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 9B9D2EB64DA for ; Mon, 26 Jun 2023 09:21:44 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qDiP7-0007pY-HW; Mon, 26 Jun 2023 05:21:01 -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 1qDiP3-0007p7-Br for qemu-devel@nongnu.org; Mon, 26 Jun 2023 05:20:57 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qDiP0-0007wu-37 for qemu-devel@nongnu.org; Mon, 26 Jun 2023 05:20:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1687771253; h=from:from:reply-to: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=KPxgUMUgoaBaglrWT9PnBHEU+kMUs50BA/yptrRTKYI=; b=R3VvGWfKVdpEHWGNQVUJ6dOY19uHX2fboOGuK1LwK+RG8U3zRE8/fjHmwjyU8wdjcDndqR 8pJx8/a3Ngo9Je0aMYzQ8u09k9OLLl5YGxKSdsTTwu+UA3hvNCKH6WXTx9DU8lDYh+hz17 ObZFFcXH7+kEXAk5KMxEGO32cPL+w6M= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-618-IYLKsQ1iPluvdWCYTlgwHg-1; Mon, 26 Jun 2023 05:20:48 -0400 X-MC-Unique: IYLKsQ1iPluvdWCYTlgwHg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id EBCEF3C0F684 for ; Mon, 26 Jun 2023 09:20:47 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.55]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8C924C585A0; Mon, 26 Jun 2023 09:20:47 +0000 (UTC) Date: Mon, 26 Jun 2023 10:20:45 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Paolo Bonzini Cc: qemu-devel@nongnu.org Subject: Re: [PATCH v2 0/3] target/i386: allow using named CPU modeles with user mode emulation Message-ID: References: <20230626083317.144746-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230626083317.144746-1-pbonzini@redhat.com> User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@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=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=-1, RCVD_IN_MSPIKE_WL=-0.01, 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Jun 26, 2023 at 10:33:14AM +0200, Paolo Bonzini wrote: > When running qemu-i386 even with -cpu Nehalem (aka x86_64-v2), it raises the > warning > > TCG doesn't support requested feature: CPUID.80000001H:EDX.lm [bit 29] > > Likewise using qemu-x86_64 with -cpu Haswell, it raises warnings for > > TCG doesn't support requested feature: CPUID.01H:ECX.pcid [bit 17] > TCG doesn't support requested feature: CPUID.01H:ECX.x2apic [bit 21] > TCG doesn't support requested feature: CPUID.01H:ECX.tsc-deadline [bit 24] > TCG doesn't support requested feature: CPUID.07H:EBX.invpcid [bit 10] > > Even though x86_64-v3 is the level that qemu-user is supposed to provide. > These are two related problems: > > - for Haswell, the 4 missing features are only relevant to code running > in kernel mode; we can ignore them and mark them as supported even > though they are not. The supported features are only used to print > the warnings > > - for qemu-i386, the issue is that this emulator is restricted to running > programs on a 32-bit processor, even though it is actually emulating > programs that use the 32-bit kernel ABI on any processor. The behavior > the processor in compatibility (32-bit CS, EFER.LMA=1) mode is mostly > the same as when EFER.LMA=0 and the little code that is needed to handle > 64-bit ring-0 is even present in the qemu-i386 binary, just hidden > behind checks for HF_LMA_MASK. So, LM can also be treated as a feature > that is only relevant in kernel mode; not entirely, so this cannot yet > be extended to bsd-user, but the required changes are minimal. IMHO in this case we should hard block all named CPUs with 'lm' set from qemu-i386. It only makes sense to use named CPU models that were actually from the 32-bit era with qemu-i386. If someone wants Nehalem then they should be using qemu-x86_64. If someone wants qemu-i386 then they should be using an older named CPU model predating 'lm'. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|