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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 87A7EC83003 for ; Wed, 29 Apr 2020 04:09:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5781920731 for ; Wed, 29 Apr 2020 04:09:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="GmElLMCX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726681AbgD2EJm (ORCPT ); Wed, 29 Apr 2020 00:09:42 -0400 Received: from mail26.static.mailgun.info ([104.130.122.26]:17644 "EHLO mail26.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725497AbgD2EJm (ORCPT ); Wed, 29 Apr 2020 00:09:42 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1588133381; h=In-Reply-To: Content-Type: MIME-Version: References: Reply-To: Message-ID: Subject: Cc: To: From: Date: Sender; bh=ZygyuDR/+QYBGGocHbLP5ReISc55KGqtsbV+9Eyjzc4=; b=GmElLMCXAefxRkR0FqYR/fjHxFWbTExS64AKUOtvocZXfrkZ1o4ACkSi7pUXpFyQI1Smk3+f xo4iSIfxwVflZuI+XeV3X6Pr6yOkGaS2/D9uvwL8do7kGztjgN9X45L3w2KqedJ19z76kNTG paimqlPu5UeIcFUKCjQm2nHCj3M= X-Mailgun-Sending-Ip: 104.130.122.26 X-Mailgun-Sid: WyI0MWYwYSIsICJsaW51eC1rZXJuZWxAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by mxa.mailgun.org with ESMTP id 5ea8fe03.7f04b35b69d0-smtp-out-n04; Wed, 29 Apr 2020 04:09:39 -0000 (UTC) Received: by smtp.codeaurora.org (Postfix, from userid 1001) id EC051C433F2; Wed, 29 Apr 2020 04:09:37 +0000 (UTC) Received: from quicinc.com (blr-bdr-fw-01_GlobalNAT_AllZones-Outside.qualcomm.com [103.229.18.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: svaddagi) by smtp.codeaurora.org (Postfix) with ESMTPSA id 5AB9AC433CB; Wed, 29 Apr 2020 04:09:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 5AB9AC433CB Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=none smtp.mailfrom=vatsa@codeaurora.org Date: Wed, 29 Apr 2020 09:39:29 +0530 From: Srivatsa Vaddagiri To: Stefano Stabellini Cc: "Michael S. Tsirkin" , konrad.wilk@oracle.com, jasowang@redhat.com, jan.kiszka@siemens.com, will@kernel.org, stefano.stabellini@xilinx.com, iommu@lists.linux-foundation.org, virtualization@lists.linux-foundation.org, virtio-dev@lists.oasis-open.org, tsoni@codeaurora.org, pratikp@codeaurora.org, christoffer.dall@arm.com, alex.bennee@linaro.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 5/5] virtio: Add bounce DMA ops Message-ID: <20200429040929.GC5097@quicinc.com> Reply-To: Srivatsa Vaddagiri References: <1588073958-1793-1-git-send-email-vatsa@codeaurora.org> <1588073958-1793-6-git-send-email-vatsa@codeaurora.org> <20200428121232-mutt-send-email-mst@kernel.org> <20200428174952.GA5097@quicinc.com> <20200428163448-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Stefano Stabellini [2020-04-28 16:04:34]: > > > Is swiotlb commonly used for multiple devices that may be on different trust > > > boundaries (and not behind a hardware iommu)? > > The trust boundary is not a good way of describing the scenario and I > think it leads to miscommunication. > > A better way to describe the scenario would be that the device can only > DMA to/from a small reserved-memory region advertised on device tree. > > Do we have other instances of devices that can only DMA to/from very > specific and non-configurable address ranges? If so, this series could > follow their example. AFAICT there is no such notion in current DMA API. static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size, bool is_ram) { return end <= min_not_zero(*dev->dma_mask, dev->bus_dma_limit); } Only the max address a device can access is defined and not a range that we seem to need here. I think we need to set the bus_dma_limit to 0 for virtio devices which will force the use of swiotlb_map API. We should also have a per-device swiotlb pool defined, so that swiotlb can use the pool meant for the given device. -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation