RE: [PATCH v3 5/6] iommu: Use EINVAL for incompatible device/domain in ->attach_dev

["Tian, Kevin" <kevin.tian@intel.com>]

> From: Nicolin Chen <nicolinc@nvidia.com>
> Sent: Thursday, September 15, 2022 3:54 PM
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 1f2cd43cf9bc..51ef42b1bd4e 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -4158,19 +4158,15 @@ static int prepare_domain_attach_device(struct
> iommu_domain *domain,
>  		return -ENODEV;
> 
>  	if (dmar_domain->force_snooping && !ecap_sc_support(iommu-
> >ecap))
> -		return -EOPNOTSUPP;
> +		return -EINVAL;
> 
>  	/* check if this iommu agaw is sufficient for max mapped address */
>  	addr_width = agaw_to_width(iommu->agaw);
>  	if (addr_width > cap_mgaw(iommu->cap))
>  		addr_width = cap_mgaw(iommu->cap);
> 
> -	if (dmar_domain->max_addr > (1LL << addr_width)) {
> -		dev_err(dev, "%s: iommu width (%d) is not "
> -		        "sufficient for the mapped address (%llx)\n",
> -		        __func__, addr_width, dmar_domain->max_addr);
> -		return -EFAULT;
> -	}
> +	if (dmar_domain->max_addr > (1LL << addr_width))
> +		return -EINVAL;
>  	dmar_domain->gaw = addr_width;
> 
>  	/*

Above lacks of a conversion in intel-iommu:

intel_iommu_attach_device()
	if (domain->type == IOMMU_DOMAIN_UNMANAGED &&
	    device_is_rmrr_locked(dev)) {
		dev_warn(dev, "Device is ineligible for IOMMU domain attach due to platform RMRR requirement.  Contact your platform vendor.\n");
		return -EPERM;
	}

since it's based on the domain type, picking a different domain
may work in theory though it won't apply to vfio which always
creates unmanaged type.