Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751434AbdIOPTp (ORCPT ); Fri, 15 Sep 2017 11:19:45 -0400 Received: from mga06.intel.com ([134.134.136.31]:22618 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751152AbdIOPTo (ORCPT ); Fri, 15 Sep 2017 11:19:44 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.42,397,1500966000"; d="scan'208";a="1172571616" Date: Fri, 15 Sep 2017 08:19:26 -0700 From: Jarkko Sakkinen To: Nayna Jain Cc: Peter Huewe , tpmdd-devel@lists.sourceforge.net, tpmdd@selhorst.net, jgunthorpe@obsidianresearch.com, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ima-devel@lists.sourceforge.net, patrickc@us.ibm.com Subject: Re: [PATCH v2 1/4] tpm: ignore burstcount to improve tpm_tis send() performance. Message-ID: <20170915151926.nu6awoab24ohbrew@linux.intel.com> References: <20170906125643.5070-1-nayna@linux.vnet.ibm.com> <20170906125643.5070-2-nayna@linux.vnet.ibm.com> <20170912222010.ltm76m5vy2kupydi@linux.intel.com> <20170913231007.22yb57hlx45aznt6@linux.intel.com> <3c83ac72-59cc-f6c8-26ca-b7f8a8887d39@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3c83ac72-59cc-f6c8-26ca-b7f8a8887d39@linux.vnet.ibm.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 Content-Length: 7433 Lines: 169 On Fri, Sep 15, 2017 at 05:59:21PM +0530, Nayna Jain wrote: > > > On 09/14/2017 04:40 AM, Jarkko Sakkinen wrote: > > On Wed, Sep 13, 2017 at 11:39:03AM -0700, Peter Huewe wrote: > > > > > > Am 12. September 2017 17:45:08 GMT-07:00 schrieb Jarkko Sakkinen : > > > > On Wed, Sep 06, 2017 at 08:56:36AM -0400, Nayna Jain wrote: > > > > > The TPM burstcount status indicates the number of bytes that can > > > > > be sent to the TPM without causing bus wait states. Effectively, > > > > > it is the number of empty bytes in the command FIFO. Further, > > > > > some TPMs have a static burstcount, when the value remains zero > > > > > until the entire FIFO is empty. > > > > > > > > > > This patch adds an optimization to check for burstcount only once. > > > > > And if it is valid, it writes all the bytes at once, permitting > > > > > wait states. The performance of a 34 byte extend on a TPM 1.2 with > > > > > an 8 byte burstcount improved from 41 msec to 14 msec. > > > > > > > > > > This functionality is enabled only by passing module > > > > > parameter ignore_burst_count=1. By default, this parameter > > > > > is disabled. > > > > > > > > > > After this change, performance on a TPM 1.2 with an 8 byte > > > > > burstcount for 1000 extends improved from ~41sec to ~14sec. > > > > > > > > > > Suggested-by: Ken Goldman in > > > > > conjunction with the TPM Device Driver work group. > > > > > Signed-off-by: Nayna Jain > > > > > Acked-by: Mimi Zohar > > > > > --- > > > > > Documentation/admin-guide/kernel-parameters.txt | 8 ++++++++ > > > > > drivers/char/tpm/tpm_tis_core.c | 24 > > > > +++++++++++++++++++++--- > > > > > 2 files changed, 29 insertions(+), 3 deletions(-) > > > > > > > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt > > > > b/Documentation/admin-guide/kernel-parameters.txt > > > > > index 4e303be83df6..3c59bb91e1ee 100644 > > > > > --- a/Documentation/admin-guide/kernel-parameters.txt > > > > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > > > > @@ -1465,6 +1465,14 @@ > > > > > mode generally follows that for the NaN encoding, > > > > > except where unsupported by hardware. > > > > > + ignore_burst_count [TPM_TIS_CORE] > > > > > + tpm_tis_core driver queries for the burstcount before > > > > > + every send call in a loop. However, it causes delay to > > > > > + the send command for TPMs with low burstcount value. > > > > > + Setting this value to 1, will make driver to query for > > > > > + burstcount only once in the loop to improve the > > > > > + performance. By default, its value is set to 0. > > > > > + > > > > > ignore_loglevel [KNL] > > > > > Ignore loglevel setting - this will print /all/ > > > > > kernel messages to the console. Useful for debugging. > > > > > diff --git a/drivers/char/tpm/tpm_tis_core.c > > > > b/drivers/char/tpm/tpm_tis_core.c > > > > > index 63bc6c3b949e..6b9bf4c4d434 100644 > > > > > --- a/drivers/char/tpm/tpm_tis_core.c > > > > > +++ b/drivers/char/tpm/tpm_tis_core.c > > > > > @@ -31,6 +31,11 @@ > > > > > #include "tpm.h" > > > > > #include "tpm_tis_core.h" > > > > > +static bool ignore_burst_count = false; > > > > > +module_param(ignore_burst_count, bool, 0444); > > > > > +MODULE_PARM_DESC(ignore_burst_count, > > > > > + "Ignore burstcount value while writing data"); > > > > > + > > > > > /* Before we attempt to access the TPM we must see that the valid > > > > bit is set. > > > > > * The specification says that this bit is 0 at reset and remains 0 > > > > until the > > > > > * 'TPM has gone through its self test and initialization and has > > > > established > > > > > @@ -256,6 +261,7 @@ static int tpm_tis_send_data(struct tpm_chip > > > > *chip, u8 *buf, size_t len) > > > > > { > > > > > struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev); > > > > > int rc, status, burstcnt; > > > > > + int sendcnt; > > > > > size_t count = 0; > > > > > bool itpm = priv->flags & TPM_TIS_ITPM_WORKAROUND; > > > > > @@ -271,19 +277,31 @@ static int tpm_tis_send_data(struct tpm_chip > > > > *chip, u8 *buf, size_t len) > > > > > } > > > > > while (count < len - 1) { > > > > > + > > > > > + /* > > > > > + * Get the initial burstcount to ensure TPM is ready to > > > > > + * accept data, even when waiting for burstcount is disabled. > > > > > + */ > > > > > burstcnt = get_burstcount(chip); > > > > > if (burstcnt < 0) { > > > > > dev_err(&chip->dev, "Unable to read burstcount\n"); > > > > > rc = burstcnt; > > > > > goto out_err; > > > > > } > > > > > - burstcnt = min_t(int, burstcnt, len - count - 1); > > > > > + > > > > > + if (ignore_burst_count) > > > > > + sendcnt = len - 1; > > > > > + else > > > > > + sendcnt = min_t(int, burstcnt, len - count - 1); > > > > > + > > > > > rc = tpm_tis_write_bytes(priv, TPM_DATA_FIFO(priv->locality), > > > > > - burstcnt, buf + count); > > > > > + sendcnt, buf + count); > > > > > if (rc < 0) > > > > > goto out_err; > > > > > - count += burstcnt; > > > > > + count += sendcnt; > > > > > + if (ignore_burst_count) > > > > > + continue; > > > > > if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c, > > > > > &priv->int_queue, false) < 0) { > > > > > -- > > > > > 2.13.3 > > > > > > > > > Makes sense to discuss whether to have the kernel command-line > > > > parameter or not before applying this. > > > > > > > > To fuel the discussion, alternative to this would be: > > > > > > > > 1. Have this always on i.e. no command-line parameter. > > > > 2. If someone yells, we add the command-line parameter later on. > > > > > > > According to what I've read in the tcg ddwg group this patch should > > > not cause problems on _sane_ tpms. > > > > > > I'm not 100%convinced that all tpms are sane all the time, but I think > > > we do not want yet another cmdline parameter. > > > > > > So if we want to pull it in (and ddwg does not see an issue, so yes) > > > it should be on by default, without a kernel parameter. > > > > > > If there is a kernel parameter, then it should only be one called > > > "failsafe" - which includes the force behavior and maybe the "broken" > > > tpm path. > > > > > > But I agree with Alex, every additonal code path reduces testing coverage. > > > > > > > > > We would be happy to test a "default on" patch. > > > > > > Peter > > > > > > > /Jarkko > > I'm starting to dilate to this direction. > > > > It is hard to believe that any such TPM would be in active use anywhere > > assuming that there exist a TPM where this causes issues. This combined > > to the assumption that you would run the latest mainline on it makes it > > a pretty insignificant scenario. > > It sounds like we are getting in direction to have this change by default. > Before removing the ignore_burst_count parameter, I will post a test version of this > patch which enables ignore_burst_count by default, for testing purposes only. > > Thanks Peter and Alex for testing. > > Thanks & Regards, > - Nayna I could apply it immediately after some testing to my next branch where it gets pulled to linux-next. There's still a lot of time before next pull request so many people would get exposed. If it cause problems, we reconsider. /Jarkko