From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Nayna Jain <nayna@linux.vnet.ibm.com>
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
Date: Tue, 8 Aug 2017 22:07:39 +0300 [thread overview]
Message-ID: <20170808190739.bpmet2jqni3lt6pa@linux.intel.com> (raw)
In-Reply-To: <20170807114632.1339-1-nayna@linux.vnet.ibm.com>
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 <kgold@linux.vnet.ibm.com> in
> conjunction with the TPM Device Driver work group.
> Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
> Acked-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
> ---
> 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
prev parent reply other threads:[~2017-08-08 19:07 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-07 11:46 [PATCH] tpm: improve tpm_tis send() performance by ignoring burstcount Nayna Jain
2017-08-07 11:52 ` Peter Huewe
2017-08-07 14:25 ` Nayna
2017-08-08 21:50 ` Jarkko Sakkinen
2017-08-08 19:11 ` Jarkko Sakkinen
2017-08-09 20:23 ` [tpmdd-devel] " Ken Goldman
2017-08-09 20:43 ` Aw: " Peter Huewe
2017-08-11 21:54 ` Ken Goldman
[not found] ` <20170814101046.5hqrkaqmfvl7ugwj@linux.intel.com>
2017-08-16 19:51 ` Ken Goldman
2017-08-09 20:25 ` Ken Goldman
2017-08-09 21:00 ` Aw: " Peter Huewe
2017-08-11 11:14 ` Jarkko Sakkinen
2017-08-11 15:30 ` Mimi Zohar
2017-08-14 10:51 ` Jarkko Sakkinen
2017-08-14 10:56 ` Jarkko Sakkinen
2017-08-14 12:03 ` Mimi Zohar
2017-08-15 6:08 ` Jarkko Sakkinen
2017-08-14 12:12 ` Mimi Zohar
2017-08-15 6:09 ` Jarkko Sakkinen
2017-08-11 21:32 ` Aw: " Ken Goldman
2017-08-13 23:53 ` msuchanek
2017-08-15 22:02 ` Ken Goldman
2017-08-16 10:24 ` Michal Suchánek
2017-08-11 21:42 ` [Linux-ima-devel] " Ken Goldman
2017-08-08 19:07 ` Jarkko Sakkinen [this message]
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