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=-6.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=ham 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 0CC33C2D0C8 for ; Fri, 20 Dec 2019 19:22:20 +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 CE596206DA for ; Fri, 20 Dec 2019 19:22:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="I6Wr3L5d" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CE596206DA 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]:60840 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iiNqs-0000Dg-Au for qemu-devel@archiver.kernel.org; Fri, 20 Dec 2019 14:22:18 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:60476) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iiNpP-00072z-5o for qemu-devel@nongnu.org; Fri, 20 Dec 2019 14:20:48 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iiNpN-0005jC-QH for qemu-devel@nongnu.org; Fri, 20 Dec 2019 14:20:47 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:46093 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iiNpN-0005gf-Lg for qemu-devel@nongnu.org; Fri, 20 Dec 2019 14:20:45 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1576869644; 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=aAIg1jndVqtbahW24LK42vpmp+cvAhx5zyExwQTzPOg=; b=I6Wr3L5dypJxgFaVU1aqdf2Pt9srGOQKVgFBNv2wZfettIlYvp3KzKqVhdIl8fOhszDVRq oip9Wa983GWdSDnPvibw8v6lfiK0s+DUXtR9/k3E8tgCn0SPZWBJ1lterOBXpEdDZQ4TiD AeHm5lK3qJoKYgBfxCRGu43g7+DPLG4= 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-188-y0H0z--FOO2fBnQyBan3Qg-1; Fri, 20 Dec 2019 14:20:42 -0500 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 99595DB23; Fri, 20 Dec 2019 19:20:41 +0000 (UTC) Received: from localhost (ovpn-116-10.gru2.redhat.com [10.97.116.10]) by smtp.corp.redhat.com (Postfix) with ESMTP id 96E1E5C1B0; Fri, 20 Dec 2019 19:20:38 +0000 (UTC) From: Eduardo Habkost To: qemu-devel@nongnu.org, Peter Maydell Subject: [PULL 1/3] i386: Resolve CPU models to v1 by default Date: Fri, 20 Dec 2019 16:20:29 -0300 Message-Id: <20191220192031.2226378-2-ehabkost@redhat.com> In-Reply-To: <20191220192031.2226378-1-ehabkost@redhat.com> References: <20191220192031.2226378-1-ehabkost@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-MC-Unique: y0H0z--FOO2fBnQyBan3Qg-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.120 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: Paolo Bonzini , "Michael S. Tsirkin" , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" When using `query-cpu-definitions` using `-machine none`, QEMU is resolving all CPU models to their latest versions. The actual CPU model version being used by another machine type (e.g. `pc-q35-4.0`) might be different. In theory, this was OK because the correct CPU model version is returned when using the correct `-machine` argument. Except that in practice, this breaks libvirt expectations: libvirt always use `-machine none` when checking if a CPU model is runnable, because runnability is not expected to be affected when the machine type is changed. For example, when running on a Haswell host without TSX, Haswell-v4 is runnable, but Haswell-v1 is not. On those hosts, `query-cpu-definitions` says Haswell is runnable if using `-machine none`, but Haswell is actually not runnable using any of the `pc-*` machine types (because they resolve Haswell to Haswell-v1). In other words, we're breaking the "runnability guarantee" we promised to not break for a few releases (see qemu-deprecated.texi). To address this issue, change the default CPU model version to v1 on all machine types, so we make `query-cpu-definitions` output when using `-machine none` match the results when using `pc-*`. This will change in the future (the plan is to always return the latest CPU model version if using `-machine none`), but only after giving libvirt the opportunity to adapt. Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=3D1779078 Signed-off-by: Eduardo Habkost Message-Id: <20191205223339.764534-1-ehabkost@redhat.com> Signed-off-by: Eduardo Habkost --- qemu-deprecated.texi | 8 ++++++++ target/i386/cpu.c | 8 +++++++- 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi index 62680f7bd5..7b94653cef 100644 --- a/qemu-deprecated.texi +++ b/qemu-deprecated.texi @@ -367,6 +367,14 @@ guarantees must resolve the CPU model aliases using te ``alias-of'' field returned by the ``query-cpu-definitions'' QMP command. =20 +While those guarantees are kept, the return value of +``query-cpu-definitions'' will have existing CPU model aliases +point to a version that doesn't break runnability guarantees +(specifically, version 1 of those CPU models). In future QEMU +versions, aliases will point to newer CPU model versions +depending on the machine type, so management software must +resolve CPU model aliases before starting a virtual machine. + =20 @node Recently removed features @appendix Recently removed features diff --git a/target/i386/cpu.c b/target/i386/cpu.c index 0a9ac65974..ba5e9d5d6b 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -3981,7 +3981,13 @@ static PropValue tcg_default_props[] =3D { }; =20 =20 -X86CPUVersion default_cpu_version =3D CPU_VERSION_LATEST; +/* + * We resolve CPU model aliases using -v1 when using "-machine + * none", but this is just for compatibility while libvirt isn't + * adapted to resolve CPU model versions before creating VMs. + * See "Runnability guarantee of CPU models" at * qemu-deprecated.texi. + */ +X86CPUVersion default_cpu_version =3D 1; =20 void x86_cpu_set_default_version(X86CPUVersion version) { --=20 2.23.0