x86_64 kernel does not start under qemu

Jan Kiszka jan.kiszka at siemens.com
Fri Mar 8 12:28:17 CET 2019


On 08.03.19 12:19, Richard Weinberger wrote:
> Am Mittwoch, 6. März 2019, 17:39:38 CET schrieb Jan Kiszka:
>> On 06.03.19 16:33, Richard Weinberger wrote:
>>> Am Mittwoch, 6. März 2019, 14:43:55 CET schrieb Jan Kiszka:
>>>> On 06.03.19 14:10, Jan Kiszka wrote:
>>>>> On 06.03.19 12:28, Lange Norbert via Xenomai wrote:
>>>>>> Hello,
>>>>>>
>>>>>> I have a similar issue on real hardware (cc Philippe). Can you try booting
>>>>>> with notscdeadline?
>>>>>>
>>>>>
>>>>> I would be surprised if it's that: QEMU does not emulate this APIC feature, only
>>>>> KVM does.
>>>>>
>>>>> I need to reproduce. Which QEMU version?
>>>>>
>>>>
>>>> Just booted current ipipe-x86-4.14.y (4.14.103) in QEMU 3.1+ (some development
>>>> snapshot) with -smp 4 - works fine. But these are likely quite a few variations
>>>> from your setup.
>>>
>>> I'm on qemu 2.11.2.
>>
>> That one might still be serializing SMP, thus only use one core on the host.
> 
> Well, why is this a problem for Xenomai?
> Does it deadlock if you have more than one cpu and these are not truly parallel?
> This seems a little odd to me.

I the past, this de-parallelization triggered race conditions more easily as it widened the race windows massively. Whatever came out of it remained a Xenomai or I-pipe bug that could theoretically occur on real hardware as well.

> 
>> Currently trying to emulate that as it changes timing.
> 
> Just retried with latest qemu (v3.1.0-2421-g9b748c5e061b), same problem.

Yeah, I suspect the kernel config. Didn't have time to try defconfig so far.

>   
>>> Is this plain ipipe? Just figured that you need to prepare the kernel
>>> with Xenomai to trigger the problem.
>>> Xenomai is 3.0.8.
>>
>> I have Xenomai stable/v3.0.x running as well.
> 
> What kernel config are you using and what is your qemu command line?

Currently used config attached, command line:

qemu-system-x86_64 -drive file=/path/disk.img,discard=unmap,if=none,id=disk -device ide-hd,drive=disk -snapshot -m 1G -serial mon:stdio -s -smp 4 -machine q35,pit=off -fsdev local,path=/path/shared,security_model=none,id=vfs -device virtio-9p-pci,addr=1f.7,mount_tag=host,fsdev=vfs

Jan

-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux
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