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=-3.5 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 994AEC433E0 for ; Tue, 2 Feb 2021 09:09:36 +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 F394264F60 for ; Tue, 2 Feb 2021 09:09:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F394264F60 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]:34520 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l6rgk-0005A5-JF for qemu-devel@archiver.kernel.org; Tue, 02 Feb 2021 04:09:34 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:34180) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l6reV-0004Aj-1X for qemu-devel@nongnu.org; Tue, 02 Feb 2021 04:07:15 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:28331) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l6reR-0000Hv-SV for qemu-devel@nongnu.org; Tue, 02 Feb 2021 04:07:14 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612256830; 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: in-reply-to:in-reply-to:references:references; bh=QflWUSgUerLPNc45qh+ebbfVUtyC3tq6L53RulXx0yc=; b=Vq0wvrLD6MpHMIKtzQP5D2V25qaquUj1cGSjFyHVyVi8DUjpnjxs7U7K6B6SlYuok/PkqO MWjx60EW/9DjStktkb6DjVxSduxhixM7b9FX++Wt/3sdv4N2OPdeK+FgsBgFvLILidNzln BqGpaN65DmNkox3WGeDAUreFOd1HF/M= 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-7-ehDerYC9M0m0O810gVrDYA-1; Tue, 02 Feb 2021 04:07:04 -0500 X-MC-Unique: ehDerYC9M0m0O810gVrDYA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7FE68184214D; Tue, 2 Feb 2021 09:07:03 +0000 (UTC) Received: from oldenburg.str.redhat.com (ovpn-112-116.ams2.redhat.com [10.36.112.116]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5C64419717; Tue, 2 Feb 2021 09:06:58 +0000 (UTC) From: Florian Weimer To: Peter Maydell Subject: Re: [PATCH RFC 1/4] docs: add a table showing x86-64 ABI compatibility levels References: <20210201153606.4158076-1-berrange@redhat.com> <20210201153606.4158076-2-berrange@redhat.com> Date: Tue, 02 Feb 2021 10:06:59 +0100 In-Reply-To: (Peter Maydell's message of "Mon, 1 Feb 2021 16:53:03 +0000") Message-ID: <87lfc6zvm4.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=fweimer@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=216.205.24.124; envelope-from=fweimer@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.351, 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_H3=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: "Daniel P. =?utf-8?Q?Berrang=C3=A9?=" , Eduardo Habkost , "Michael S. Tsirkin" , Richard Henderson , QEMU Developers , Cleber Rosa , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Peter Maydell: > Apart from the QEMU/KVM specific CPU models, why is this something > we should be documenting rather than, say, the people specifying > what the ABI compatiblity levels are ? The psABI only cares about userspace, and the specification there deliberately excludes CPU features used in cryptography blocks, and features that seem unstable and likely to be disabled in firmware or future microcode updates. This seemed a good trade-off for the psABI because in userspace, run-time detection is still available, to access additional CPU features not available as part of the target x86-64 level at build time. This doesn't really work for virtualization, which also has to decide what to do with CPU features not relevant to userspace. And a decision to exclude features is final in the sense that guests cannot use the feature at all because run-time detection shows it is as unavailable. This is why a 1:1 copy of the userspace levels to virtualized machine models is not possible, I think. Thanks, Florian -- Red Hat GmbH, https://de.redhat.com/ , Registered seat: Grasbrunn, Commercial register: Amtsgericht Muenchen, HRB 153243, Managing Directors: Charles Cachera, Brian Klemm, Laurie Krebs, Michael O'Neill