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 0AFD4C83003 for ; Wed, 29 Apr 2020 10:10:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D762A2074A for ; Wed, 29 Apr 2020 10:10:06 +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="ZatmEfpD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726765AbgD2KKG (ORCPT ); Wed, 29 Apr 2020 06:10:06 -0400 Received: from mail27.static.mailgun.info ([104.130.122.27]:37732 "EHLO mail27.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726484AbgD2KKF (ORCPT ); Wed, 29 Apr 2020 06:10:05 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1588155005; h=In-Reply-To: Content-Type: MIME-Version: References: Reply-To: Message-ID: Subject: Cc: To: From: Date: Sender; bh=2mdlW9Q66AJBST1VWjfJfw3PhP2uQD6RM0aPJIOJ2Xg=; b=ZatmEfpD3Bsh8QryubtC4mP7Huo8BjQhW1fMtlsRmY8x8PVeQjmapR1kYrQT/eubPjz0BRK5 gZR7J8jknXaGUwJ/MzYX+kVbXrpKkIlB+U5LOW68xKruDSRReFj66NjT1XK5M0vdFKVNvXQM wliILA6/W+ujkXXp2tNYhZ2VaaU= X-Mailgun-Sending-Ip: 104.130.122.27 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 5ea9527a.7fef5d0e11f0-smtp-out-n04; Wed, 29 Apr 2020 10:10:02 -0000 (UTC) Received: by smtp.codeaurora.org (Postfix, from userid 1001) id ED255C43636; Wed, 29 Apr 2020 10:10:01 +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 D98A0C433CB; Wed, 29 Apr 2020 10:09:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org D98A0C433CB 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 15:39:53 +0530 From: Srivatsa Vaddagiri To: "Michael S. Tsirkin" Cc: Lu Baolu , tsoni@codeaurora.org, virtio-dev@lists.oasis-open.org, konrad.wilk@oracle.com, jan.kiszka@siemens.com, jasowang@redhat.com, christoffer.dall@arm.com, virtualization@lists.linux-foundation.org, alex.bennee@linaro.org, iommu@lists.linux-foundation.org, stefano.stabellini@xilinx.com, will@kernel.org, linux-kernel@vger.kernel.org, pratikp@codeaurora.org Subject: Re: [PATCH 5/5] virtio: Add bounce DMA ops Message-ID: <20200429100953.GE5097@quicinc.com> Reply-To: Srivatsa Vaddagiri References: <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> <275eba4b-dd35-aa95-b2e3-9c5cbf7c6d71@linux.intel.com> <20200429004531-mutt-send-email-mst@kernel.org> <20200429023842-mutt-send-email-mst@kernel.org> <20200429094410.GD5097@quicinc.com> <20200429055125-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20200429055125-mutt-send-email-mst@kernel.org> 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 * Michael S. Tsirkin [2020-04-29 05:52:05]: > > > So it seems that with modern Linux, all one needs > > > to do on x86 is mark the device as untrusted. > > > It's already possible to do this with ACPI and with OF - would that be > > > sufficient for achieving what this patchset is trying to do? > > > > In my case, its not sufficient to just mark virtio device untrusted and thus > > activate the use of swiotlb. All of the secondary VM memory, including those > > allocate by swiotlb driver, is private to it. > > So why not make the bounce buffer memory shared then? Its a limitation by our hypervisor. When a secondary VM is created, two memory segments are allocated - one private and other shared. There is no provision for the secondary VM to make part of its private memory shared after it boots. I can perhaps consider a change in swiotlb driver to accept the second shared memory segment as its main working area (rather than allocate its own). That would still not work I think where swiotlb is used for pass-thr devices (when private memory is fine) as well as virtio devices (when shared memory is required). -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation