Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751422AbdIMXKU (ORCPT ); Wed, 13 Sep 2017 19:10:20 -0400 Received: from mga06.intel.com ([134.134.136.31]:49201 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751125AbdIMXKR (ORCPT ); Wed, 13 Sep 2017 19:10:17 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.42,390,1500966000"; d="scan'208";a="1194836353" Date: Wed, 13 Sep 2017 16:10:07 -0700 From: Jarkko Sakkinen To: Peter Huewe Cc: Nayna Jain , 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: <20170913231007.22yb57hlx45aznt6@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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: 6071 Lines: 160 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. /Jarkko