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 2A951C43603 for ; Tue, 17 Dec 2019 13:00:30 +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 DEF31206B7 for ; Tue, 17 Dec 2019 13:00:29 +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="YMCJELu6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DEF31206B7 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]:40160 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ihCSj-0007TB-2h for qemu-devel@archiver.kernel.org; Tue, 17 Dec 2019 08:00:29 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:56033) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ihCRy-0006zh-Me for qemu-devel@nongnu.org; Tue, 17 Dec 2019 07:59:43 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ihCRx-0008ST-NQ for qemu-devel@nongnu.org; Tue, 17 Dec 2019 07:59:42 -0500 Received: from mail-qk1-x742.google.com ([2607:f8b0:4864:20::742]:47008) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1ihCRx-0008RO-Hw for qemu-devel@nongnu.org; Tue, 17 Dec 2019 07:59:41 -0500 Received: by mail-qk1-x742.google.com with SMTP id r14so7700408qke.13 for ; Tue, 17 Dec 2019 04:59:41 -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=4bZpGkKAkvfd+jX4DG0vMQ2qfrG6ll9qDalxUKn1b3E=; b=YMCJELu631QRNTqwkjAcCOyFtrMLDTS5TMyx6OvxxAkDtKxhgfrna//TtU2raSRNzY gwQWOfT1HpZvRZBEsApA0YfgTjyjxYUXxUx9xKZoFDLhlO3noHCZIPQyYpJgt+zfy9qr aPs71Gjd0r2qzgILwvNDn4unYX33ibUDXggyU= 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=4bZpGkKAkvfd+jX4DG0vMQ2qfrG6ll9qDalxUKn1b3E=; b=moieLioJxpoBFXQsdvwMUEB3nxzCqDGoJV77P2DhHFw8SUxt7+oJW72zNS1el4FY/B dX1Qe+2wdXX61DPLLL4+qL47cCF6KaIEYXSJujWD4tBc7XiGH839Usm6jtTLPKwGunkg 1H9+PFvgFgv4KEtO6eU1jpp1LdRvLNNIOPaHeqSf4JFziEKwnlrAMV0XNLN+0iHr+qDm yMMZlY544qw+XOHec7UYlLGvdAn6H49xon/uFBRMUqetmfSL1V0AYQfGUaZK1XdGjFPg JZG8Gl/qk5/rpEFQWrbz7hUjBphPgJvrT3ZcwnrCdbHUAM2towHvkQ8Ku5Lxjmoo/RcB Hmag== X-Gm-Message-State: APjAAAXh8yLqzBuxXaOA0gytr0ZETDGlv+HOr+qyEqQnMLeFlJ9lJtst BCGKZsC0+RwVvtwsl7vrJb8UabosKWvieFQwm85ltg== X-Google-Smtp-Source: APXvYqyb1xxZ9FokZNGah/UIpAaFRfxJfgV4qwKVLTBXmZOACLUgrXPPiNzDxSLuRgoM0J8lMuMLN3unMTrUaERb+JU= X-Received: by 2002:a05:620a:910:: with SMTP id v16mr4862526qkv.194.1576587580491; Tue, 17 Dec 2019 04:59:40 -0800 (PST) MIME-Version: 1.0 References: <20191211092625.jzqx2ukphhggwavo@sirius.home.kraxel.org> <20191212094121.by7w7fywlzdfoktn@sirius.home.kraxel.org> <20191212133048.4nbmuwhbq5z2ai6o@sirius.home.kraxel.org> <20191216134728.czulyb6yvrkokrqv@sirius.home.kraxel.org> In-Reply-To: <20191216134728.czulyb6yvrkokrqv@sirius.home.kraxel.org> From: David Stevens Date: Tue, 17 Dec 2019 21:59:29 +0900 Message-ID: Subject: Re: [virtio-dev] 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::742 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: Geoffrey McRae , Hans Verkuil , Zach Reizner , Alexandre Courbot , virtio-dev@lists.oasis-open.org, qemu-devel , Alex Lau , Tomasz Figa , Keiichi Watanabe , Daniel Vetter , =?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" > > > Of course only virtio drivers would try step (2), other drivers (when > > > sharing buffers between intel gvt device and virtio-gpu for example) > > > would go straight to (3). > > > > For virtio-gpu as it is today, it's not clear to me that they're > > equivalent. As I read it, the virtio-gpu spec makes a distinction > > between the guest memory and the host resource. If virtio-gpu is > > communicating with non-virtio devices, then obviously you'd just be > > working with guest memory. But if it's communicating with another > > virtio device, then there are potentially distinct guest and host > > buffers that could be used. The spec shouldn't leave any room for > > ambiguity as to how this distinction is handled. > > Yep. It should be the host side buffer. I agree that it should be the host side buffer. I just want to make sure that the meaning of 'import' is clear, and to establish the fact that importing a buffer by uuid is not necessarily the same thing as creating a new buffer in a different device from the same sglist (for example, sharing a guest sglist might require more flushes). -David