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

[Jan Beulich <jbeulich@xxxxxxxx>]

On 31.12.2019 08:52,  Aaron Janse  wrote:
> I'd like to note that Ubuntu, unlike Qubes, doesn't need to try
> any `MP-BIOS bug` fallbacks.

"Doesn't need to try" is supposed to mean what? That it gets past
the timer interrupt initialization, meaning if it crashes another
way, it's a different problem? Or instead meaning it works
(contrary to information found elsewhere), suggesting there's a
Qubes side change involved?

> # Things that have been tried
> 
> Disabling APIC entirely (`noapic x2apic=off`)
> - This is avoiding the problem, not fixing it
> - QubeOS requires APIC anyway, so this is not an option for many of us
> 
> Switching the timer to HPET (via the `clocksource` flag)
> - This didn't fix the panic (I've tried `acpi` and `pit`)
> - On my XPS 13, this doesn't change any of the timer error output
> - Ubuntu works on my laptop using HPET
> - 
> http://xenbits.xen.org/docs/unstable/misc/xen-command-line.html#clocksource-x86

Did you try disabling use of the IOMMU ("iommu=0" on the Xen
command line)?

> Updating to 5.4 Linux kernel [77]
> - This didn't fix the panic

As long as you don't even reach Dom0 initialization, no change
whatsoever to the Dom0 kernel will possibly help.

If this is as common a problem as you say, it's hard to believe
this has never worked on any of these systems. Hence it would be
helpful to know starting from which version this has been
regressed.

Jan

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