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=-3.6 required=3.0 tests=BAYES_00,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 994D9C07E9B for ; Tue, 20 Jul 2021 11:34:12 +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 11E2361009 for ; Tue, 20 Jul 2021 11:34:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 11E2361009 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:38038 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1m5o0o-0000sd-LL for qemu-devel@archiver.kernel.org; Tue, 20 Jul 2021 07:34:10 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34436) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m5nzg-00005t-Oz for qemu-devel@nongnu.org; Tue, 20 Jul 2021 07:33:00 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:59097) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m5nze-0004Ax-PI for qemu-devel@nongnu.org; Tue, 20 Jul 2021 07:32:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1626780776; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9jrBhpn/nnzHOHqTRJ0OG6sWhnYBKzVEPo1aQTDHuNA=; b=N4GjwS9N1u8sHi+dFQ2VfguOkaQ3xZg6LPy9qk34RYlIHjY/KLbBukFFBC1B4rzMrbZGKi kZqLZMJlLRvGCpY6gUUeErRf+NRO7VgZuTJ8x+CAPcFQqHwo2rEdUG/8dFGpF7Z2U8eO5i thZyJL1szuLOPwxG1cxNGa6RH+abSL0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-515-SbXWhBcPPpSvo4tb7Ha39w-1; Tue, 20 Jul 2021 07:32:55 -0400 X-MC-Unique: SbXWhBcPPpSvo4tb7Ha39w-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6197310557DC for ; Tue, 20 Jul 2021 11:32:53 +0000 (UTC) Received: from redhat.com (ovpn-113-81.ams2.redhat.com [10.36.113.81]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5892F78ABC; Tue, 20 Jul 2021 11:32:45 +0000 (UTC) Date: Tue, 20 Jul 2021 13:32:43 +0200 From: Kevin Wolf To: Stefan Hajnoczi Subject: Re: [PATCH v3 0/3] vhost-user: warn when guest RAM is not shared Message-ID: References: <20210714092946.569516-1-stefanha@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210714092946.569516-1-stefanha@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.474, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Laurent Vivier , Thomas Huth , "Michael S. Tsirkin" , qemu-devel@nongnu.org, Paolo Bonzini , =?iso-8859-1?Q?Marc-Andr=E9?= Lureau Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 14.07.2021 um 11:29 hat Stefan Hajnoczi geschrieben: > v3: > * Rebased > v2: > * Clarify that object-memory-memfd enables share=on by default [Marc-André] > * Rebased > > vhost-user requires -object memory-backend-*,share=on option so that QEMU uses > mmap(MAP_SHARED) on guest RAM that is shared with the vhost-user device backend > process. This is needed so the QEMU process sees changes made by the vhost-user > device backend process, and vice versa. > > Today QEMU and the vhost-user device process will start up and then fail with a > confusing error message if the user forgot to specify share=on. > > This patch series adds a warning letting the user know that share=on is > required. Hmm... This seems to work when I use shared=off for the memory backend, even though the error message is easy to miss because more error messages follow: $ LANG=C build/qemu-system-x86_64 -object memory-backend-memfd,id=mem,size=1G,share=off -m 1G -M memory-backend=mem -chardev socket,path=/tmp/vhost.sock,id=vhost1 -device vhost-user-blk-pci,chardev=vhost1 qemu-system-x86_64: -device vhost-user-blk-pci,chardev=vhost1: warning: Found vhost-user memory region without MAP_SHARED (did you forget -object memory-*,share=on?) qemu-system-x86_64: Unexpected end-of-file before all data were read qemu-system-x86_64: Failed to set msg fds. qemu-system-x86_64: vhost VQ 0 ring restore failed: -1: Resource temporarily unavailable (11) However, if I don't create the memory backend at all (which is probably the most common error users will make), then the new message isn't printed: $ LANG=C build/qemu-system-x86_64 -m 1G -chardev socket,path=/tmp/vhost.sock,id=vhost1 -device vhost-user-blk-pci,chardev=vhost1 qemu-system-x86_64: Unexpected end-of-file before all data were read qemu-system-x86_64: Failed to set msg fds. qemu-system-x86_64: vhost VQ 0 ring restore failed: -1: Resource temporarily unavailable (11) Wouldn't we want a warning for the second case, too? Kevin