Re: [PATCH 2/2] thunderbolt: Use pre-boot DMA protection on AMD systems

[Christoph Hellwig]

On Tue, Mar 15, 2022 at 11:24:55AM -0500, Mario Limonciello wrote:
> -	 * handled natively using IOMMU. It is enabled when IOMMU is
> -	 * enabled and ACPI DMAR table has DMAR_PLATFORM_OPT_IN set.
> +	 * handled natively using IOMMU. It is enabled when the IOMMU is
> +	 * enabled and either:
> +	 * ACPI DMAR table has DMAR_PLATFORM_OPT_IN set
> +	 * or
> +	 * ACPI IVRS table has DMA_REMAP bitset
>  	 */
>  	return sprintf(buf, "%d\n",
> -		       iommu_present(&pci_bus_type) && dmar_platform_optin());
> +		       iommu_present(&pci_bus_type) &&
> +		       (dmar_platform_optin() || amd_ivrs_remap_support()));

Yikes.  No, the thunderbot code does not have any business poking into
either dmar_platform_optin or amd_ivrs_remap_support.  This needs
a proper abstration from the IOMMU code.