Re: [Xen-devel] [BUG] panic: "IO-APIC + timer doesn't work" - several people have reproduced

[Jason Andryuk <jandryuk@xxxxxxxxx>]

On Fri, Apr 17, 2020 at 5:31 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>
> On 17.03.2020 16:23, Jason Andryuk wrote:
> > Below is the diff.  It was messier and I tidied it up some.
>
> I've looked into this some more. I can see how what we currently
> do is not in line with firmware handing off with LegacyReplacement
> mode enabled. However, this case doesn't look to apply here:

Thanks for taking a look again.  Sorry for the slow response.  I
wanted to dig through the linux history to see if there was a reason
for enabling the periodic timer there, but I haven't gotten around to
it.

> So right now the only possible approach I see to address your
> problem is to add yet another fallback mode to check_timer(),
> forcing LegacyReplacement mode to be enabled. But between /
> after which step(s) to put this there isn't at all obvious to me.

I don't really have a good suggestion here.

Aaron, I'm curious to know if you've tried this patch on your hardware
and if it helped.

Thanks again,
Jason