On Wed, Dec 14, 2016 at 4:31 PM, Seth Forshee <seth.forshee...@canonical.com
> 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.


>
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> 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:
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https://bugs.launchpad.net/bugs/1649718

Title:
  Linux rtc self test fails in a VM under xenial

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