Re: [Qemu-devel] [PULL 22/26] target/aarch64: optimize indirect branches

["Alex Bennée" <alex.bennee@linaro.org>]

Richard Henderson <rth@twiddle.net> writes:

> On 06/07/2017 07:11 AM, Alex Bennée wrote:
>>
>> Richard Henderson <rth@twiddle.net> writes:
>>
>>> From: "Emilio G. Cota" <cota@braap.org>
>>>
>>> Measurements:
>>>
>>> [Baseline performance is that before applying this and the previous
>>> commit]
>>
>> Sadly this has regressed my qemu-system-aarch64 EL2 run. It was slightly
>> masked by an unrelated assertion breakage which I had to fix. However
>> with this patch my boot hangs spinning all 4 threads. Once reverted
>> things work again.
>>
>> My command line:
>>
>>    timeout -k 1s --foreground 120s ./aarch64-softmmu/qemu-system-aarch64 -machine type=virt -display none -m 4096 -cpu cortex-a57 -serial mon:stdio -netdev user,id=unet -device virtio-net-device,netdev=unet -drive file=/home/alex/lsrc/qemu/images/jessie-arm64.qcow2,id=myblock,index=0,if=none -device virtio-blk-device,drive=myblock -append "console=ttyAMA0 root=/dev/vda1 systemd.unit=benchmark.service" -kernel /home/alex/lsrc/qemu/images/aarch64-current-linux-kernel-only.img -smp 4 -machine gic-version=3 -machine virtualization=true -name debug-threads=on
>
> If you ignore the timeout, does it complete eventually?

It seems to hang indefinitely. The difference is between no output and
the usual kernel output.

> It may not be the same thing, but that pull left out the final patch
> for target/alpha that enabled goto_ptr.  But as I hadn't seen a
> similar problem with other guests, I was assuming that the problem was
> in hw/alpha/, or some other bit of the interrupt chain.

Given output is being suppressed I wonder if there is some funkyness
with IRQs going on here?

>
>
> r~


--
Alex Bennée