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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id F00B6C6FA93 for ; Mon, 26 Sep 2022 18:37:51 +0000 (UTC) Received: from localhost ([::1]:41884 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ocszH-0000mZ-00 for qemu-devel@archiver.kernel.org; Mon, 26 Sep 2022 14:37:51 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:56664) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ocsuR-0003v2-BF for qemu-devel@nongnu.org; Mon, 26 Sep 2022 14:32:51 -0400 Received: from madras.collabora.co.uk ([46.235.227.172]:43120) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ocsuO-00023A-BO for qemu-devel@nongnu.org; Mon, 26 Sep 2022 14:32:50 -0400 Received: from [192.168.2.145] (unknown [109.252.124.206]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: dmitry.osipenko) by madras.collabora.co.uk (Postfix) with ESMTPSA id B47D9660036F; Mon, 26 Sep 2022 19:32:43 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1664217164; bh=COIlK3XoxMzL90X5+Jk69G+Q1JKus93OW9r9uLntouo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=RIQY4kIifcE97352IFCJM5zV1Cr6HsyBKtjPJF42YyZdPeBONu+QN2LzopjcydRsA TWLbWs0Jw7pDToRP8haWZlE4b80IA82Ph5bUYhMfCQn/fq0EPLXckqFpnM89aRk6j5 mpEtCj9z8xhUXlPNzhY33jeZdizeo4+MrqECffYq3xgCoSlBKbBHYxHZFW12UqWIh5 GeOyQNQQZgcFH1pQXKkLOAxhkWxgowOmdsJaNBhdHd7fstEriP2lXWsQMaPifrXG09 F/t1A7rOyjrtWqq86eZVvjhZES04GYV3dAOCYq86wiX6bIZ2HOz9GuBCC962eIP3Py GrakcISqWewsg== Message-ID: <6fe0d770-1a95-3d8f-6a75-a596f26aad54@collabora.com> Date: Mon, 26 Sep 2022 21:32:40 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.1 Subject: Re: [PATCH v2 4/4] virtio-gpu: Don't require udmabuf when blob support is enabled To: Gerd Hoffmann , Antonio Caggiano Cc: qemu-devel@nongnu.org, gert.wollny@collabora.com, "Michael S. Tsirkin" References: <20220913105022.81953-1-antonio.caggiano@collabora.com> <20220913105022.81953-5-antonio.caggiano@collabora.com> <20220923123219.ofn2ygm4knljo6w2@sirius.home.kraxel.org> Content-Language: en-US From: Dmitry Osipenko In-Reply-To: <20220923123219.ofn2ygm4knljo6w2@sirius.home.kraxel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=46.235.227.172; envelope-from=dmitry.osipenko@collabora.com; helo=madras.collabora.co.uk X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-2.319, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 9/23/22 15:32, Gerd Hoffmann wrote: > On Tue, Sep 13, 2022 at 12:50:22PM +0200, Antonio Caggiano wrote: >> From: Dmitry Osipenko >> >> Host blobs don't need udmabuf, it's only needed by guest blobs. The host >> blobs are utilized by the Mesa virgl driver when persistent memory mapping >> is needed by a GL buffer, otherwise virgl driver doesn't use blobs. >> Persistent mapping support bumps GL version from 4.3 to 4.5 in guest. >> Relax the udmabuf requirement. > > What about blob=on,virgl=off? > > In that case qemu manages the resources and continued to require > udmabuf. The udmabuf is used only by the blob resource-creation command in Qemu. I couldn't find when we could hit that udmabuf code path in Qemu because BLOB_MEM_GUEST resource type is used only by crosvm+Venus when crosvm uses a dedicated render-server for virglrenderer. Summarizing: - only BLOB_MEM_GUEST resources require udmabuf - /dev/udmabuf isn't accessible by normal user - udmabuf driver isn't shipped by all of the popular Linux distros, for example Debian doesn't ship it Because of all of the above, I don't think it makes sense to hard-require udmabuf at the start of Qemu. It's much better to fail resource creation dynamically. -- Best regards, Dmitry