linux-kernel - [PATCH v3 3/5] tpm: reduce polling delay in tpm_tis wait_for_tpm

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20171004102924.12355-4-nayna@linux.vnet.ibm.com>
Date:   Wed,  4 Oct 2017 06:29:22 -0400
From:   Nayna Jain <nayna@...ux.vnet.ibm.com>
To:     linux-integrity@...r.kernel.org
Cc:     zohar@...ux.vnet.ibm.com, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, peterhuewe@....de,
        jarkko.sakkinen@...ux.intel.com, tpmdd@...horst.net,
        jgunthorpe@...idianresearch.com, patrickc@...ibm.com,
        Nayna Jain <nayna@...ux.vnet.ibm.com>
Subject: [PATCH v3 3/5] tpm: reduce polling delay in tpm_tis wait_for_tpm_stat()

The existing wait_for_tpm_stat() polls for the chip status after
5msec sleep. As per TCG ddwg input, it is expected that tpm might
return status in few usec. So, reducing the delay in polling to
1msec.

After this change, performance on a TPM 1.2 with an 8 byte
burstcount for 1000 extends improved from ~14sec to ~10sec.

Signed-off-by: Nayna Jain <nayna@...ux.vnet.ibm.com>
---
 drivers/char/tpm/tpm_tis_core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 8da425e1783f..224842e06105 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -31,6 +31,8 @@
 #include "tpm.h"
 #include "tpm_tis_core.h"
 
+#define TPM_POLL_SLEEP	1
+
 static bool wait_for_tpm_stat_cond(struct tpm_chip *chip, u8 mask,
 					bool check_cancel, bool *canceled)
 {
@@ -82,7 +84,7 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
 		}
 	} else {
 		do {
-			tpm_msleep(TPM_TIMEOUT);
+			tpm_msleep(TPM_POLL_SLEEP);
 			status = chip->ops->status(chip);
 			if ((status & mask) == mask)
 				return 0;
-- 
2.13.3