From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal =?UTF-8?B?U3VjaMOhbmVr?= Subject: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send() performance by ignoring burstcount Date: Wed, 16 Aug 2017 12:24:23 +0200 Message-ID: <20170816122423.315817c7@kitsune.suse.cz> References: <20170807114632.1339-1-nayna@linux.vnet.ibm.com> <20170808191145.kggmoczd5laiccrn@linux.intel.com> <9cb350b6-32fd-529e-eb31-6800339cddb2@linux.vnet.ibm.com> <20170814015359.30177c87@naga> <869cc1b1-0836-a53b-31d7-9fec50d8cc52@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <869cc1b1-0836-a53b-31d7-9fec50d8cc52@linux.vnet.ibm.com> Sender: owner-linux-security-module@vger.kernel.org To: Ken Goldman Cc: linux-ima-devel@lists.sourceforge.net, linux-security-module@vger.kernel.org, tpmdd-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org List-Id: tpmdd-devel@lists.sourceforge.net On Tue, 15 Aug 2017 18:02:57 -0400 Ken Goldman wrote: > On 8/13/2017 7:53 PM, msuchanek wrote: > > About 500 out of 700 mainboards sold today has a PS/2 port which is > > probably due to prevalence of legacy devices and usbhid limitations. > > > > Similarily many boards have serial and parallel hardware ports. > > > > In all diagrams detailed enough to show these ports I have seen them > > attached to the LPC bus. > > Do these boards have a TPM? Remember that the TPM requires special > LPC bus cycles. Out of nearly 700 boards over 500 have PS/2 connector and over 400 have TPM slot (which is subset of the PS/2 enabled boards). Some more possibly have on-board TPM chip. > > Even if so, the TPM LPC bus wait states are less than a usec. My > thought is that it's unlikely that any device (serial port, mouse, > keyboard, printer) will be adversely affected. Yes, in theory this is negligible. So unless there is a possibility these wait states chain or the device otherwise takes over the bus for extended period of time this should be fine. Thanks Michal