x86_64 kernel does not start under qemu

Philippe Gerum rpm at xenomai.org
Wed Mar 6 15:00:53 CET 2019

On 3/6/19 2:43 PM, Jan Kiszka via Xenomai wrote:
> 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.

Passing notscdeadline works around an issue on 4.14.x with a kernel tick
being lost some time after cobalt grabs the timer hardware, and starts
emulating the host tick. Seen on both qemu and real SoC. Why and how, I
don't know yet. This bug is not easily reproducible. Raising the number
of CPUs in qemu might lower the odds of seeing it.


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