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=ham 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 B0067C43381 for ; Tue, 12 Mar 2019 12:50:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 88BA12147A for ; Tue, 12 Mar 2019 12:50:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726743AbfCLMuh (ORCPT ); Tue, 12 Mar 2019 08:50:37 -0400 Received: from mga04.intel.com ([192.55.52.120]:45513 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725844AbfCLMug (ORCPT ); Tue, 12 Mar 2019 08:50:36 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Mar 2019 05:50:35 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,471,1544515200"; d="scan'208";a="281945649" Received: from skalur-mobl.amr.corp.intel.com (HELO localhost) ([10.249.254.173]) by orsmga004.jf.intel.com with ESMTP; 12 Mar 2019 05:50:30 -0700 Date: Tue, 12 Mar 2019 14:50:28 +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: <20190312125028.GC9243@linux.intel.com> References: <358e89ed2b766d51b5f57abf31ab7a925ac63379.1552348123.git.calvinowens@fb.com> <1552350463.23859.8.camel@HansenPartnership.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1552350463.23859.8.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-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. /Jarkko