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 90203C77B7A for ; Wed, 17 May 2023 15:54:41 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pzJSR-0003Ku-8h; Wed, 17 May 2023 11:52:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pzJSO-0003Jj-3i for qemu-devel@nongnu.org; Wed, 17 May 2023 11:52:52 -0400 Received: from mail-wr1-x432.google.com ([2a00:1450:4864:20::432]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1pzJSM-0005v0-EW for qemu-devel@nongnu.org; Wed, 17 May 2023 11:52:51 -0400 Received: by mail-wr1-x432.google.com with SMTP id ffacd0b85a97d-3063433fa66so635563f8f.3 for ; Wed, 17 May 2023 08:52:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1684338768; x=1686930768; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:user-agent:from:to:cc:subject:date:message-id:reply-to; bh=2zgawbbiH3ZN+t5cl5i5se7wIX3B/JzZA+6PRyvIIdQ=; b=g5vI9spJJGk0AQg2nrDscgqmqP0hfliUsHdlmHIo3Us/3MCHru8MSL5VhuY5GT2/mq dRoS9rGKH+DSY0Pk6SGac+3nIrPcqrixW/J4kbvJqqzBVSCbZ8xOFTu/ib1xQ7zviDZk ibs2kc+8BOqHSss7aGDvVd5cDpfR14sdXJxylUPWqT/o/PqQ4hY9XSf+wHEmCaQh4q94 FdFDSJGxvGseU3ZcQCFrHKeAwnWn++N0N3NhMWfDwCBhXlwgBEWuTh1Zzuy6AvkocsEa JF4hTrpK1NZCFMuLudbaFaQY4XnlK7TfXMkMNOZzzhktmkAMiz6g0Gc46Sl6Jd0zwx3/ nMSQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684338768; x=1686930768; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:user-agent:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=2zgawbbiH3ZN+t5cl5i5se7wIX3B/JzZA+6PRyvIIdQ=; b=de2kcFJzbJEdGfbJ/au1QZmZx48mHg/CJyxkG8OxUe6siURZexhh/aLP0rqnk2GDTa nUyk/ichBIn9sh1xLqskYvv2UrcF/ajoy4Vmw/hc6MCx8061DkPWFjbAkKku7wsD9Ik6 rpvYgnA1nchjxIygSm0ozPDPAFY+24EOtiMAIQxHYmumoJxoyPO0QXVMMJ1EomHxSYux Qx5NjphsPJ2piK23cyo2W9YL+1Fb+E4g0VFcSRT0DAdECIujISdo3btX6HqB82O3bEph GKbixsMyCYDLzEbaYf66WL2FtTiWYzs3SH99Mey4IpyIFaUxWYlsnO/M8I5LRdzPm4uA kZbQ== X-Gm-Message-State: AC+VfDzskmrx6nQgNWKlkuGI5+P/y+OtOvctIN5VfiypSvI90R+N917b cwlNKVyyZ6+nH2kJHH6FaukhL4XP/vPD+zLqUBzyEQ== X-Google-Smtp-Source: ACHHUZ7q2z3P6UZkiBWionaRCIoCzNwGj7Sy+we/QRxvSxXiETH9tC1liVIInk17lzo3LqqEPXPiVg== X-Received: by 2002:a5d:58e6:0:b0:309:33c4:52e1 with SMTP id f6-20020a5d58e6000000b0030933c452e1mr838763wrd.64.1684338767816; Wed, 17 May 2023 08:52:47 -0700 (PDT) Received: from zen.linaroharston ([85.9.250.243]) by smtp.gmail.com with ESMTPSA id j11-20020adff54b000000b003062c609115sm3235414wrp.21.2023.05.17.08.52.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 May 2023 08:52:47 -0700 (PDT) Received: from zen (localhost [127.0.0.1]) by zen.linaroharston (Postfix) with ESMTP id 0148D1FFBB; Wed, 17 May 2023 16:52:47 +0100 (BST) User-agent: mu4e 1.11.6; emacs 29.0.91 From: Alex =?utf-8?Q?Benn=C3=A9e?= To: QEMU Developers Cc: Stefan Hajnoczi , virtio-fs@redhat.com, Erik Schilling Subject: Status of DAX for virtio-fs/virtiofsd? Date: Wed, 17 May 2023 16:23:46 +0100 Message-ID: <87v8grlzu9.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=2a00:1450:4864:20::432; envelope-from=alex.bennee@linaro.org; helo=mail-wr1-x432.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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-bounces+qemu-devel=archiver.kernel.org@nongnu.org Hi, I remember from the dim and distant past (probably a KVM Forum) that one of the touted features of virtio-fs was the ability to get memory efficiency savings by having a direct memory mapping the host pages into the guest address space. AFAICT the kernel side was merged a while ago, see 22f3787 (virtiofs: set up virtio_fs dax_device) and related. However when investigating what would be needed to support this for Xen guests using virtio-fs we were confused as to what else was needed. There were some patches for the old C daemon: Subject: [PATCH v3 00/26] virtiofs dax patches Date: Wed, 28 Apr 2021 12:00:34 +0100 [thread overview] Message-ID: <20210428110100.27757-1-dgilbert@redhat.com> although they look like they were never merged and the C version of virtiofsd has since been dropped from tools. Looking at the supporting rust code (vhost_user/message.rs) there are a number of additional messages: /// Virtio-fs draft: map file content into the window. FS_MAP =3D 6, /// Virtio-fs draft: unmap file content from the window. FS_UNMAP =3D 7, /// Virtio-fs draft: sync file content. FS_SYNC =3D 8, /// Virtio-fs draft: perform a read/write from an fd directly to GPA. FS_IO =3D 9, /// Upper bound of valid commands. MAX_CMD =3D 10, that don't appear in the current canonical vhost-user reference in the QEMU repository and the QEMU code certainly doesn't have implementations for any of them. So I have some questions: * What VMM/daemon combinations has DAX been tested on? * Isn't it time the vhost-user spec is updated? * Is anyone picking up Dave's patches for the QEMU side of support? Thanks, --=20 Alex Benn=C3=A9e Virtualisation Tech Lead @ Linaro