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

[Baolu Lu]

On 7/3/26 17:23, Oliver Lin wrote:
> Lenovo ThinkPad P50s exhibits firmware issues when Intel VT-d is enabled.

Why not fix the firmware issue instead?

> With IOMMU enabled, the system reports DMAR DMA faults during boot,
> TPM 2.0 (tpm_crb) fails to initialize with timeout errors, and the
> machine cannot shut down or resume reliably. Booting with
> intel_iommu=off avoids these issues.

So the driver already provides a command-line workaround for this
firmware issue, right? Why is a hardcoded kernel quirk necessary here?

> Add a DMI quirk to disable Intel IOMMU by default on this platform.
> If the user explicitly specifies intel_iommu=on on the kernel command
> line, do not apply the quirk so that VT-d can still be enabled for
> testing and debugging.
>
> Signed-off-by: Oliver Lin <oliver@xxxxxxxxxxxxxxx>
> ---
>   drivers/iommu/intel/iommu.c | 23 +++++++++++++++++++++++
>   1 file changed, 23 insertions(+)

[..snip...]

Thanks,
baolu