>>>> IN:
>>>>>>>> 0x00000000011fe9f0:  rdpr  %pstate, %g1
>>>>>>>> 0x00000000011fe9f4:  wrpr  %g1, 2, %pstate
>>>>>>>> --------------
>>>>>>>> IN:
>>>>>>>> 0x00000000011fe9f8:  ldub  [ %o0 ], %o1
>>>>>>>> 0x00000000011fe9fc:  mov  %o1, %o2
>>>>>>>> 0x00000000011fea00:  rdpr  %tick, %o3
>>>>>>>> 0x00000000011fea04:  cmp  %o1, %o2
>>>>>>>> 0x00000000011fea08:  be  %icc, 0x11fea00
>>>>>>>> 0x00000000011fea0c:  ldub  [ %o0 ], %o2
>>>>>>>>
>>>>>>>> Search PC...
>>>>>>>> Search PC...
>>>>>>>> Search PC...
>>>>>>>> Search PC...
>>>>>>>> Search PC...
>>>>>>>> Search PC...
>>>>>>>> --------------
>>>>>>>> IN:
>>>>>>>> 0x00000000011fe9f8:  ldub  [ %o0 ], %o1
>>>>>>>> 0x00000000011fe9fc:  mov  %o1, %o2
>>>>>>>> 0x00000000011fea00:  rdpr  %tick, %o3
>>>>>>>> 0x00000000011fea04:  cmp  %o1, %o2
>>>>>>>> 0x00000000011fea08:  be  %icc, 0x11fea00
>>>>>>>> 0x00000000011fea0c:  ldub  [ %o0 ], %o2
>>>>>>>>
>>>>>>>> 110521: Data Access MMU Miss (v=0068) pc=00000000011fe9f8
>>>>>>>> npc=00000000011fe9fc SP=000000000180ae41
>>>>>>>> pc: 00000000011fe9f8  npc: 00000000011fe9fc
>>>>>>>>
>>>>>>>> IN:
>>>>>>>> 0x00000000011fea00:  rdpr  %tick, %o3
>>>>>>>> 0x00000000011fea04:  cmp  %o1, %o2
>>>>>>>> 0x00000000011fea08:  be  %icc, 0x11fea00
>>>>>>>> 0x00000000011fea0c:  ldub  [ %o0 ], %o2
>>>>>>>> --------------
>>>>>>>> IN:
>>>>>>>> 0x00000000011fea10:  brz,pn   %o2, 0x11fe9f8
>>>>>>>> 0x00000000011fea14:  mov  %o2, %o4
>>>>>>>> --------------
>>>>>>>> IN:
>>>>>>>> 0x00000000011fea18:  rdpr  %tick, %o5
>>>>>>>> 0x00000000011fea1c:  cmp  %o2, %o4
>>>>>>>> 0x00000000011fea20:  be  %icc, 0x11fea18
>>>>>>>> 0x00000000011fea24:  ldub  [ %o0 ], %o4
>>>>>>>> --------------
>>>>>>>> IN:
>>>>>>>> 0x00000000011fea28:  brz,pn   %o4, 0x11fe9f4
>>>>>>>> 0x00000000011fea2c:  wrpr  %g0, %g1, %pstate
>>>>>>>> <EOF>
>>>>>>>>
>>>>>>>> The crash is 100% reproducible and happens always on the same place,
>>>>>>>> so it's probably a pure TCG issue, not related on getting the
>>>>>>>> external/timer interrupts.
>>>>>>>>
>>>>>>>> Do you need any additional info?
>>>>>>>>
>>>>>>>
>>>>>>> What would be interesting would be to get the corresponding TCG code
>>>>>>> from qemu.log (-d op,op_opt).
>>>>>>
>>>>>>
>>>>>> OP:
>>>>>>  ---- 0x11fea28
>>>>>>  ld_i64 tmp6,regwptr,$0x20
>>>>>>  movi_i64 cond,$0x0
>>>>>>  movi_i64 tmp8,$0x0
>>>>>>  brcond_i64 tmp6,tmp8,ne,$0x0
>>>>>>  movi_i64 cond,$0x1
>>>>>>  set_label $0x0
>>>>>>
>>>>>>  ---- 0x11fea2c
>>>>>>  movi_i64 tmp7,$0x0
>>>>>>  xor_i64 tmp0,tmp7,g1
>>>>>>  movi_i64 pc,$0x11fea2c
>>>>>>  movi_i64 tmp8,$compute_psr
>>>>>>  call tmp8,$0x0,$0
>>>>>>  movi_i64 tmp8,$0x0
>>>>>>  brcond_i64 cond,tmp8,eq,$0x1
>>>>>>  movi_i64 npc,$0x11fe9f4
>>>>>>  br $0x2
>>>>>>  set_label $0x1
>>>>>>  movi_i64 npc,$0x11fea30
>>>>>>  set_label $0x2
>>>>>>  movi_i64 tmp8,$wrpstate
>>>>>>  call tmp8,$0x0,$0,tmp0
>>>>>>  mov_i64 pc,npc
>>>>>>  movi_i64 tmp8,$0x4
