Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752261AbdHHTHp (ORCPT ); Tue, 8 Aug 2017 15:07:45 -0400 Received: from mga04.intel.com ([192.55.52.120]:43721 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752070AbdHHTHn (ORCPT ); Tue, 8 Aug 2017 15:07:43 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,344,1498546800"; d="scan'208";a="1203445680" Date: Tue, 8 Aug 2017 22:07:39 +0300 From: Jarkko Sakkinen To: Nayna Jain Cc: tpmdd-devel@lists.sourceforge.net, peterhuewe@gmx.de, 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] tpm: improve tpm_tis send() performance by ignoring burstcount Message-ID: <20170808190739.bpmet2jqni3lt6pa@linux.intel.com> References: <20170807114632.1339-1-nayna@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170807114632.1339-1-nayna@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: 3256 Lines: 99 On Mon, Aug 07, 2017 at 07:46:32AM -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 ignores burstcount, permitting wait states, and thus > writes the command as fast as the TPM can accept the bytes. > The performance of a 34 byte extend on a TPM 1.2 improved from > 52 msec to 11 msec. > > Suggested-by: Ken Goldman in > conjunction with the TPM Device Driver work group. > Signed-off-by: Nayna Jain > Acked-by: Mimi Zohar > --- > drivers/char/tpm/tpm_tis_core.c | 45 ++--------------------------------------- > 1 file changed, 2 insertions(+), 43 deletions(-) > > diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c > index b617b2eeb080..478cbc0f61c3 100644 > --- a/drivers/char/tpm/tpm_tis_core.c > +++ b/drivers/char/tpm/tpm_tis_core.c > @@ -255,9 +255,7 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count) > 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; > - size_t count = 0; > - bool itpm = priv->flags & TPM_TIS_ITPM_WORKAROUND; > + int rc, status; As you anyway edit that line you could turn this as: int rc; int status; > status = tpm_tis_status(chip); > if ((status & TPM_STS_COMMAND_READY) == 0) { > @@ -270,49 +268,10 @@ static int tpm_tis_send_data(struct tpm_chip *chip, u8 *buf, size_t len) > } > } > > - while (count < len - 1) { > - 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); > - rc = tpm_tis_write_bytes(priv, TPM_DATA_FIFO(priv->locality), > - burstcnt, buf + count); > - if (rc < 0) > - goto out_err; > - > - count += burstcnt; > - > - if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c, > - &priv->int_queue, false) < 0) { > - rc = -ETIME; > - goto out_err; > - } > - status = tpm_tis_status(chip); > - if (!itpm && (status & TPM_STS_DATA_EXPECT) == 0) { > - rc = -EIO; > - goto out_err; > - } > - } > - > - /* write last byte */ > - rc = tpm_tis_write8(priv, TPM_DATA_FIFO(priv->locality), buf[count]); > + rc = tpm_tis_write_bytes(priv, TPM_DATA_FIFO(priv->locality), len, buf); > if (rc < 0) > goto out_err; > > - if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c, > - &priv->int_queue, false) < 0) { > - rc = -ETIME; > - goto out_err; > - } > - status = tpm_tis_status(chip); > - if (!itpm && (status & TPM_STS_DATA_EXPECT) != 0) { > - rc = -EIO; > - goto out_err; > - } > - > return 0; > > out_err: > -- > 2.13.3 Here's an open question that I do not know the answer: can ignoring burst count cause hardware issues in the field? The commit message does not sort it out so I don't really feel safe merging this commit. /Jarkko