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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 4CD87C43331 for ; Mon, 11 Nov 2019 03:05:42 +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 17A11207FA for ; Mon, 11 Nov 2019 03:05:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="lHIHI7p/" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 17A11207FA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:48720 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iU01N-0006YQ-5y for qemu-devel@archiver.kernel.org; Sun, 10 Nov 2019 22:05:41 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:57826) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iU00N-0005hw-8r for qemu-devel@nongnu.org; Sun, 10 Nov 2019 22:04:40 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iU00M-000770-7S for qemu-devel@nongnu.org; Sun, 10 Nov 2019 22:04:39 -0500 Received: from mail-qt1-x829.google.com ([2607:f8b0:4864:20::829]:42476) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1iU00M-00075Z-1e for qemu-devel@nongnu.org; Sun, 10 Nov 2019 22:04:38 -0500 Received: by mail-qt1-x829.google.com with SMTP id t20so14143773qtn.9 for ; Sun, 10 Nov 2019 19:04:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=s21XsScROhu9BPmbzGcegcYHTdkPFhp5GNL2cd4PxbQ=; b=lHIHI7p/r0giqXhBuGIZTt9zqLjVH/cm3hvX6R3JDUCmIvBCXP4RL/iU0REkYn+lJg VBwHj5196iFxzjLkbOlRgKQXcgu2EnT1sM8txIrRx6rt+5ofNp8ntZm9xXoA0UlKAUmz plhdmv76n5zJLHDJ+LnpkSGmmuBrxhE8jOyww= 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=s21XsScROhu9BPmbzGcegcYHTdkPFhp5GNL2cd4PxbQ=; b=N6AEiRbLO4DikYLHJlwehJZ3T1yvus7i2BfJfe2P+qDOIUUjLMD+KlVmqvf2GjS/f1 kXOs83Arb9saniR2KuAjA8KNRA9fGwT+mKUh05ERf9sCH4E3p5Q+yIuwJb3aGLspRctJ HdU7H9ggyk/zsVfDa1Mv33chhrG7mzw1bfjohM7xNf4BlN+hQi9ONo45wnB8MQHRz8UF eWq5rYGRpiukNu57WqPlJOCRulbE2P4Ks8r4S8+SF58wAbKI3HhWLZ2uqbbyL/BdDh8z jkmd4c7IUdZnh/jQFFu0nFQwHUJ0jX75VNP8nPVXTUFCpFjN1bwzfU1qreK8tiFtutCA ubkw== X-Gm-Message-State: APjAAAU57YaOa1SM+siSFCl/d0z+jlFAXThy5r8JXjx01XhWUKTPS+bz 2DKB1X+F5EFdAKkNmkBauWDj6koRAiX22AnS7dcIWg== X-Google-Smtp-Source: APXvYqzEgRqM2b1k3cEN4mloUeEOhrf8cOZLFKV98ttWSKpDVQ51Q/jYgDxVozA4BQjDVb9G2TwgPcL03Ye994sE63s= X-Received: by 2002:ac8:7216:: with SMTP id a22mr23844828qtp.187.1573441476623; Sun, 10 Nov 2019 19:04:36 -0800 (PST) MIME-Version: 1.0 References: <20191105105456.7xbhtistnbp272lj@sirius.home.kraxel.org> <20191106084344.GB189998@stefanha-x1.localdomain> In-Reply-To: <20191106084344.GB189998@stefanha-x1.localdomain> From: David Stevens Date: Mon, 11 Nov 2019 12:04:25 +0900 Message-ID: Subject: Re: guest / host buffer sharing ... To: Stefan Hajnoczi 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::829 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 , Daniel Vetter , Alexandre Courbot , qemu-devel@nongnu.org, Tomasz Figa , Keiichi Watanabe , Gerd Hoffmann , Hans Verkuil , =?UTF-8?Q?St=C3=A9phane_Marchesin?= , Dylan Reid , Gurchetan Singh , Dmitry Morozov , Pawel Osciak , Linux Media Mailing List Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" > My question would be "what is the actual problem you are trying to > solve?". One problem that needs to be solved is sharing buffers between devices. With the out-of-tree Wayland device, to share virtio-gpu buffers we've been using the virtio resource id. However, that approach isn't necessarily the right approach, especially once there are more devices allocating/sharing buffers. Specifically, this issue came up in the recent RFC about adding a virtio video decoder device. Having a centralized buffer allocator device is one way to deal with sharing buffers, since it gives a definitive buffer identifier that can be used by all drivers/devices to refer to the buffer. That being said, I think the device as proposed is insufficient, as such a centralized buffer allocator should probably be responsible for allocating all shared buffers, not just linear guest ram buffers. -David