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

[Anushree Mathur]

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:

[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