Comment 7 for bug 1649718

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
>>
>
>