[Qemu-devel] qemu-system-ppc TCG assert with git master

[Qemu-devel] qemu-system-ppc TCG assert with git master

[Mark Cave-Ayland]

Hi all,

Whilst testing git master in preparation for some OpenBIOS updates, I'm
seeing the following TCG assert in one of my older test images:


$ gdb --args ./qemu-system-ppc -cdrom
/home/build/src/qemu/image/ppc/ubuntu-5.10-live-powerpc.iso -boot d -g
800x600x8
GNU gdb (GDB) 7.4.1-debian
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/build/rel-qemu-git/bin/qemu-system-ppc...done.
(gdb) r
Starting program: /home/build/rel-qemu-git/bin/qemu-system-ppc -cdrom
/home/build/src/qemu/image/ppc/ubuntu-5.10-live-powerpc.iso -boot d -g
800x600x8
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7fffe9ef3700 (LWP 11437)]
[New Thread 0x7fffe5bf1700 (LWP 11438)]
[New Thread 0x7fffe53f0700 (LWP 11439)]
[Thread 0x7fffe5bf1700 (LWP 11438) exited]
[New Thread 0x7fffe5bf1700 (LWP 11443)]
[Thread 0x7fffe5bf1700 (LWP 11443) exited]
qemu-system-ppc: /home/build/src/qemu/git/qemu/tcg/optimize.c:212:
tcg_opt_gen_mov: Assertion `temps[src].state != TCG_TEMP_CONST' failed.

Program received signal SIGABRT, Aborted.
[Switching to Thread 0x7fffe53f0700 (LWP 11439)]
0x00007ffff22ec165 in *__GI_raise (sig=<optimized out>) at
../nptl/sysdeps/unix/sysv/linux/raise.c:64
64      ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0  0x00007ffff22ec165 in *__GI_raise (sig=<optimized out>) at
../nptl/sysdeps/unix/sysv/linux/raise.c:64
#1  0x00007ffff22ef3e0 in *__GI_abort () at abort.c:92
#2  0x00007ffff22e5311 in *__GI___assert_fail (assertion=0x555555a819e0
"temps[src].state != TCG_TEMP_CONST", file=<optimized out>, line=212,
function=0x555555a82460 "tcg_opt_gen_mov") at assert.c:81
#3  0x0000555555632701 in tcg_opt_gen_mov (s=0x555555f3bc80,
op=0x555555f82f00, args=0x555555f84350, old_op=INDEX_op_or_i32, dst=9,
src=189) at /home/build/src/qemu/git/qemu/tcg/optimize.c:212
#4  0x0000555555634e5c in tcg_constant_folding (s=0x555555f3bc80) at
/home/build/src/qemu/git/qemu/tcg/optimize.c:984
#5  0x0000555555636295 in tcg_optimize (s=0x555555f3bc80) at
/home/build/src/qemu/git/qemu/tcg/optimize.c:1356
#6  0x000055555562c30c in tcg_gen_code_common (s=0x555555f3bc80,
gen_code_buf=0x7fffe8840770 "", search_pc=-1) at
/home/build/src/qemu/git/qemu/tcg/tcg.c:2277
#7  0x000055555562c67a in tcg_gen_code (s=0x555555f3bc80,
gen_code_buf=0x7fffe8840770 "") at
/home/build/src/qemu/git/qemu/tcg/tcg.c:2385
#8  0x000055555561e068 in cpu_ppc_gen_code (env=0x7ffff7fdf260,
tb=0x7fffe65ead30, gen_code_size_ptr=0x7fffe53ef890) at
/home/build/src/qemu/git/qemu/translate-all.c:182
#9  0x000055555561f49c in tb_gen_code (cpu=0x7ffff7fd7010,
pc=3373291568, cs_base=0, flags=0, cflags=0) at
/home/build/src/qemu/git/qemu/translate-all.c:1064
#10 0x0000555555621403 in tb_find_slow (env=0x7ffff7fdf260,
pc=3373291568, cs_base=0, flags=0) at
/home/build/src/qemu/git/qemu/cpu-exec.c:299
#11 0x000055555562158c in tb_find_fast (env=0x7ffff7fdf260) at
/home/build/src/qemu/git/qemu/cpu-exec.c:327
#12 0x00005555556219dd in cpu_ppc_exec (env=0x7ffff7fdf260) at
/home/build/src/qemu/git/qemu/cpu-exec.c:485
#13 0x00005555556684e9 in tcg_cpu_exec (env=0x7ffff7fdf260) at
/home/build/src/qemu/git/qemu/cpus.c:1354
#14 0x0000555555668600 in tcg_exec_all () at
/home/build/src/qemu/git/qemu/cpus.c:1387
#15 0x0000555555667929 in qemu_tcg_cpu_thread_fn (arg=0x7ffff7fd7010) at
/home/build/src/qemu/git/qemu/cpus.c:1032
#16 0x00007ffff264bb50 in start_thread (arg=<optimized out>) at
pthread_create.c:304
#17 0x00007ffff239595d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#18 0x0000000000000000 in ?? ()
(gdb)


Any ideas? I can easily reproduce here if any further information is
required.


ATB,

Mark.

Re: [Qemu-devel] qemu-system-ppc TCG assert with git master

[Mark Cave-Ayland]

On 12/03/15 08:41, Mark Cave-Ayland wrote:

> Hi all,
> 
> Whilst testing git master in preparation for some OpenBIOS updates, I'm
> seeing the following TCG assert in one of my older test images:
> 
> 
> $ gdb --args ./qemu-system-ppc -cdrom
> /home/build/src/qemu/image/ppc/ubuntu-5.10-live-powerpc.iso -boot d -g
> 800x600x8
> GNU gdb (GDB) 7.4.1-debian
> Copyright (C) 2012 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later
> <http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
> and "show warranty" for details.
> This GDB was configured as "x86_64-linux-gnu".
> For bug reporting instructions, please see:
> <http://www.gnu.org/software/gdb/bugs/>...
> Reading symbols from /home/build/rel-qemu-git/bin/qemu-system-ppc...done.
> (gdb) r
> Starting program: /home/build/rel-qemu-git/bin/qemu-system-ppc -cdrom
> /home/build/src/qemu/image/ppc/ubuntu-5.10-live-powerpc.iso -boot d -g
> 800x600x8
> [Thread debugging using libthread_db enabled]
> Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
> [New Thread 0x7fffe9ef3700 (LWP 11437)]
> [New Thread 0x7fffe5bf1700 (LWP 11438)]
> [New Thread 0x7fffe53f0700 (LWP 11439)]
> [Thread 0x7fffe5bf1700 (LWP 11438) exited]
> [New Thread 0x7fffe5bf1700 (LWP 11443)]
> [Thread 0x7fffe5bf1700 (LWP 11443) exited]
> qemu-system-ppc: /home/build/src/qemu/git/qemu/tcg/optimize.c:212:
> tcg_opt_gen_mov: Assertion `temps[src].state != TCG_TEMP_CONST' failed.
> 
> Program received signal SIGABRT, Aborted.
> [Switching to Thread 0x7fffe53f0700 (LWP 11439)]
> 0x00007ffff22ec165 in *__GI_raise (sig=<optimized out>) at
> ../nptl/sysdeps/unix/sysv/linux/raise.c:64
> 64      ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.
> (gdb) bt
> #0  0x00007ffff22ec165 in *__GI_raise (sig=<optimized out>) at
> ../nptl/sysdeps/unix/sysv/linux/raise.c:64
> #1  0x00007ffff22ef3e0 in *__GI_abort () at abort.c:92
> #2  0x00007ffff22e5311 in *__GI___assert_fail (assertion=0x555555a819e0
> "temps[src].state != TCG_TEMP_CONST", file=<optimized out>, line=212,
> function=0x555555a82460 "tcg_opt_gen_mov") at assert.c:81
> #3  0x0000555555632701 in tcg_opt_gen_mov (s=0x555555f3bc80,
> op=0x555555f82f00, args=0x555555f84350, old_op=INDEX_op_or_i32, dst=9,
> src=189) at /home/build/src/qemu/git/qemu/tcg/optimize.c:212
> #4  0x0000555555634e5c in tcg_constant_folding (s=0x555555f3bc80) at
> /home/build/src/qemu/git/qemu/tcg/optimize.c:984
> #5  0x0000555555636295 in tcg_optimize (s=0x555555f3bc80) at
> /home/build/src/qemu/git/qemu/tcg/optimize.c:1356
> #6  0x000055555562c30c in tcg_gen_code_common (s=0x555555f3bc80,
> gen_code_buf=0x7fffe8840770 "", search_pc=-1) at
> /home/build/src/qemu/git/qemu/tcg/tcg.c:2277
> #7  0x000055555562c67a in tcg_gen_code (s=0x555555f3bc80,
> gen_code_buf=0x7fffe8840770 "") at
> /home/build/src/qemu/git/qemu/tcg/tcg.c:2385
> #8  0x000055555561e068 in cpu_ppc_gen_code (env=0x7ffff7fdf260,
> tb=0x7fffe65ead30, gen_code_size_ptr=0x7fffe53ef890) at
> /home/build/src/qemu/git/qemu/translate-all.c:182
> #9  0x000055555561f49c in tb_gen_code (cpu=0x7ffff7fd7010,
> pc=3373291568, cs_base=0, flags=0, cflags=0) at
> /home/build/src/qemu/git/qemu/translate-all.c:1064
> #10 0x0000555555621403 in tb_find_slow (env=0x7ffff7fdf260,
> pc=3373291568, cs_base=0, flags=0) at
> /home/build/src/qemu/git/qemu/cpu-exec.c:299
> #11 0x000055555562158c in tb_find_fast (env=0x7ffff7fdf260) at
> /home/build/src/qemu/git/qemu/cpu-exec.c:327
> #12 0x00005555556219dd in cpu_ppc_exec (env=0x7ffff7fdf260) at
> /home/build/src/qemu/git/qemu/cpu-exec.c:485
> #13 0x00005555556684e9 in tcg_cpu_exec (env=0x7ffff7fdf260) at
> /home/build/src/qemu/git/qemu/cpus.c:1354
> #14 0x0000555555668600 in tcg_exec_all () at
> /home/build/src/qemu/git/qemu/cpus.c:1387
> #15 0x0000555555667929 in qemu_tcg_cpu_thread_fn (arg=0x7ffff7fd7010) at
> /home/build/src/qemu/git/qemu/cpus.c:1032
> #16 0x00007ffff264bb50 in start_thread (arg=<optimized out>) at
> pthread_create.c:304
> #17 0x00007ffff239595d in clone () at
> ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
> #18 0x0000000000000000 in ?? ()
> (gdb)
> 
> 
> Any ideas? I can easily reproduce here if any further information is
> required.

A quick bisection with git points to the following commit:


$ git bisect bad
951c6300f74ace35d87c079affc57cfc513a6a35 is the first bad commit
commit 951c6300f74ace35d87c079affc57cfc513a6a35
Author: Richard Henderson <rth@twiddle.net>
Date:   Fri Sep 19 11:39:20 2014 -0700

    tcg: Move some opcode generation functions out of line

    Some of these functions are really quite large.  We have a number of
    things that ought to be circularly dependent, but we duplicated code
    to break that chain for the inlines.

    This saved 25% of the code size of one of the translators I examined.

    Reviewed-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
    Signed-off-by: Richard Henderson <rth@twiddle.net>


ATB,

Mark.

Re: [Qemu-devel] qemu-system-ppc TCG assert with git master

[Bastian Koppelmann]

[-- Attachment #1.1: Type: text/plain, Size: 2393 bytes --]

Hi Mark, sorry I forgot to cc qemu-devel :/

On 03/12/2015 08:41 AM, Mark Cave-Ayland wrote:
> Hi all,
>
> Whilst testing git master in preparation for some OpenBIOS updates, I'm
> seeing the following TCG assert in one of my older test images:
>
>
> $ gdb --args ./qemu-system-ppc -cdrom
> /home/build/src/qemu/image/ppc/ubuntu-5.10-live-powerpc.iso -boot d -g
> 800x600x8
> GNU gdb (GDB) 7.4.1-debian
> Copyright (C) 2012 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later
> <http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law.  Type "show 
> copying"
> and "show warranty" for details.
> This GDB was configured as "x86_64-linux-gnu".
> For bug reporting instructions, please see:
> <http://www.gnu.org/software/gdb/bugs/>...
> Reading symbols from /home/build/rel-qemu-git/bin/qemu-system-ppc...done.
> (gdb) r
> Starting program: /home/build/rel-qemu-git/bin/qemu-system-ppc -cdrom
> /home/build/src/qemu/image/ppc/ubuntu-5.10-live-powerpc.iso -boot d -g
> 800x600x8
> [Thread debugging using libthread_db enabled]
> Using host libthread_db library 
> "/lib/x86_64-linux-gnu/libthread_db.so.1".
> [New Thread 0x7fffe9ef3700 (LWP 11437)]
> [New Thread 0x7fffe5bf1700 (LWP 11438)]
> [New Thread 0x7fffe53f0700 (LWP 11439)]
> [Thread 0x7fffe5bf1700 (LWP 11438) exited]
> [New Thread 0x7fffe5bf1700 (LWP 11443)]
> [Thread 0x7fffe5bf1700 (LWP 11443) exited]
