Re: qemu-system-ppc64 option -smp 2 broken with commit 20b6643324a79860dcdfe811ffe4a79942bca21e

[Anushree Mathur <anushree.mathur@linux.vnet.ibm.com>]

On 6/23/23 19:16, Cédric Le Goater wrote:
> Hello Anushree,
>
> On 6/23/23 13:09, Anushree Mathur wrote:
>> Hi everyone,
>>
>> I was trying to boot rhel9.3 image with upstream qemu-system-ppc64 
>> -smp 2 option and observed a segfault (qemu crash).
>>
>> qemu command line used:
>>
>> qemu-system-ppc64 -name Rhel9.3.ppc64le -smp 2 -m 16G -vga none 
>> -nographic -machine pseries -cpu POWER10 -accel tcg -device 
>> virtio-scsi-pci -drive 
>> file=/home/rh93.qcow2,if=none,format=qcow2,id=hd0 -device 
>> scsi-hd,drive=hd0 -boot c
>>
>> After doing a git bisect, I found the first bad commit which 
>> introduced this issue is below:
>
> Could you please open a gitlab issue on QEMU project ?
>
>  https://gitlab.com/qemu-project/qemu/-/issues
>
> Thanks,
>
> C.
>
>> [qemu]# git bisect good
>> 20b6643324a79860dcdfe811ffe4a79942bca21e is the first bad commit
>> commit 20b6643324a79860dcdfe811ffe4a79942bca21e
>> Author: Richard Henderson <richard.henderson@linaro.org>
>> Date:   Mon Dec 5 17:45:02 2022 -0600
>>
>>      tcg/ppc: Reorg goto_tb implementation
>>
>>      The old ppc64 implementation replaces 2 or 4 insns, which leaves 
>> a race
>>      condition in which a thread could be stopped at a PC in the 
>> middle of
>>      the sequence, and when restarted does not see the complete address
>>      computation and branches to nowhere.
>>
>>      The new implemetation replaces only one insn, swapping between
>>
>>              b       <dest>
>>      and
>>              mtctr   r31
>>
>>      falling through to a general-case indirect branch.
>>
>>      Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
>>      Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>>
>>   tcg/ppc/tcg-target.c.inc | 152 
>> +++++++++++++----------------------------------
>>   tcg/ppc/tcg-target.h     |   3 +-
>>   2 files changed, 41 insertions(+), 114 deletions(-)
>> [qemu]#
>>
>> Can someone please take a look and suggest a fix to resolve this issue?
>>
>> Thanks in advance.
>> Regards,
>> Anushree-Mathur
>>
>>
Hello Cedric,
> As per your mail, I have created the gitlab issue 
> https://gitlab.com/qemu-project/qemu/-/issues/1726.

Thanks & Regards,

Anushree-Mathur

>