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=-0.4 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 CBA6AC5DF61 for ; Thu, 7 Nov 2019 12:12:04 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 95F6921D79 for ; Thu, 7 Nov 2019 12:12:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="EKVQuk55" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 95F6921D79 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:41446 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iSgdv-0003fC-Ls for qemu-devel@archiver.kernel.org; Thu, 07 Nov 2019 07:12:03 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:55160) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iSgd2-00036x-Op for qemu-devel@nongnu.org; Thu, 07 Nov 2019 07:11:10 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iSgcz-0006zj-IO for qemu-devel@nongnu.org; Thu, 07 Nov 2019 07:11:07 -0500 Received: from mail-qv1-xf43.google.com ([2607:f8b0:4864:20::f43]:36298) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1iSgcz-0006xI-EW for qemu-devel@nongnu.org; Thu, 07 Nov 2019 07:11:05 -0500 Received: by mail-qv1-xf43.google.com with SMTP id f12so679724qvu.3 for ; Thu, 07 Nov 2019 04:11:04 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=BKA8s1JfODN4WpwTCWOwtgTT+YzZkjzLVM4z9feXflo=; b=EKVQuk55NqGEBZhbV8BVxDQYjsoT81dzTmsRxPY6wkvHgR2201EEbrXM/f+4dt4b8x MPP/nzcAMrp6SuDo7mbSGX+LcQXh9/pd9oETm1jFw8TBDLojxjDHClV4PYzZjrVoAfzl csCkA+bh69AXVz2hqudiqDmMhOKR2EP2/zDBezyvS6xwXVvU6VeH4m5JKswsrvrFK8bR HmHUt1XUt7m8iCpGV+8+6/RH8ExPqoITwjlgKh04ScfyEKG2NEHwTyUI4FssxUMUdT+M pM9jt1TEN20IHzkT063k8iwpbZp2J6R173q2JvMGx6Bb28lCQmAMELV9z9q/3QBIxOjF EIdg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=BKA8s1JfODN4WpwTCWOwtgTT+YzZkjzLVM4z9feXflo=; b=dsQtDfGowpktNkC/Zt92JbSzl2sbd3i51R0CxZjgRuOcN3ayUJG6g7zNO75QZPkgJ2 +BIftWeY6JT/MmQTQXWUTJR/wSpVmoaHPz+0MtsWlK6hCR/cULi0T8d3gGkFe1kkot38 afTSqgoB4M8OFsq3ejLrUqQEYapCIh09fFFYaLZ9PTVoRXUc+brYYvGU73jLUlI09ZH6 ucPehKNaA/NkLc1VSxm7QNiD9/AiX9AFDpR476WWSdwhCCaaGZcpeGvOVO4OSLIF0CEb U7lBGzL1ZBu/f31p5TdlUGvGEo8loh9/NyoEyQzjyw8aybS8wfIHIwcdrWKSKUtTj6DN 1OVQ== X-Gm-Message-State: APjAAAWZTdKLIoovzIQ/R3zurHQEPxlAJ6MV4YIX5q+eWTeMYJFa7Q9S 77KlFll+Kp9TdhOjdI0K6Fejz+xFzLTj+TzUBKg= X-Google-Smtp-Source: APXvYqzsPlvpOUDn7EkcGf9rJWzzK0UmVSKgbkHC5ep6B4ucYn8RQygbhppA26x9x2LAw1qeWeDvK70JS85dMoOF3WQ= X-Received: by 2002:a0c:87b5:: with SMTP id 50mr3064636qvj.143.1573128663596; Thu, 07 Nov 2019 04:11:03 -0800 (PST) MIME-Version: 1.0 References: <20191105105456.7xbhtistnbp272lj@sirius.home.kraxel.org> <20191106084344.GB189998@stefanha-x1.localdomain> <20191106095122.jju7eo57scfoat6a@sirius.home.kraxel.org> <20191106125023.uhdhtqisybilxasr@sirius.home.kraxel.org> In-Reply-To: <20191106125023.uhdhtqisybilxasr@sirius.home.kraxel.org> From: Stefan Hajnoczi Date: Thu, 7 Nov 2019 13:10:52 +0100 Message-ID: Subject: Re: guest / host buffer sharing ... To: Gerd Hoffmann Content-Type: text/plain; charset="UTF-8" X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::f43 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: geoff@hostfission.com, virtio-dev@lists.oasis-open.org, Alex Lau , Alexandre Courbot , qemu-devel , Tomasz Figa , Keiichi Watanabe , David Stevens , Daniel Vetter , =?UTF-8?Q?St=C3=A9phane_Marchesin?= , Dylan Reid , Gurchetan Singh , Hans Verkuil , Dmitry Morozov , Pawel Osciak , Linux Media Mailing List Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Nov 6, 2019 at 1:50 PM Gerd Hoffmann wrote: > > In the graphics buffer sharing use case, how does the other side > > determine how to interpret this data? > > The idea is to have free form properties (name=value, with value being > a string) for that kind of metadata. > > > Shouldn't there be a VIRTIO > > device spec for the messaging so compatible implementations can be > > written by others? > > Adding a list of common properties to the spec certainly makes sense, > so everybody uses the same names. Adding struct-ed properties for > common use cases might be useful too. Why not define VIRTIO devices for wayland and friends? This new device exposes buffer sharing plus properties - effectively a new device model nested inside VIRTIO. The VIRTIO device model has the necessary primitives to solve the buffer sharing problem so I'm struggling to see the purpose of this new device. Custom/niche applications that do not wish to standardize their device type can maintain out-of-tree VIRTIO devices. Both kernel and userspace drivers can be written for the device and there is already VIRTIO driver code that can be reused. They have access to the full VIRTIO device model, including feature negotiation and configuration space. Stefan