> qemu-system-ppc: /home/build/src/qemu/git/qemu/tcg/optimize.c:212:
> tcg_opt_gen_mov: Assertion `temps[src].state != TCG_TEMP_CONST' failed.

does this fix it?

diff --git a/tcg/tcg-op.h b/tcg/tcg-op.h
index 96adf9a..4c8ff70 100644
--- a/tcg/tcg-op.h
+++ b/tcg/tcg-op.h
@@ -396,7 +396,11 @@ static inline void tcg_gen_and_i32(TCGv_i32 ret, 
TCGv_i32 arg1, TCGv_i32 arg2)

  static inline void tcg_gen_or_i32(TCGv_i32 ret, TCGv_i32 arg1, 
TCGv_i32 arg2)
  {
-    tcg_gen_op3_i32(INDEX_op_or_i32, ret, arg1, arg2);
+    if (TCGV_EQUAL_I32(arg1, arg2)) {
+        tcg_gen_mov_i32(ret, arg1);
+    } else {
+        tcg_gen_op3_i32(INDEX_op_or_i32, ret, arg1, arg2);
+    }
  }

  static inline void tcg_gen_xor_i32(TCGv_i32 ret, TCGv_i32 arg1, 
TCGv_i32 arg2)

The patch is also attached. It is just a revert of tcg_gen_or_i32. I'll 
investigate some more why the optimizer fails here.

Cheers,
Bastian


[-- Attachment #1.2: Type: text/html, Size: 4098 bytes --]

[-- Attachment #2: 0001-tcg-tcg_gen_or_i32-causing-in-some-cases-tcg_opt_gen.patch --]
[-- Type: text/x-patch, Size: 1059 bytes --]

>From 64c6c9e8a312ae6030794ae1c0fb8e45ce0d77a3 Mon Sep 17 00:00:00 2001
From: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Date: Thu, 12 Mar 2015 14:47:29 +0000
Subject: [PATCH] tcg: tcg_gen_or_i32 causing in some cases tcg_opt_gen_mov to
 fail

A first try to fix this is to emit the mov in tcg_or_i32.

Signed-off-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
---
 tcg/tcg-op.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tcg/tcg-op.h b/tcg/tcg-op.h
index 96adf9a..4c8ff70 100644
--- a/tcg/tcg-op.h
+++ b/tcg/tcg-op.h
@@ -396,7 +396,11 @@ static inline void tcg_gen_and_i32(TCGv_i32 ret, TCGv_i32 arg1, TCGv_i32 arg2)
 
 static inline void tcg_gen_or_i32(TCGv_i32 ret, TCGv_i32 arg1, TCGv_i32 arg2)
 {
-    tcg_gen_op3_i32(INDEX_op_or_i32, ret, arg1, arg2);
+    if (TCGV_EQUAL_I32(arg1, arg2)) {
+        tcg_gen_mov_i32(ret, arg1);
+    } else {
+        tcg_gen_op3_i32(INDEX_op_or_i32, ret, arg1, arg2);
+    }
 }
 
 static inline void tcg_gen_xor_i32(TCGv_i32 ret, TCGv_i32 arg1, TCGv_i32 arg2)
-- 
2.3.2

Re: [Qemu-devel] qemu-system-ppc TCG assert with git master

[Mark Cave-Ayland]

On 12/03/15 14:55, Bastian Koppelmann wrote:

