Re: IOMMU faults after S3

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Thu, Apr 02, 2026 at 04:53:31PM +0200, Jan Beulich wrote:
> On 02.04.2026 16:47, Marek Marczykowski-Górecki wrote:
> > On Thu, Apr 02, 2026 at 12:48:14PM +0200, Jan Beulich wrote:
> >> On 02.04.2026 11:35, Marek Marczykowski-Górecki wrote:
> >>> On Thu, Apr 02, 2026 at 10:39:41AM +0200, 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
> >>>
> >>>> Hmm, but what you didn't log is whether __hpet_setup_msi_irq() actually
> >>>> succeeded everywhere. (And if it did, also logging HPET_Tn_ROUTE() values
> >>>> might be a good idea, if only to double check.)
> >>>
> >>> Updated output:
> >>>
> >>>     (XEN) [18446743899.720395] _disable_pit_irq:2649: using_pit: 0, cpu_has_apic: 1
> >>>     (XEN) [18446743899.720409] _disable_pit_irq:2659: cpuidle_using_deep_cstate: 1, boot_cpu_has(X86_FEATURE_XEN_ARAT): 0
> >>>     (XEN) [18446743899.720420] _disable_pit_irq:2662: init: 0
> >>>     (XEN) [18446743899.720431] hpet_broadcast_resume:663: hpet_events: ffff83046bc1f080
> >>>     (XEN) [18446743899.720579] hpet_broadcast_resume:674: num_hpets_used: 8
> >>>     (XEN) [18446743899.720587] hpet_broadcast_resume:692: cfg: 0x1
> >>>     (XEN) [18446743899.720599] hpet_broadcast_resume:697: i:0, hpet_events[i].msi.irq: 122, hpet_events[i].flags: 0
> >>>     (XEN) [18446743899.720612] hpet_msi_write:283: iommu_intremap: 2 (iommu_intremap_off: 0), HPET_Tn_ROUTE(ch->idx): 0x110
> >>>     (XEN) [18446743899.720638] hpet_msi_write:287: iommu_update_ire_from_msi rc: 0
> >>
> >> So it succeeds, and the low half of HPET_Tn_ROUTE also looks plausible. The high
> >> half is, however, the address that the low half value is written to. It's hard
> >> to imagine that it would be zero when the low half isn't, but it is about the
> >> last thing I can think of which could explain observed behavior. (Yet then, all
> >> of this is pretty meaningless; see below.)
> >>
> >>> And the current debug diff attached.
> >>
> >> Hmm, you log HPET_Tn_ROUTE _before_ our update. That's not very useful. You want
> >> to move that part of logging to the bottom of hpet_msi_write(), or maybe to
> >> where you also log the per-channel cfg value in hpet_broadcast_resume() (thus
> >> making the logging overall less verbose).
> > 
> > This test is with the updated patch (attached) + your extra
> > calculate_host_policy() call and "no-arat" on cmdline:
> 
> And IOMMU faults still occurring as before, I expect.
> 
> Sadly you now log the low halves of HPET_Tn_ROUTE twice, while you don't log
> the high halves at all.

I was missing hpet_read32 there...

