Re: IOMMU faults after S3

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

On Thu, Apr 02, 2026 at 10:47:53AM +0200, Jan Beulich wrote:
> On 02.04.2026 10:39, Jan Beulich wrote:
> > On 02.04.2026 10:08, Marek Marczykowski-Górecki wrote:
> >> The xl dmesg output (from MTL this time):
> >>
> >>     (XEN) [  123.477511] Entering ACPI S3 state.
> >>     (XEN) [18446743903.571842] _disable_pit_irq:2649: using_pit: 0, 
> >> cpu_has_apic: 1
> >>     (XEN) [18446743903.571856] _disable_pit_irq:2659: 
> >> cpuidle_using_deep_cstate: 1, boot_cpu_has(X86_FEATURE_XEN_ARAT): 0
> > 
> > XEN_ARAT being off is the one odd aspect here. That'll want tracking down
> > separately. As per xen-cpuid output (below) ARAT is available.
> 
> For this you may want to also add logging to intel_init_arat(): Since opt_arat
> can be false only due to command line option use, it can only be the function
> not being called (which looks impossible on plain staging code), or 
> cpu_has_arat
> being false despite the xen-cpuid output that you supplied earlier 
> (inexplicable
> as well, at least for now).

Hm, I got this:

    (XEN) [   11.403340] intel_init_arat:674: opt_arat: 1, cpu_has_arat: 0

so, cpu_has_arat=0 ...
next lines are those, to hint when it happened in the boot process:

    (XEN) [   11.409754] mwait-idle: MWAIT substates: 0x11112020
    (XEN) [   11.416130] mwait-idle: v0.4.1 model 0xaa
    (XEN) [   11.422396] mwait-idle: lapic_timer_reliable_states 0x2

Looks like calculate_host_policy() runs much later...


-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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