Hi Bastian,

> Hi Mark, sorry I forgot to cc qemu-devel :/
> 
> On 03/12/2015 08:41 AM, Mark Cave-Ayland wrote:
>> Hi all,
>>
>> Whilst testing git master in preparation for some OpenBIOS updates, I'm
>> seeing the following TCG assert in one of my older test images:
>>
>>
>> $ gdb --args ./qemu-system-ppc -cdrom
>> /home/build/src/qemu/image/ppc/ubuntu-5.10-live-powerpc.iso -boot d -g
>> 800x600x8
>> GNU gdb (GDB) 7.4.1-debian
>> Copyright (C) 2012 Free Software Foundation, Inc.
>> License GPLv3+: GNU GPL version 3 or later
>> <http://gnu.org/licenses/gpl.html>
>> This is free software: you are free to change and redistribute it.
>> There is NO WARRANTY, to the extent permitted by law.  Type "show
>> copying"
>> and "show warranty" for details.
>> This GDB was configured as "x86_64-linux-gnu".
>> For bug reporting instructions, please see:
>> <http://www.gnu.org/software/gdb/bugs/>...
>> Reading symbols from /home/build/rel-qemu-git/bin/qemu-system-ppc...done.
>> (gdb) r
>> Starting program: /home/build/rel-qemu-git/bin/qemu-system-ppc -cdrom
>> /home/build/src/qemu/image/ppc/ubuntu-5.10-live-powerpc.iso -boot d -g
>> 800x600x8
>> [Thread debugging using libthread_db enabled]
>> Using host libthread_db library
>> "/lib/x86_64-linux-gnu/libthread_db.so.1".
>> [New Thread 0x7fffe9ef3700 (LWP 11437)]
>> [New Thread 0x7fffe5bf1700 (LWP 11438)]
>> [New Thread 0x7fffe53f0700 (LWP 11439)]
>> [Thread 0x7fffe5bf1700 (LWP 11438) exited]
>> [New Thread 0x7fffe5bf1700 (LWP 11443)]
>> [Thread 0x7fffe5bf1700 (LWP 11443) exited]
>> qemu-system-ppc: /home/build/src/qemu/git/qemu/tcg/optimize.c:212:
>> tcg_opt_gen_mov: Assertion `temps[src].state != TCG_TEMP_CONST' failed.
> 
> does this fix it?
> 
> diff --git a/tcg/tcg-op.h b/tcg/tcg-op.h
> index 96adf9a..4c8ff70 100644
> --- a/tcg/tcg-op.h
> +++ b/tcg/tcg-op.h
> @@ -396,7 +396,11 @@ static inline void tcg_gen_and_i32(TCGv_i32 ret,
> TCGv_i32 arg1, TCGv_i32 arg2)
> 
>  static inline void tcg_gen_or_i32(TCGv_i32 ret, TCGv_i32 arg1, TCGv_i32
> arg2)
>  {
> -    tcg_gen_op3_i32(INDEX_op_or_i32, ret, arg1, arg2);
> +    if (TCGV_EQUAL_I32(arg1, arg2)) {
> +        tcg_gen_mov_i32(ret, arg1);
> +    } else {
> +        tcg_gen_op3_i32(INDEX_op_or_i32, ret, arg1, arg2);
> +    }
>  }
> 
>  static inline void tcg_gen_xor_i32(TCGv_i32 ret, TCGv_i32 arg1,
> TCGv_i32 arg2)
> 
> The patch is also attached. It is just a revert of tcg_gen_or_i32. I'll
> investigate some more why the optimizer fails here.

Yes indeed, this fixes the issue in my tests here. But from what you're
saying this is more of a workaround rather than a fix?


ATB,

Mark.

Re: [Qemu-devel] qemu-system-ppc TCG assert with git master

[Richard Henderson]

On 03/12/2015 01:41 AM, Mark Cave-Ayland wrote:
> Whilst testing git master in preparation for some OpenBIOS updates, I'm
> seeing the following TCG assert in one of my older test images:
> 
> 
> $ gdb --args ./qemu-system-ppc -cdrom
> /home/build/src/qemu/image/ppc/ubuntu-5.10-live-powerpc.iso -boot d -g
> 800x600x8

Older, eh?  I can only find 5.04.  ;-)

And, fwiw, that doesn't assert.  I get all the way to

Kernel panic - not syncing: VFS: unable to mount root fs on unknown-block(1,0)

