From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nayna Jain Subject: Re: [PATCH v2 1/4] tpm: ignore burstcount to improve tpm_tis send() performance. Date: Fri, 15 Sep 2017 17:59:21 +0530 Message-ID: <3c83ac72-59cc-f6c8-26ca-b7f8a8887d39@linux.vnet.ibm.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> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20170913231007.22yb57hlx45aznt6@linux.intel.com> Content-Language: en-US Sender: owner-linux-security-module@vger.kernel.org To: Jarkko Sakkinen , Peter Huewe Cc: 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 List-Id: tpmdd-devel@lists.sourceforge.net 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 > > /Jarkko >