If IOMMU protocol is installed, PciHostBridge just calls IOMMU AllocateBuffer/FreeBuffer/Map/Unmap. PciHostBridge does not set IOMMU access attribute, because it does not know which device request the DMA. This work is done by PciBus driver. Cc: Ruiyu Ni <ruiyu.ni@intel.com> Cc: Leo Duran <leo.duran@amd.com> Cc: Brijesh Singh <brijesh.singh@amd.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Previous patch Tested-by: Brijesh Singh <brijesh.singh@amd.com> Previous patch Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Jiewen Yao <jiewen.yao@intel.com> Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com> Reviewed-by: Leo Duran <leo.duran@amd.com>