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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 326AAC10F27 for ; Tue, 10 Mar 2020 17:23:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0499421927 for ; Tue, 10 Mar 2020 17:23:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="jC2v5tmm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726491AbgCJRX4 (ORCPT ); Tue, 10 Mar 2020 13:23:56 -0400 Received: from mail-il1-f195.google.com ([209.85.166.195]:36706 "EHLO mail-il1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726283AbgCJRX4 (ORCPT ); Tue, 10 Mar 2020 13:23:56 -0400 Received: by mail-il1-f195.google.com with SMTP id h3so1439787ils.3 for ; Tue, 10 Mar 2020 10:23:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=bpKs3XJUi+EzrxrD69z2rWEMUDijI2aX+JxbzZCOheM=; b=jC2v5tmmuEnmUgDs+1o340Pp6muc2ypEpD8eaP6r2cPOyHT0UQ2PlIn/QtNGxkE4+8 cASs91MnMeo8ZYxW2c5PAIkJ0SDlxhG3iJTSsvPlU5s080/QYJohXagrGCH/GzpvvT98 WHcXWwupWcsc+f8H82YAAoIrwBgVLBphe07lLJBYJ8HdcmX9XBOxeechO/XaWNXYi8YE Aa0OUiQKyYWYwEQds8gPprxAGBjI+WvtYntOAB9plQyYyp/YDkhYYJzjDXUGcvMxQWsD cxjeiHchLTmwjy7F8sJse27h8pR8rUkqcBaVeAUD8fgXZC+ckz7ZSMd/nZ5nPvp6jypt Kg3w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=bpKs3XJUi+EzrxrD69z2rWEMUDijI2aX+JxbzZCOheM=; b=VTmHF+ODJ9Bt3Td4Hgup8wabyAXMhx1GbMFhK7QhYNhyhi0O2CUDZtqLtTsPVgRs84 8gT+EThPkLsK56/74TAtkZ8xSsq3F0A6bLRII4fg5+EuJBE6rOF9u3ee0AfyKly/l9Oh PrEDuXyhD3UFBPcHeQjEP72mpmQ8dSo0o744y//0FEyhrvTijzlxlMTZOQ491Lv8kM5U o+lDC1x4CHy2Ncz6xn7o5e43FxU2ixk/Eviyre8OJ/ycXDinyXRuxi0s48S5h7yQqdLR RxMfzRmecPfSwpaZV2D0b+ubbM1qOEC076dhWkeUJG7rgR60mdQo52H+d/vQndQS3mt0 ebsQ== X-Gm-Message-State: ANhLgQ07u8JB+UHjt7trltws+r30ef1EkE3xdAwzPv6aHP9Poi7AHCgf 55hzrtYdoiCI4oBu4HH+c02uOkhdHaq7/IAWCSx4BXXr X-Google-Smtp-Source: ADFU+vsdimCS3ju3X6q4TFVr0q8tJXbwYngqSmKvAnDqE7FFDwCj2Y7m2zWw0oFBeuLMLbJXXOmYlKV7766rSe/gNpI= X-Received: by 2002:a92:3c04:: with SMTP id j4mr12290505ila.108.1583861035356; Tue, 10 Mar 2020 10:23:55 -0700 (PDT) MIME-Version: 1.0 References: <20200305013437.8578-1-sean.j.christopherson@intel.com> <20200305013437.8578-5-sean.j.christopherson@intel.com> <20200305192532.GN11500@linux.intel.com> <20200305215149.GS11500@linux.intel.com> <5567edf6-a04c-5810-8ed5-78a0db14b202@redhat.com> <20200310171017.GC9305@linux.intel.com> In-Reply-To: <20200310171017.GC9305@linux.intel.com> From: Jim Mattson Date: Tue, 10 Mar 2020 10:23:44 -0700 Message-ID: Subject: Re: [PATCH v2 4/7] KVM: x86: Fix CPUID range checks for Hypervisor and Centaur classes To: Sean Christopherson Cc: Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Joerg Roedel , kvm list , LKML , Pu Wen Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 10, 2020 at 10:10 AM Sean Christopherson wrote: > > On Fri, Mar 06, 2020 at 10:03:37AM +0100, Paolo Bonzini wrote: > > On 05/03/20 22:51, Sean Christopherson wrote: > > >> Ah. So cross-vendor CPUID specifications are not supported? > > > Cross-vendor CPUID is sort of allowed? E.g. this plays nice with creating > > > a Centaur CPU on an Intel platform. My interpretation of GET_SUPPORTED... > > > is that KVM won't prevent enumerating what you want in CPUID, but it only > > > promises to correctly support select leafs. > > > > But in practice does this change anything? If the vendor is not Centaur > > it's unlikely that there is a 0xc0000000 leaf. The 0x80000000 bound is > > certainly not going to be at 0xc0000000 or beyond, and likewise to 0xc0000000 > > bound is not going to be at 0xd0000000 or beyond. So I'm not sure if > > anything is lost from this simplification: > > Probably not? But in the unlikely scenario that Intel wants to add a CPUID > leaf above 0xc0000000, I don't want to have to explain that it might cause > problems for KVM guests because I added code to emulate (alleged) Centaur > behavior for virtual Intel CPUs. And there is some precedent for that, with the 0x20000000 leaves.