Re: [PATCH kvm-unit-tests 0/3] Add physical timer test

[Christoffer Dall <cdall@linaro.org>]

On Tue, Jul 18, 2017 at 12:17:07PM +0200, Andrew Jones wrote:
> On Thu, Jul 13, 2017 at 09:20:06PM +0200, Christoffer Dall wrote:
> > Add a test for the vtimer. I've tested on
> >  accel=tcg
> >  accel=kvm                     : on seattle, and mustang
> >  accel=kvm,kernel-irqchip=off  : on mustang
> > 
> > I first fix two issues I had running the basic timer test on APM mustang
> > on using TCG.  I wonder why the vtimer tests worked using TCG for Drew,
> > since they didn't work for me, and I don't see how they would have
> > without patch 1.
> 
> That's weird. I just tested again with a latest qemu master pull and it
> still works for me without patch 1. However, as you and Marc discussed,
> it's the right thing to do with regards to the spec.
> 

What is the command line you use to test this?

By looking at the code in QEMU, I see this:

target/arm/helper.c:gt_recalc_timer()

    if (gt->ctl & 1) {
        ...
    } else {
        gt->ctl &= ~4;
        qemu_set_irq(cpu->gt_timer_outputs[timeridx], 0);
        timer_del(cpu->gt_timer[timeridx]);
        trace_arm_gt_recalc_disabled(timeridx);
    }

So bits 1 and 2 (IMASK and ISTATUS, respectively) are cleared.

I instrumented the code and verified this.

Confusing.

> > 
> > Then I introduce a test for the physical timer.  If you run the ptimer
> > test on a kernel before support for the physical timers was added you
> > get a nice error message plus some spamming in your kernel log.
> 
> Thanks for contributing to kvm-unit-tests!
> 

Thanks for maintaining kvm-unit-tests!

It has actually been incredibly useful for developing my timer patches.

-Christoffer