Re: [PATCH 09/15] PCI, device core: Move "untrusted" concept to DEVICE_TRUST_ADVERSARY

[Jason Gunthorpe <jgg@ziepe.ca>]

On Sun, Jul 05, 2026 at 03:08:13PM -0700, Dan Williams wrote:

> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> index a08523d348d8..a4233bdf9804 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -291,6 +291,14 @@ config DEVICE_TRUST_NONE
>  	  possible, the device is blocked by an IOMMU from accessing
>  	  assets.
>  
> +config DEVICE_TRUST_ADVERSARY
> +	bool "Adversary"
> +	help
> +	  Device is allowed to bind. Bus, IOMMU, and driver layers may
> +	  react to this trust level by disabling access validation
> +	  bypass mechanisms like PCI ATS. When device is unbound from a
> +	  driver the device is blocked by an IOMMU where possible.
> +
>  config DEVICE_TRUST_AUTO
>  	bool "Auto"
>  	help
> @@ -317,6 +325,11 @@ config BUILTIN_DEVICE_TRUST_AUTO
>  	  a driver and deploy all available mechanisms to allow performant
>  	  direct memory access This trust level does not grant TCB privileges.
>  
> +config BUILTIN_DEVICE_TRUST_ADVERSARY
> +	bool "Adversary"
> +	help
> +	  Deploy mitigations in the IOMMU layer and driver to limit access.

I'm not sure it makes sense to have these options as compile time
defaults. Arguably the non-built in path should only be auto or none
and everything else should be handled by the initrd at runtime. If
necessary a sysfs for the initrd to set a kernel default might make
sense, IDK.

Ideally built in devices should not be any kind that is hooked up to
the iommu.

> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 9abaec0703ef..957ef77911a9 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -588,16 +588,11 @@ static int iova_reserve_iommu_regions(struct device *dev,
>  	return ret;
>  }
>  
> -static bool dev_is_untrusted(struct device *dev)
> -{
> -	return dev_is_pci(dev) && to_pci_dev(dev)->untrusted;
> -}
> -
>  static bool dev_use_swiotlb(struct device *dev, size_t size,
>  			    enum dma_data_direction dir)
>  {
>  	return IS_ENABLED(CONFIG_SWIOTLB) &&
> -		(dev_is_untrusted(dev) ||
> +		(device_untrusted(dev) ||
>  		 dma_kmalloc_needs_bounce(dev, size, dir));
>  }

I think it would be nice to use the new 'adversarial' word here and in
other places instead of untrusted.

Jason