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=-2.3 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 9828CC3F2C6 for ; Tue, 3 Mar 2020 15:53:29 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 595032073D for ; Tue, 3 Mar 2020 15:53:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 595032073D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=8bytes.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id 34D78863BE; Tue, 3 Mar 2020 15:53:29 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id VI5+yYqpZB7B; Tue, 3 Mar 2020 15:53:28 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by whitealder.osuosl.org (Postfix) with ESMTP id 86F11860E1; Tue, 3 Mar 2020 15:53:28 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 73987C1D89; Tue, 3 Mar 2020 15:53:28 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 533D7C013E; Tue, 3 Mar 2020 15:53:27 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id 3F7E884237; Tue, 3 Mar 2020 15:53:27 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Z3iRiy0w3-54; Tue, 3 Mar 2020 15:53:25 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from theia.8bytes.org (8bytes.org [81.169.241.247]) by whitealder.osuosl.org (Postfix) with ESMTPS id 6563E84B8F; Tue, 3 Mar 2020 15:53:25 +0000 (UTC) Received: by theia.8bytes.org (Postfix, from userid 1000) id 8ADE9668; Tue, 3 Mar 2020 16:53:22 +0100 (CET) Date: Tue, 3 Mar 2020 16:53:19 +0100 From: Joerg Roedel To: "Michael S. Tsirkin" Subject: Re: [PATCH v2 1/3] iommu/virtio: Add topology description to virtio-iommu config space Message-ID: <20200303155318.GA3954@8bytes.org> References: <20200228172537.377327-1-jean-philippe@linaro.org> <20200228172537.377327-2-jean-philippe@linaro.org> <20200302161611.GD7829@8bytes.org> <9004f814-2f7c-9024-3465-6f9661b97b7a@redhat.com> <20200303130155.GA13185@8bytes.org> <20200303084753-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200303084753-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) Cc: Jean-Philippe Brucker , kevin.tian@intel.com, linux-pci@vger.kernel.org, jasowang@redhat.com, virtualization@lists.linux-foundation.org, iommu@lists.linux-foundation.org, sebastien.boeuf@intel.com, jacob.jun.pan@intel.com, bhelgaas@google.com, robin.murphy@arm.com X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Tue, Mar 03, 2020 at 09:00:05AM -0500, Michael S. Tsirkin wrote: > Not necessarily. E.g. some power systems have neither. > There are also systems looking to bypass ACPI e.g. for boot speed. If there is no firmware layer between the hardware and the OS the necessary information the OS needs to run on the hardware is probably hard-coded into the kernel? In that case the same can be done with virtio-iommu tolopology. > That sentence doesn't really answer the question, does it? To be more elaborate, putting this information into config space is a layering violation. Hardware is never completly self-descriptive and that is why there is the firmware which provides the information about the hardware to the OS in a generic way. > Frankly with platform specific interfaces like ACPI, virtio-iommu is > much less compelling. Describing topology as part of the device in a > way that is first, portable, and second, is a good fit for hypervisors, > is to me one of the main reasons virtio-iommu makes sense at all. Virtio-IOMMU makes sense in the first place because it is much faster than emulating one of the hardware IOMMUs. And an ACPI table is also portable to all ACPI platforms, same with device-tree. Regards, Joerg _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu