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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 4F9EAC43381 for ; Tue, 12 Mar 2019 15:39:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2AFC2205F4 for ; Tue, 12 Mar 2019 15:39:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726649AbfCLPjh (ORCPT ); Tue, 12 Mar 2019 11:39:37 -0400 Received: from mga01.intel.com ([192.55.52.88]:49949 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726174AbfCLPjh (ORCPT ); Tue, 12 Mar 2019 11:39:37 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Mar 2019 08:39:37 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,471,1544515200"; d="scan'208";a="140141856" Received: from djustese-mobl1.ger.corp.intel.com (HELO localhost) ([10.249.254.184]) by FMSMGA003.fm.intel.com with ESMTP; 12 Mar 2019 08:39:32 -0700 Date: Tue, 12 Mar 2019 17:39:31 +0200 From: Jarkko Sakkinen To: James Bottomley Cc: Calvin Owens , Peter Huewe , Jason Gunthorpe , Arnd Bergmann , Greg Kroah-Hartman , linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH] tpm: Make timeout logic simpler and more robust Message-ID: <20190312153931.GA9927@linux.intel.com> References: <358e89ed2b766d51b5f57abf31ab7a925ac63379.1552348123.git.calvinowens@fb.com> <1552350463.23859.8.camel@HansenPartnership.com> <20190312125028.GC9243@linux.intel.com> <1552401766.3083.3.camel@HansenPartnership.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1552401766.3083.3.camel@HansenPartnership.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On Tue, Mar 12, 2019 at 07:42:46AM -0700, James Bottomley wrote: > On Tue, 2019-03-12 at 14:50 +0200, Jarkko Sakkinen wrote: > > On Mon, Mar 11, 2019 at 05:27:43PM -0700, James Bottomley wrote: > > > On Mon, 2019-03-11 at 16:54 -0700, Calvin Owens wrote: > > > > e're having lots of problems with TPM commands timing out, and > > > > we're seeing these problems across lots of different hardware > > > > (both v1/v2). > > > > > > > > I instrumented the driver to collect latency data, but I wasn't > > > > able to find any specific timeout to fix: it seems like many of > > > > them are too aggressive. So I tried replacing all the timeout > > > > logic with a single universal long timeout, and found that makes > > > > our TPMs 100% reliable. > > > > > > > > Given that this timeout logic is very complex, problematic, and > > > > appears to serve no real purpose, I propose simply deleting all > > > > of it. > > > > > > "no real purpose" is a bit strong given that all these timeouts are > > > standards mandated. The purpose stated by the standards is that > > > there needs to be a way of differentiating the TPM crashed from the > > > TPM is taking a very long time to respond. For a normally > > > functioning TPM it looks complex and unnecessary, but for a > > > malfunctioning one it's a lifesaver. > > > > Standards should be only followed when they make practical sense and > > ignored when not. The range is only up to 2s anyway. > > I don't disagree ... and I'm certainly not going to defend the TCG > because I do think the complexity of some of its standards contributed > to the lack of use of TPM 1.2. > > However, I am saying we should root cause this problem rather than take > a blind shot at the apparent timeout complexity. My timeout > instability is definitely related to the polling adjustments, so it's > not unreasonable to think Facebooks might be as well. Yeah, referring to my review comment, I think the very first thing that should be done is to split patch into two. Then we can probably give better feedback. /Jarkko