From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=6YJq=VW=vger.kernel.org=linux-kernel-owner@kernel.org>
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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no
	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 77C12C7618B
	for <linux-kernel@archiver.kernel.org>; Thu, 25 Jul 2019 05:44:20 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [209.132.180.67])
	by mail.kernel.org (Postfix) with ESMTP id 5B79721880
	for <linux-kernel@archiver.kernel.org>; Thu, 25 Jul 2019 05:44:20 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S2391232AbfGYFoT (ORCPT
        <rfc822;linux-kernel@archiver.kernel.org>);
        Thu, 25 Jul 2019 01:44:19 -0400
Received: from verein.lst.de ([213.95.11.211]:58183 "EHLO verein.lst.de"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S2391212AbfGYFoQ (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 25 Jul 2019 01:44:16 -0400
Received: by verein.lst.de (Postfix, from userid 2407)
        id 659C368B20; Thu, 25 Jul 2019 07:44:13 +0200 (CEST)
Date:   Thu, 25 Jul 2019 07:44:13 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Lu Baolu <baolu.lu@linux.intel.com>
Cc:     David Woodhouse <dwmw2@infradead.org>,
        Joerg Roedel <joro@8bytes.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Christoph Hellwig <hch@lst.de>, ashok.raj@intel.com,
        jacob.jun.pan@intel.com, alan.cox@intel.com, kevin.tian@intel.com,
        mika.westerberg@linux.intel.com, Ingo Molnar <mingo@redhat.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        pengfei.xu@intel.com,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Juergen Gross <jgross@suse.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        Jacob Pan <jacob.jun.pan@linux.intel.com>
Subject: Re: [PATCH v5 02/10] iommu/vt-d: Use per-device dma_ops
Message-ID: <20190725054413.GC24527@lst.de>
References: <20190725031717.32317-1-baolu.lu@linux.intel.com> <20190725031717.32317-3-baolu.lu@linux.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20190725031717.32317-3-baolu.lu@linux.intel.com>
User-Agent: Mutt/1.5.17 (2007-11-01)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

>  /* Check if the dev needs to go through non-identity map and unmap process.*/
>  static bool iommu_need_mapping(struct device *dev)
>  {
> -	int ret;
> -
>  	if (iommu_dummy(dev))
>  		return false;
>  
> -	ret = identity_mapping(dev);
> -	if (ret) {
> -		u64 dma_mask = *dev->dma_mask;
> -
> -		if (dev->coherent_dma_mask && dev->coherent_dma_mask < dma_mask)
> -			dma_mask = dev->coherent_dma_mask;
> -
> -		if (dma_mask >= dma_get_required_mask(dev))
> -			return false;

Don't we need to keep this bit so that we still allow the IOMMU
to act if the device has a too small DMA mask to address all memory in
the system, even if if it should otherwise be identity mapped?