>>>>>>  add_i64 npc,npc,tmp8
>>>>>>  exit_tb $0x0
>>>>>>
>>>>>> OP after liveness analysis:
>>>>>>  ---- 0x11fea28
>>>>>>  ld_i64 tmp6,regwptr,$0x20
>>>>>>  movi_i64 cond,$0x0
>>>>>>  movi_i64 tmp8,$0x0
>>>>>>  brcond_i64 tmp6,tmp8,ne,$0x0
>>>>>>  movi_i64 cond,$0x1
>>>>>>  set_label $0x0
>>>>>>
>>>>>>  ---- 0x11fea2c
>>>>>>  nopn $0x2,$0x2
>>>>>>  nopn $0x3,$0x68,$0x3
>>>>>>  movi_i64 pc,$0x11fea2c
>>>>>>  movi_i64 tmp8,$compute_psr
>>>>>>  call tmp8,$0x0,$0
>>>>>>  movi_i64 tmp8,$0x0
>>>>>>  brcond_i64 cond,tmp8,eq,$0x1
>>>>>>  movi_i64 npc,$0x11fe9f4
>>>>>>  br $0x2
>>>>>>  set_label $0x1
>>>>>>  movi_i64 npc,$0x11fea30
>>>>>>  set_label $0x2
>>>>>>  movi_i64 tmp8,$wrpstate
>>>>>>  call tmp8,$0x0,$0,tmp0
>>>>>>  mov_i64 pc,npc
>>>>>>  movi_i64 tmp8,$0x4
>>>>>>  add_i64 npc,npc,tmp8
>>>>>>  exit_tb $0x0
>>>>>>  end
>>>>>>
>>>>>> Does it mean the last block is processed correctly and the crash
>>>>>> happens on the next instruction which doesn't make it to the log?
>>>>>> The next instruction would be a
>>>>>>
>>>>>> 0x00000000011fea30:  retl
>>>>>>
>>>>>> Since it's a branch instruction I guess this would also be a tcg block 
>>>>>> boundary.
>>>>>
>>>>> Because abort() was called from tcg_reg_alloc_call, I'd say 'retl'
>>>>> (synthetic op for 'jmpl %o8 + 8, %g0') was the problem.
>>>>
>>>> Any idea why? retl is not a rare instruction...
>>>
>>> Sorry, calls are generated for helpers, so it's not 'jmpl' but the
>>> call to wrpstate helper.
>>
>> And why it doesn't happen in a singlestep mode?
>> I tried to comment out
>> cpu_check_irqs(env);
>> in the helper_wrpstate but it made no difference. The only suspicious
>> thing left is register bank switching. Is it safe to switch register
>> banks in the helper function? Shouldn't we end the translation block
>> before?
>
> Not sure if I have seen write to pstate in delay slot, but switching
> globals with PS_AG appears to be safe.
> Do you know which bits are changed in the pstate?

Hard to say. With a breakpoint set qemu doesn't crash.
The breakpoint shows the change from 0x14->0x16.
So the only difference is that interrupts are getting enabled. No
register bank change.
(And now also no cpu_check_irqs(env) call, because I commented it out.)

But given there was a Data Access MMU Miss, I would expect there must
have beeb a PS_MG switch.

Also the breakpoint makes tcg to cut the translation block before the wrpr:

IN:
0x00000000011fea18:  rdpr  %tick, %o5
0x00000000011fea1c:  cmp  %o2, %o4
0x00000000011fea20:  be  %icc, 0x11fea18
0x00000000011fea24:  ldub  [ %o0 ], %o4
--------------
IN:
0x00000000011fea28:  brz,pn   %o4, 0x11fe9f4
--------------
IN:
0x00000000011fea2c:  wrpr  %g0, %g1, %pstate
--------------
IN:
0x00000000011fea30:  retl
--------------
IN:
0x00000000011fea30:  retl
0x00000000011fea34:  sub  %o5, %o3, %o0

-- 
Regards,
Artyom Tarasenko

solaris/sparc under qemu blog: http://tyom.blogspot.com/