linux-kernel - RE: [PATCH 3/5 V2] tpm2: add longer timeouts for creation commands.

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Message-ID: <5B8DA87D05A7694D9FA63FD143655C1B9422F4C1@hasmsx108.ger.corp.intel.com>
Date:   Tue, 6 Mar 2018 15:19:23 +0000
From:   "Winkler, Tomas" <tomas.winkler@...el.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Jason Gunthorpe <jgg@...pe.ca>
CC:     "Usyskin, Alexander" <alexander.usyskin@...el.com>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 3/5 V2] tpm2: add longer timeouts for creation commands.

> On Tue, 2018-03-06 at 11:25 +0200, Tomas Winkler wrote:
> > TPM2_CC_Create(0x153) and TPM2_CC_CreatePrimary (0x131) involve
> > generation of crypto keys which can be a computationally intensive task.
> > The timeout is set to 3min.
> > Rather than increasing default timeout a new constant is added, to not
> > stall for too long on regular commands failures.
> >
> > Signed-off-by: Tomas Winkler <tomas.winkler@...el.com>
> 
> Why are you radically chaging the default timeout? The commit message
> does not tell anything about that change.
>
Let me, recheck but it should be same value just converted to msecs.
 
> Why couldn't we just have two timeouts: one default and one long that
> would be at least as long as the longest timeout defined in the spec?

I've tried to explain it in the commit message but apparently has failed. 

We have a default or undefined which should be the same as it was unless I did some silly mistake in conversion to msecs (will check), ass all others are in msecs.
It was 2 min = 2 * 60 * HZ (in jiffies) which would be msecs_to_jiffies(2 * 60 * 1000 = 120000) 
TPM2_DURATION_DEFAULT   = 120000

Then we have a new one which is 3 min just for key generation (Prime number generation is heavy liffting) 

> Then we would not have to ever update LAST_CC constant, we could actually
> remove it completely.

I believe I've removed it next patch, I didn’t want do too much in this one.

Thanks
Tomas