From patchwork Thu Dec 5 22:33:39 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eduardo Habkost X-Patchwork-Id: 1204848 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.b="LP6zaUom"; dkim-atps=neutral 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 ozlabs.org (Postfix) with ESMTPS id 47TVrz143xz9sPW for ; Fri, 6 Dec 2019 09:34:41 +1100 (AEDT) Received: from localhost ([::1]:33364 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iczhl-00080k-Rb for incoming@patchwork.ozlabs.org; Thu, 05 Dec 2019 17:34:37 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:33724) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iczh8-0007zy-C5 for qemu-devel@nongnu.org; Thu, 05 Dec 2019 17:34:00 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iczh1-0005ik-WC for qemu-devel@nongnu.org; Thu, 05 Dec 2019 17:33:54 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:33519 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 1iczgz-0005ep-1q for qemu-devel@nongnu.org; Thu, 05 Dec 2019 17:33:50 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1575585227; 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; bh=HWMtsqko9C2dTYmM1o5ZIxnFXtXC2FTQMR5CQothB7s=; b=LP6zaUombxh/2BvqKv9i5MkinwY7xK5NxIRUUoOnS6wkAAV6Eo1nOGQJquyLcH7y7iE4ps uR6geSdvQjlOjHnsIu+gbQeRl74MP2aWg/XtuD0nS+2/pSQBpMO5uUgYMqh/zA2h+7nSYt 4kfDHW5ED5rsSMPZGPYC7gCPZqmtopo= 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-145-q8yD5t2aOqy2FN8xu6vG6A-1; Thu, 05 Dec 2019 17:33:46 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DDA77101F4F2; Thu, 5 Dec 2019 22:33:44 +0000 (UTC) Received: from localhost (ovpn-116-90.gru2.redhat.com [10.97.116.90]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0018A5D6BB; Thu, 5 Dec 2019 22:33:40 +0000 (UTC) From: Eduardo Habkost To: qemu-devel@nongnu.org Subject: [PATCH] i386: Resolve CPU models to v1 by default Date: Thu, 5 Dec 2019 19:33:39 -0300 Message-Id: <20191205223339.764534-1-ehabkost@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-MC-Unique: q8yD5t2aOqy2FN8xu6vG6A-1 X-Mimecast-Spam-Score: 0 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 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: "Daniel P. Berrange" , libvir-list@redhat.com, qemu-stable@nongnu.org, Paolo Bonzini , Jiri Denemark , Richard Henderson Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.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=1779078 Signed-off-by: Eduardo Habkost --- I don't think this should block QEMU 4.2.0 from being tagged. The bug is present since 4.1.0, so we can fix it in 4.1.2 and/or 4.2.1. --- 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 4b4b7425ac..b42d8b3c5f 100644 --- a/qemu-deprecated.texi +++ b/qemu-deprecated.texi @@ -374,6 +374,14 @@ guarantees must resolve the CPU model aliases using te ``alias-of'' field returned by the ``query-cpu-definitions'' QMP command. +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. + @node Recently removed features @appendix Recently removed features diff --git a/target/i386/cpu.c b/target/i386/cpu.c index 69f518a21a..54e7f18a09 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -3924,7 +3924,13 @@ static PropValue tcg_default_props[] = { }; -X86CPUVersion default_cpu_version = 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 = 1; void x86_cpu_set_default_version(X86CPUVersion version) {