Updated:
(XEN) [  116.921573] Entering ACPI S3 state.
(XEN) [18446743895.088893] _disable_pit_irq:2649: using_pit: 0, cpu_has_apic: 1
(XEN) [18446743895.088907] _disable_pit_irq:2659: cpuidle_using_deep_cstate: 1, boot_cpu_has(X86_FEATURE_XEN_ARAT): 0
(XEN) [18446743895.088918] _disable_pit_irq:2662: init: 0
(XEN) [18446743895.088928] hpet_broadcast_resume:662: hpet_events: ffff83046bc1f080
(XEN) [18446743895.089072] hpet_broadcast_resume:673: num_hpets_used: 8
(XEN) [18446743895.089081] hpet_broadcast_resume:691: cfg: 0x1
(XEN) [18446743895.089092] hpet_broadcast_resume:696: i:0, hpet_events[i].msi.irq: 122, hpet_events[i].flags: 0
(XEN) [18446743895.089122] hpet_msi_write:286: iommu_update_ire_from_msi rc: 0
(XEN) [18446743895.089132] hpet_broadcast_resume:700: i:0, __hpet_setup_msi_irq ret: 0
(XEN) [18446743895.089168] hpet_broadcast_resume:710: i:0, cfg: 0xc134, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx)): 0, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx) + 4): 0xf18
(XEN) [18446743895.089180] hpet_broadcast_resume:696: i:1, hpet_events[i].msi.irq: 123, hpet_events[i].flags: 0
(XEN) [18446743895.089203] hpet_msi_write:286: iommu_update_ire_from_msi rc: 0
(XEN) [18446743895.089213] hpet_broadcast_resume:700: i:1, __hpet_setup_msi_irq ret: 0
(XEN) [18446743895.089242] hpet_broadcast_resume:710: i:1, cfg: 0xc104, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx)): 0, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx) + 4): 0xf38
(XEN) [18446743895.089254] hpet_broadcast_resume:696: i:2, hpet_events[i].msi.irq: 124, hpet_events[i].flags: 0
(XEN) [18446743895.089278] hpet_msi_write:286: iommu_update_ire_from_msi rc: 0
(XEN) [18446743895.089288] hpet_broadcast_resume:700: i:2, __hpet_setup_msi_irq ret: 0
(XEN) [18446743895.089316] hpet_broadcast_resume:710: i:2, cfg: 0xc104, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx)): 0, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx) + 4): 0xf58
(XEN) [18446743895.089327] hpet_broadcast_resume:696: i:3, hpet_events[i].msi.irq: 125, hpet_events[i].flags: 0
(XEN) [18446743895.089350] hpet_msi_write:286: iommu_update_ire_from_msi rc: 0
(XEN) [18446743895.089361] hpet_broadcast_resume:700: i:3, __hpet_setup_msi_irq ret: 0
(XEN) [18446743895.089390] hpet_broadcast_resume:710: i:3, cfg: 0xc104, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx)): 0, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx) + 4): 0xf78
(XEN) [18446743895.089401] hpet_broadcast_resume:696: i:4, hpet_events[i].msi.irq: 126, hpet_events[i].flags: 0
(XEN) [18446743895.089425] hpet_msi_write:286: iommu_update_ire_from_msi rc: 0
(XEN) [18446743895.089436] hpet_broadcast_resume:700: i:4, __hpet_setup_msi_irq ret: 0
(XEN) [18446743895.089465] hpet_broadcast_resume:710: i:4, cfg: 0xc104, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx)): 0, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx) + 4): 0xf98
(XEN) [18446743895.089476] hpet_broadcast_resume:696: i:5, hpet_events[i].msi.irq: 127, hpet_events[i].flags: 0
(XEN) [18446743895.089499] hpet_msi_write:286: iommu_update_ire_from_msi rc: 0
(XEN) [18446743895.089509] hpet_broadcast_resume:700: i:5, __hpet_setup_msi_irq ret: 0
(XEN) [18446743895.089540] hpet_broadcast_resume:710: i:5, cfg: 0xc104, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx)): 0, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx) + 4): 0xfb8
(XEN) [18446743895.089551] hpet_broadcast_resume:696: i:6, hpet_events[i].msi.irq: 128, hpet_events[i].flags: 0
(XEN) [18446743895.089574] hpet_msi_write:286: iommu_update_ire_from_msi rc: 0
(XEN) [18446743895.089584] hpet_broadcast_resume:700: i:6, __hpet_setup_msi_irq ret: 0
(XEN) [18446743895.089622] hpet_broadcast_resume:710: i:6, cfg: 0xc104, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx)): 0, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx) + 4): 0xfd8
(XEN) [18446743895.089633] hpet_broadcast_resume:696: i:7, hpet_events[i].msi.irq: 129, hpet_events[i].flags: 0
(XEN) [18446743895.089655] hpet_msi_write:286: iommu_update_ire_from_msi rc: 0
(XEN) [18446743895.089665] hpet_broadcast_resume:700: i:7, __hpet_setup_msi_irq ret: 0
(XEN) [18446743895.089702] hpet_broadcast_resume:710: i:7, cfg: 0xc104, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx)): 0, hpet_read32(HPET_Tn_ROUTE(hpet_events[i].idx) + 4): 0xff8




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

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