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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 12 Mar 2019 16:59:42 -0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x2CGxfKE35193084 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 12 Mar 2019 16:59:41 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5F74411C05B; Tue, 12 Mar 2019 16:59:41 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 031C511C054; Tue, 12 Mar 2019 16:59:40 +0000 (GMT) Received: from localhost.localdomain (unknown [9.80.93.217]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 12 Mar 2019 16:59:39 +0000 (GMT) Subject: Re: [PATCH] tpm: Make timeout logic simpler and more robust From: Mimi Zohar To: James Bottomley , Jarkko Sakkinen , Peter =?ISO-8859-1?Q?H=FCwe?= 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 Date: Tue, 12 Mar 2019 12:59:29 -0400 In-Reply-To: <1552401766.3083.3.camel@HansenPartnership.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> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.20.5 (3.20.5-1.fc24) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19031216-0020-0000-0000-00000321B9A2 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19031216-0021-0000-0000-00002173E630 Message-Id: <1552409969.24794.68.camel@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-03-12_09:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903120116 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2019-03-12 at 07:42 -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. James, I thought Peter sent you a tis "debug" tool to help you debug the problem you're seeing.  Whatever happened? Mimi