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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2A6CAC433FE for ; Thu, 14 Oct 2021 13:26:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 16A38610CC for ; Thu, 14 Oct 2021 13:26:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231340AbhJNN2J (ORCPT ); Thu, 14 Oct 2021 09:28:09 -0400 Received: from mga06.intel.com ([134.134.136.31]:20887 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230049AbhJNN2H (ORCPT ); Thu, 14 Oct 2021 09:28:07 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10136"; a="288543181" X-IronPort-AV: E=Sophos;i="5.85,372,1624345200"; d="scan'208";a="288543181" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Oct 2021 06:26:02 -0700 X-IronPort-AV: E=Sophos;i="5.85,372,1624345200"; d="scan'208";a="571331074" Received: from chendan-mobl.amr.corp.intel.com (HELO [10.251.17.229]) ([10.251.17.229]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Oct 2021 06:26:00 -0700 Subject: Re: [PATCH v10 11/11] x86/tdx: Handle CPUID via #VE To: Thomas Gleixner , Kuppuswamy Sathyanarayanan , Ingo Molnar , Borislav Petkov , x86@kernel.org, Paolo Bonzini , David Hildenbrand , Andrea Arcangeli , Josh Poimboeuf , Juergen Gross , Deep Shah , VMware Inc , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel Cc: Peter H Anvin , Tony Luck , Dan Williams , Andi Kleen , Kirill Shutemov , Sean Christopherson , Kuppuswamy Sathyanarayanan , linux-kernel@vger.kernel.org References: <20211009053747.1694419-1-sathyanarayanan.kuppuswamy@linux.intel.com> <20211009053747.1694419-12-sathyanarayanan.kuppuswamy@linux.intel.com> <87a6jb7r3x.ffs@tglx> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <87a6jb7r3x.ffs@tglx> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/14/21 5:01 AM, Thomas Gleixner wrote: >> The TDX module specification [1], section titled "CPUID Virtualization" >> talks about a few more classes of CPUID handling. But, for the purposes >> of this patch, the "handled transparently" CPUID leaves are all lumped >> together because the guest handling is the same. > What means 'for the purposes of this patch'? And I have no idea what's > lumped together means either. The TDX spec talks about a several classes of CPUID bit fields. These matter in terms of trust because some of the bits can be supplied by the VMM. The original changelog here tried to draw a distinction between bits which can be supplied by the VMM ("as configured" in the spec) and those that come directly from the hardware ("native" in the spec). "Lumped together" means that although these cases are differentiated in the spec, their differences are immaterial for the purposes of this patch. I think I wrote this. I think I was trying to write it at someone who might be puzzling over the TDX spec and its table of CPUID leaves wondering why the #VE handler doesn't have cases for lots of the classes called out in the spec. > #VE is either raised on CPUID leaf/sub-leaf combinations which are not > part of the CPUID virtualization table or on request of the guest for > all CPUID invocations (either Ring0 or Ring3 or both). Yes. This changelog should also include a note about the unconditional #VE for all CPUID executions feature, noting that it is expected to be disabled for ring0. > So this patch implements the #VE handling for EXIT_REASON_CPUID by > handing it through to the hypercall, which in turn lets the TDX module > handle it by invoking the host VMM. > > So unless the guest requested #VE on all CPUID invocations it won't see > a #VE for the transparent leaf/sub-leaf combinations. #VE is raised > for the VMM handled ones which goes through the hypercall, right? Yep, that's a pretty succinct way to put it.