So, I guess I need something different to

http://cdimage.ubuntu.com/ubuntu-mate/daily-live/current/vivid-desktop-powerpc.iso

to reproduce this.



r~

Re: [Qemu-devel] qemu-system-ppc TCG assert with git master

[Bastian Koppelmann]

On 03/12/2015 03:41 PM, Richard Henderson wrote:
> On 03/12/2015 01:41 AM, Mark Cave-Ayland wrote:
>> Whilst testing git master in preparation for some OpenBIOS updates, I'm
>> seeing the following TCG assert in one of my older test images:
>>
>>
>> $ gdb --args ./qemu-system-ppc -cdrom
>> /home/build/src/qemu/image/ppc/ubuntu-5.10-live-powerpc.iso -boot d -g
>> 800x600x8
> Older, eh?  I can only find 5.04.  ;-)
>
> And, fwiw, that doesn't assert.  I get all the way to
>
> Kernel panic - not syncing: VFS: unable to mount root fs on unknown-block(1,0)
>
> So, I guess I need something different to
>
> http://cdimage.ubuntu.com/ubuntu-mate/daily-live/current/vivid-desktop-powerpc.iso
>
> to reproduce this.
>
>
>
> r~
>

Hi Richard,

I can reproduce it fine here with 
http://old-releases.ubuntu.com/releases/5.10/.
As far as I see it, the Instruction at 0xc9105830 generates a mov 0 to 
r30, which is optimized by tcg_opt_gen_mov and r30 is set to 
TCG_TEMP_CONST. When 0xc9105838 or r0, r30, r30 should be optimized r30 
is already in the state TCG_TEMP_CONST and the assert fails.

Cheers,
Bastian

Re: [Qemu-devel] qemu-system-ppc TCG assert with git master

[Mark Cave-Ayland]

On 12/03/15 16:51, Bastian Koppelmann wrote:

Hi Bastian,

> On 03/12/2015 03:41 PM, Richard Henderson wrote:
>> On 03/12/2015 01:41 AM, Mark Cave-Ayland wrote:
>>> Whilst testing git master in preparation for some OpenBIOS updates, I'm
>>> seeing the following TCG assert in one of my older test images:
>>>
>>>
>>> $ gdb --args ./qemu-system-ppc -cdrom
>>> /home/build/src/qemu/image/ppc/ubuntu-5.10-live-powerpc.iso -boot d -g
>>> 800x600x8
>> Older, eh?  I can only find 5.04.  ;-)
>>
>> And, fwiw, that doesn't assert.  I get all the way to
>>
>> Kernel panic - not syncing: VFS: unable to mount root fs on
>> unknown-block(1,0)
>>
>> So, I guess I need something different to
>>
>> http://cdimage.ubuntu.com/ubuntu-mate/daily-live/current/vivid-desktop-powerpc.iso
>>
>>
>> to reproduce this.
>>
>>
>>
>> r~
>>
> 
> Hi Richard,
> 
> I can reproduce it fine here with
> http://old-releases.ubuntu.com/releases/5.10/.
> As far as I see it, the Instruction at 0xc9105830 generates a mov 0 to
> r30, which is optimized by tcg_opt_gen_mov and r30 is set to
> TCG_TEMP_CONST. When 0xc9105838 or r0, r30, r30 should be optimized r30
> is already in the state TCG_TEMP_CONST and the assert fails.

Ah great, you're able to reproduce the same issue locally. Hopefully
this will give you both enough information to figure out what is
happening in the optimiser...


Many thanks,

Mark.

Re: [Qemu-devel] qemu-system-ppc TCG assert with git master

[Richard Henderson]

On 03/12/2015 04:38 PM, Mark Cave-Ayland wrote:
> Ah great, you're able to reproduce the same issue locally. Hopefully
> this will give you both enough information to figure out what is
> happening in the optimiser...

Yep, just sent a simple fix.


r~

Re: [Qemu-devel] qemu-system-ppc TCG assert with git master

[Richard Henderson]

On Mar 12, 2015 4:34 PM, Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> wrote:
> Yes indeed, this fixes the issue in my tests here. But from what you're 
> saying this is more of a workaround rather than a fix? 

Correct.  It simply shows a bug in tcg/optimize.c.  At least we have a workaround if a fix proves difficult before the release.


r~