linux-kernel - Re: Getting weird TPM error after rebasing my tree to security/next-general

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Date:   Tue, 22 Jan 2019 15:29:28 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...pe.ca>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     James Bottomley <James.Bottomley@...senPartnership.com>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Getting weird TPM error after rebasing my tree to
 security/next-general

On Mon, Jan 21, 2019 at 07:58:36PM -0700, Jason Gunthorpe wrote:
> On Tue, Jan 22, 2019 at 03:02:18AM +0200, Jarkko Sakkinen wrote:
> > On Sun, Jan 20, 2019 at 06:04:13PM +0200, Jarkko Sakkinen wrote:
> > > On Fri, Jan 18, 2019 at 02:09:18PM -0800, James Bottomley wrote:
> > > > On Fri, 2019-01-18 at 16:25 +0200, Jarkko Sakkinen wrote:
> > > > > I get this on a Geminilake NUC after rebasing my maintainer trees:
> > > > > 
> > > > > tpm tpm0: A TPM error (-1) occurred attempting the self test
> > > > > 
> > > > > I checked the latest commit ID from drivers/char/tpm to make sure
> > > > > that I did not put anything broken to my last PR [1]. It works
> > > > > without issues.
> > > > > 
> > > > > In addition [2] gives me an empty diff.
> > > > > 
> > > > > Something outside of the TPM driver must have happened that breaks
> > > > > the driver. Any ideas?
> > > > > 
> > > > > [1] commit 9488585b21bef0df1217e510c7134905d1d376a7
> > > > > [2] git diff 9488585b21bef0df1217e510c7134905d1d376a7 master
> > > > > drivers/char/tpm/
> > > > 
> > > > I'm afraid you're going to have to bisect to find the offending in-
> > > > kernel commit, which is going to be painful since it seems to depend on
> > > > physical hardware.  My first instinct is that we're getting a zero
> > > > length read somewhere, but I still can't see anything in the merge
> > > > window that would cause that behaviour.
> > > 
> > > Yeah, I've started to bisect it (still 9 rounds to go).
> > 
> > Fails on commit 170d13ca3a2fdaaa0283399247631b76b441cca2. Still works on
> > preceding commit a959dc88f9c8900296ccf13e2f3e1cbc555a8917.
> 
> This changes the IO access pattern in memcpy_to/fromio.. Presumably
> CRB HW doesn't like the new 4 byte move? Swap each one in crb to
> memcpy to confirm..
> 
> If the HW requires particular access patterns you can't use
> memcpy_to/fromio

Did not have time to look at the commit at all but your deduction
is correct. I know it without testing.

Memory controller will feed 1's on unaligned read from IO memory,
and as we can see from the TPM header, this change causes two of
those:

struct tpm_output_header {
	__be16	tag;
	__be32	length;
	__be32	return_code;
} __packed;

/Jarkko