Re: [PATCH v1 06/11] configure: disable MTTCG for MIPS guests

[Richard Henderson]

On 3/23/20 9:15 AM, Alex Bennée wrote:
> While debugging check-acceptance failures I found an instability in
> the mips64el test case. Briefly the test case:
> 
>   retry.py -n 100 -c -- ./mips64el-softmmu/qemu-system-mips64el \
>     -display none -vga none -serial mon:stdio \
>     -machine malta -kernel ./vmlinux-4.7.0-rc1.I6400 \
>     -cpu I6400 -smp 8 -vga std \
>     -append "printk.time=0 clocksource=GIC console=tty0 console=ttyS0 
> panic=-1" \
>     --no-reboot
> 
> Reports about a 9% failure rate:
> 
>   Results summary:
>   0: 91 times (91.00%), avg time 5.547 (0.45 varience/0.67 deviation)
>   -6: 9 times (9.00%), avg time 3.394 (0.02 varience/0.13 deviation)
>   Ran command 100 times, 91 passes
> 
> When re-run with "--accel tcg,thread=single" the instability goes
> away.
> 
>   Results summary:
>   0: 100 times (100.00%), avg time 17.318 (249.76 varience/15.80 deviation)
>   Ran command 100 times, 100 passes
> 
> Which seems to indicate there is some aspect of the MIPS MTTCG fixes
> that has been missed. Ideally we would fix that but I'm afraid I don't
> have time to investigate and am not super familiar with the
> architecture anyway. In lieu of someone tracking down the failure lets
> disable it for now.
> 
> Signed-off-by: Alex Bennée <address@hidden>
> Acked-by: Philippe Mathieu-Daudé <address@hidden>
> Cc: Aleksandar Markovic <address@hidden>
> Cc: Aurelien Jarno <address@hidden>
> Cc: Aleksandar Rikalo <address@hidden>

Acked-by: Richard Henderson <address@hidden>


r~