Re: [BUG] s2idle: unrecoverable sleep on ThinkPad P16s Gen 4 AMD, (Strix Point) when more than 16 logical CPUs are online

[Mario Limonciello <mario.limonciello@amd.com>]

On 9/23/26 11:12, Fourhundred Thecat wrote:
> On 2026-09-23 16:36, Mario Limonciello wrote:
>>
>>
>> Some other thoughts that might be the root cause based on other 
>> historical issues.
>>
>> 1) Have you changed TPM policy or Pluton policy in BIOS setup?  What 
>> did you change it from and to.
>> 2) Have you enabled a storage security password?  If you disable it 
>> does it help this issue?
>> 3) Do you have WWAN in your device?  If you disable it does it help?
>> 4) Does booting with `amd_iommu=off` help?
> 
> 4) amd_iommu=off
> 
> Yes, that fixes it. With amd_iommu=off and all 24 CPUs online, suspend/ 
> resume works reliably.
> 
> So this is not really a CPU count problem. nr_cpus=16 was only masking 
> an IOMMU interaction. But narrowing it further was surprising: neither 
> of the IOMMU's two functions is responsible on its own. All of the 
> following were run with all 24 CPUs online, and I verified in each case 
> that the parameter actually took effect:
> 
>    amd_iommu=off            IOMMU off entirely                     WAKES
>    intremap=off             IR off, DMA remapping on               no wake
>    iommu=pt                 DMA passthrough, IR on                 no wake
>    amd_iommu_intr=legacy    legacy GA mode, IR on, DMA on          no wake
> 
> Verification for each:
> 
>    intremap=off           /proc/interrupts went from 58 IR- lines to 0,
>                           and irq 1 (i8042) is no longer IR-IO-APIC.
>                           iommu still enabled, domain type Translated.
>    iommu=pt               "iommu: Default domain type: Passthrough (set via
>                           kernel command line)", all 40 PCI devices in
>                           identity domains, IR still on (58 IR- lines).
>    amd_iommu_intr=legacy  "AMD-Vi: Virtual APIC enabled" no longer printed,
>                           only "AMD-Vi: Interrupt remapping enabled".
> 
> So only disabling the IOMMU outright helps. Turning off interrupt 
> remapping alone, bypassing DMA translation alone, or dropping out of 
> vAPIC/GA mode all still hang.
> 
> The CPU dependency is still there on top of that. With the IOMMU 
> enabled, nr_cpus=16 works and 24 CPUs hangs. Offlining cpu16-23 by 
> hotplug after booting with all 24 does not help; the CPUs have to never 
> be brought up. cpu16-23 here are the second SMT thread of the eight 
> Zen5c cores (APIC ids 17,19..31).
> 
> Both conditions appear to be required: the IOMMU enabled, and more than 
> 16 CPUs brought up at boot. Either one alone is fine.
> 
> 
> 1) TPM / Pluton policy
> 
> Current values:
> 
>    TpmSelection            = DiscreteTPM2.0   (possible: 
> DiscreteTPM2.0;PlutonTPM2.0)
>    PlutonSecurityProcessor = Disable
>    SecurityChip            = Enable
> 
> The TPM that binds is a discrete STMicro part, tpm0 -> STM0925:00.
> 
> I did change this. As I recall I disabled Microsoft Pluton, which moves 
> the TPM selection off the PlutonTPM2.0 default onto the discrete part, 
> so Enable -> Disable for Pluton and PlutonTPM2.0 -> DiscreteTPM2.0 for 
> the selection. I will confirm the exact original values in setup. I have 
> not yet tested whether restoring the Pluton default changes the 
> behaviour, since the IOMMU result looked more promising.
> 
> 
> 2) Storage security password
> 
> None enrolled. HardDiskPasswordControl=Disable, and the HDD, NVMe, 
> Admin, System and Power-on authentication slots all report is_enabled=0. 
> BlockSIDAuthentication=Enable is the only non-default setting in that 
> area. Nothing to disable, so nothing to test.
> 
> 
> 3) WWAN
> 
> Yes: Quectel [1eac:1007] at 0000:c4:00.0, attached over MHI, exposing 
> wwan0. Its power/wakeup is enabled. Not yet tested with 
> WirelessWANAccess disabled in BIOS.
> 
> 
> so please suggest which test I should do next, now that we have more info

Of your above the most likely cause is PlutonSecurityProcessor = 
Disable.  Please try to re-enable that and then try with IOMMU enabled.