Re: [PATCH v3] iommu/vt-d: Disable IOMMU by default on Lenovo ThinkPad P50s

[Oliver Lin]

On 13/7/2026 09:55, Baolu Lu wrote:
 >Why not fix the firmware issue instead?

 >So the driver already provides a command-line workaround for this

 > firmware issue, right? Why is a hardcoded kernel quirk necessary here?


Thanks for the review.

The machine is already running the latest available Lenovo BIOS, version 
1.45. I am not aware of any newer firmware update that fixes the issue, 
and the ThinkPad P50s is no longer receiving firmware updates from Lenovo.

Yes, intel_iommu=off provides a working command-line workaround. With 
VT-d enabled, however, the issue occurs during a normal default boot and 
causes several unrelated failures: DMAR faults are reported, tpm_crb 
times out during initialization, and shutdown and suspend/resume are 
unreliable. Adding intel_iommu=off consistently avoids all of these 
failures.

My reason for proposing a DMI quirk was that users installing a current 
kernel on this platform would otherwise encounter a partially unusable 
system without knowing that the failures are caused by VT-d or that 
intel_iommu=off is required.

That said, I understand the concern about disabling IOMMU functionality 
based on a single platform report. At the moment, my testing is limited 
to one ThinkPad P50s. I can provide the full DMAR, TPM, shutdown, and 
resume logs for both configurations, and I can also look for reports or 
testing from additional P50s systems before pursuing the quirk further.

Would additional reproductions from other P50s machines be required 
before a DMI quirk could be considered, or would you prefer that this 
remain a documented command-line workaround?

Thanks,
Oliver