From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CDE7EC282DC for ; Mon, 3 Jun 2019 00:42:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A9DED27A43 for ; Mon, 3 Jun 2019 00:42:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726716AbfFCAmj (ORCPT ); Sun, 2 Jun 2019 20:42:39 -0400 Received: from mga03.intel.com ([134.134.136.65]:65403 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726270AbfFCAmj (ORCPT ); Sun, 2 Jun 2019 20:42:39 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 02 Jun 2019 17:42:39 -0700 X-ExtLoop1: 1 Received: from allen-box.sh.intel.com (HELO [10.239.159.136]) ([10.239.159.136]) by orsmga004.jf.intel.com with ESMTP; 02 Jun 2019 17:42:35 -0700 Cc: baolu.lu@linux.intel.com, David Woodhouse , Joerg Roedel , kevin.tian@intel.com, ashok.raj@intel.com, dima@arista.com, tmurphy@arista.com, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, jacob.jun.pan@intel.com Subject: Re: [PATCH v4 10/15] iommu/vt-d: Probe DMA-capable ACPI name space devices To: Christoph Hellwig References: <20190525054136.27810-1-baolu.lu@linux.intel.com> <20190525054136.27810-11-baolu.lu@linux.intel.com> <20190529061626.GA26055@infradead.org> From: Lu Baolu Message-ID: <23d9d04c-c3fd-716e-dd66-eb5119aad4f9@linux.intel.com> Date: Mon, 3 Jun 2019 08:35:39 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190529061626.GA26055@infradead.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 5/29/19 2:16 PM, Christoph Hellwig wrote: > On Sat, May 25, 2019 at 01:41:31PM +0800, Lu Baolu wrote: >> Some platforms may support ACPI name-space enumerated devices >> that are capable of generating DMA requests. Platforms which >> support DMA remapping explicitly declares any such DMA-capable >> ACPI name-space devices in the platform through ACPI Name-space >> Device Declaration (ANDD) structure and enumerate them through >> the Device Scope of the appropriate remapping hardware unit. >> >> Signed-off-by: Lu Baolu > > Isn't this something that should be handled through the IOMMU API so > that it covers other IOMMU types as well? > > How does this scheme compare to the one implemented in > drivers/acpi/arm64/iort.c? > This part of code was added to be compatible with the past. Yes. I've ever thought about this. But these devices sit on the acpi bus together with other devices which are not DMA-capable. And on some platforms these devices exist on the pci bus as well. Best regards, Baolu