Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751522AbcJJE7b (ORCPT ); Mon, 10 Oct 2016 00:59:31 -0400 Received: from mga14.intel.com ([192.55.52.115]:17439 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750881AbcJJE7a (ORCPT ); Mon, 10 Oct 2016 00:59:30 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.31,470,1473145200"; d="scan'208";a="1068309343" Date: Mon, 10 Oct 2016 07:59:25 +0300 From: Jarkko Sakkinen To: "Winkler, Tomas" Cc: Jason Gunthorpe , "moderated list:TPM DEVICE DRIVER" , open list Subject: Re: [tpmdd-devel] [PATCH RFC 1/3] tpm_crb: expand struct crb_control_area to struct crb_regs Message-ID: <20161010045925.GA5671@intel.com> References: <1475972112-2819-1-git-send-email-jarkko.sakkinen@linux.intel.com> <1475972112-2819-2-git-send-email-jarkko.sakkinen@linux.intel.com> <20161009014256.GA8210@obsidianresearch.com> <20161009093818.GG31891@intel.com> <20161009164905.GA12551@obsidianresearch.com> <20161009183232.GA27764@intel.com> <20161009183358.GB27764@intel.com> <20161009230737.GA23823@obsidianresearch.com> <5B8DA87D05A7694D9FA63FD143655C1B542F7497@hasmsx108.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5B8DA87D05A7694D9FA63FD143655C1B542F7497@hasmsx108.ger.corp.intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2622 Lines: 63 On Mon, Oct 10, 2016 at 12:25:11AM +0000, Winkler, Tomas wrote: > > > > -----Original Message----- > > From: Jason Gunthorpe [mailto:jgunthorpe@obsidianresearch.com] > > Sent: Monday, October 10, 2016 02:08 > > To: Jarkko Sakkinen > > Cc: moderated list:TPM DEVICE DRIVER ; > > open list > > Subject: Re: [tpmdd-devel] [PATCH RFC 1/3] tpm_crb: expand struct > > crb_control_area to struct crb_regs > > > > On Sun, Oct 09, 2016 at 09:33:58PM +0300, Jarkko Sakkinen wrote: > > > > > > Sorry I missed this part. > > > > > > > > Here are the constraints for existing hardware: > > > > > > > > 1. All the existing CRB start only hardware has the iomem covering the > > > > control area and registers for multiple localities. > > > > 2. All the existing ACPI start hardware has only the control area. > > > > > > > > If you assume that SSDT does not have malicous behavior caused by > > > > either a BIOS bug or maybe a rootkit, then the current patch works > > > > for all the existing hardware. > > > > > > > > To counter-measure for unexpected behavior in non-existing hardware > > > > and buggy or malicious firmware it probably make sense to use > > > > crb_map_res to validate the part of the CRB registers that is not > > > > part of the control area. > > > > I don't know how much I'd assume BIOS authors do what you think - the spec I > > saw for this seems very vauge. > > > > Certainly checking that locality region falls within the acpi mapping seems > > essential. > > > > > > Doing it in the way you proposed does not work for ACPI start devices. > > > > > > > > For them it should be done in the same way as I'm doing in the > > > > existing patch as for ACPI start devices the address below the > > > > control area are never accessed. Having a separate crb_map_res for > > > > CRB start only devices is sane thing to do for validation. > > > > > > Alternative is to do two structures crb_regs_head and crb_regs_tail, > > > which might be cleaner. I'm fine with going either route. > > > > Since the iomem doesn't actually exist for a configuration having two pointers > > is the better choice. Make sure one is null for the configuration that does not > > support it. > > > > The negative offset thing is way too subtle. > > I addition I believe it should be always on offset FED4_0xxxh by the > Spec, so all this arithmetic is a bit of overkill. It's all done to workaround ACPI start. Even if CRB start devices would always be in that offset it still would be needed. > Thanks > Tomas /Jarkko