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

[Baolu Lu <baolu.lu@linux.intel.com>]

On 6/21/2026 3:22 AM, Oliver Lin wrote:
> On Lenovo ThinkPad P50s, enabling Intel IOMMU causes TPM
> initialization failures, suspend/resume issues, and prevents the
> system from powering off completely.
> 
> The system works correctly with intel_iommu=off. A locally tested
> kernel with this DMI quirk also works correctly without requiring the
> kernel parameter.
> 
> Add a DMI quirk to disable Intel IOMMU on this platform.
> 
> Link:https://bugzilla.kernel.org/show_bug.cgi?id=221674
> Signed-off-by: Oliver Lin<oliver@liuxiaozhen.dev>
> ---
>   drivers/iommu/intel/iommu.c | 19 +++++++++++++++++++
>   1 file changed, 19 insertions(+)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 849d06dfe1ae..a072e9ef63ef 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -278,6 +278,19 @@ static int __init intel_iommu_setup(char *str)
>   
>   	return 1;
>   }
> +
> +static const struct dmi_system_id intel_iommu_broken_dmar_table[] __initconst = {
> +	{
> +		.ident = "Lenovo ThinkPad P50s",
> +		.matches = {
> +			DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
> +			DMI_MATCH(DMI_PRODUCT_NAME, "20FLCTO1WW"),
> +			DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad P50s"),
> +		},
> +	},
> +	{}
> +};

Is this a broken ACPI DMAR table? If so, please try updating to the
latest firmware. Otherwise, report the issue to the laptop vendor and
ask them to resolve it, especially if they claim their product supports
Linux.

Thanks,
baolu