From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754257AbdK1Ux0 (ORCPT ); Tue, 28 Nov 2017 15:53:26 -0500 Received: from mga01.intel.com ([192.55.52.88]:6492 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752211AbdK1UxZ (ORCPT ); Tue, 28 Nov 2017 15:53:25 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.44,468,1505804400"; d="scan'208";a="8168140" Date: Tue, 28 Nov 2017 22:53:24 +0200 From: Jarkko Sakkinen To: Sean Christopherson Cc: platform-driver-x86@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Borislav Petkov , Janakarajan Natarajan , Paolo Bonzini , "Kirill A. Shutemov" , Kyle Huey , Vikas Shivappa , Piotr Luc , Grzegorz Andrejczuk Subject: Re: [PATCH v6 04/11] x86: define IA32_FEATUE_CONTROL.SGX_LC Message-ID: <20171128205324.pqojyfqbet3h7re4@linux.intel.com> References: <20171125193132.24321-1-jarkko.sakkinen@linux.intel.com> <20171125193132.24321-5-jarkko.sakkinen@linux.intel.com> <1511889371.9392.58.camel@intel.com> <1511893683.9392.100.camel@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1511893683.9392.100.camel@intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 28, 2017 at 10:28:03AM -0800, Sean Christopherson wrote: > On Tue, 2017-11-28 at 09:16 -0800, Sean Christopherson wrote: > > On Sat, 2017-11-25 at 21:29 +0200, Jarkko Sakkinen wrote: > > > > > > When IA32_FEATURE_CONTROL.SGX_LC identifies that the root key for > > > enclave signatures can be configured either by the OS or pre-boot > > > firmware. > > > > > > If this the case, IA32_SGXLEPUBKEYHASHn MSRs (0 < n < 4) can be used > > > to > > > set the SHA256 of the root key. IA32_FEATURE_CONTROL bit 17 controls > > > whether the MSRs are writable by the OS. The pre-boot firmware can > > > decided whether to  set this bit before setting > > > IA32_FEATURE_CONTROL.LOCK. > > The commit message (feature control bit) doesn't match the patch (CPUID > > bit). > > Also, assuming this message is destined for the commit that adds SGX_LC > to feature control, I think it should first and foremost describe the > hardware behavior.  The firmware vs OS interaction and use cases are > valuable to document but IMO should come after the hardware description. > > And though it's not documented in the SDM, I think it's worthwhile to > describe the SGX activation sequence and its relationship with the SGX > MSRs, e.g. the LE hash MSRs are writable prior to SGX activation. > Without that information, it's unclear as to how the LE hash MSRs could > be different than Intel's reset value. > > So, maybe something like this? > >     After SGX is activated[1] the IA32_SGXLEPUBKEYHASHn MSRs are writable >     if and only if SGX_LC is set in the IA32_FEATURE_CONTROL MSR and the >     IA32_FEATURE_CONTROL MSR is locked, otherwise they are read-only. > >     For example, firmware can allow the OS to change the launch enclave >     root key by setting IA32_FEATURE_CONTROL.SGX_LC, and thus give the >     OS complete control over the enclaves it runs.  Alternatively, >     firmware can clear IA32_FEATURE_CONTROL.SGX_LC to lock down the root >     key and restrict the OS to running enclaves signed with the root key >     or whitelisted/trusted by a launch enclave (which must be signed with >     the root key). > >     [1] SGX related bits in IA32_FEATURE_CONTROL cannot be set until SGX >         is activated, e.g. by firmware.  SGX activation is triggered by >         setting bit 0 in MSR 0x7a.  Until SGX is activated, the LE hash >         MSRs are writable, e.g. to allow firmware to lock down the LE >         root key with a non-Intel value. Thanks I'll use this as a basis and move most of the crappy commit message to the commit (with some editing) that defines the MSRs. /Jarkko