Comment 8 for bug 1649718

I think this is related to kvm module in 4.4's in-kernel irq chip.

If one runs with kernel_irqchip=off property set on the qemu command, then
even Xenial on Xenial SMP
never fails.

Installing the 16.04 HWE Edge kernel (4.8.0-30) on my Xenial host resolves
this as well.

On Wed, Dec 14, 2016 at 8:17 PM, Ryan Harper <email address hidden>
wrote:

> The other oddity, running the guest with 1 cpu always works for me in the
> cases where it failed before.
>
>
> On Wed, Dec 14, 2016 at 5:37 PM, Ryan Harper <email address hidden>
> wrote:
>
>>
>>
>> On Wed, Dec 14, 2016 at 4:31 PM, Seth Forshee <
>> <email address hidden>> wrote:
>>
>>> Looking at kernel 4.9, the RTC_UIE_ON ioctl sets an alarm via the
>>> cmos_rtc driver. This does a couple of things.
>>>
>>> 1. Disables the CMOS RTC alarm interrupt, writes an alarm time to the
>>> CMOS RTC, then enables the alarm interrupt.
>>>
>>> 2. When configured to emulate an RTC using the HPET (which our kernel
>>> is), makes sure HPET timer 1 is initialized for RTC emulation.
>>>
>>> Based on this I looked at the diffs for hw/timer/mc146818rtc.c (which
>>> seems to be the CMOS RTC device) and hw/timer/hpet.c between the two
>>> qemu versions. The differences all look pretty trivial, I don't see
>>> anything which looks like it would have fixed the problem.
>>>
>>
>> It's a guest kernel + qemu interaction. In the past, there was an issue
>> w.r.t
>> ensuring RTC interrupts were being delivered; that's what's currently
>> broken.
>>
>> Comparing: grep rtc /proc/interrupts where it works (Trusty) vs failed,
>> and you can see
>> that we get at most a few interrupts to the RTC device.
>>
>> There isn't a whole lot of change to qemu's RTC between 2.5 and 2.6.1 in
>> yakkety
>> So, I need to see if running yakkety qemu on Xenial fixes things as well
>> so we can
>> continue to narrow down where the regression was introduced.
>>
>>
>>>
>>> --
>>> You received this bug notification because you are subscribed to qemu in
>>> Ubuntu.
>>> https://bugs.launchpad.net/bugs/1649718
>>>
>>> Title:
>>> Linux rtc self test fails in a VM under xenial
>>>
>>> To manage notifications about this bug go to:
>>> https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1649718/
>>> +subscriptions
>>>
>>
>>
>