linux-kernel - Re: 2.6.37.1 s2disk regression (TPM)

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Message-ID: <4D628521.8000205@linux.vnet.ibm.com>
Date:	Mon, 21 Feb 2011 12:30:41 -0300
From:	Rajiv Andrade <srajiv@...ux.vnet.ibm.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Jiri Slaby <jirislaby@...il.com>, stefanb@...ux.vnet.ibm.com,
	linux-pm <linux-pm@...ts.linux-foundation.org>,
	stable@...nel.org,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>,
	debora@...ux.vnet.ibm.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	preining@...ic.at
Subject: Re: 2.6.37.1 s2disk regression (TPM)

On 02/20/2011 08:48 AM, Rafael J. Wysocki wrote:

> On Sunday, February 20, 2011, Rafael J. Wysocki wrote:
>> No, and the author and maintainer have not been responding.  If that contiunes,I'll simply ask Linus to revert it.
Sorry, but you sent the email this Friday, I didn't catch it in time and I wasn't working during the weekend.

> BTW, the first hunk from that commit in drivers/char/tpm/tpm.c seems to be
> completely broken:
>
> @@ -577,9 +577,11 @@ duration:
>          if (rc)
>                  return;
>
> -       if (be32_to_cpu(tpm_cmd.header.out.return_code)
> -           != 3 * sizeof(u32))
> +       if (be32_to_cpu(tpm_cmd.header.out.return_code) != 0 ||
> +           be32_to_cpu(tpm_cmd.header.out.length)
> +           != sizeof(tpm_cmd.header.out) + sizeof(u32) + 3 * sizeof(u32))
>                  return;
> +
>          duration_cap =&tpm_cmd.params.getcap_out.cap.duration;
>          chip->vendor.duration[TPM_SHORT] =
>              usecs_to_jiffies(be32_to_cpu(duration_cap->tpm_short));
>
> Namely, either the old code always returned as a result of the conditional
> being removed, or the new code will always return as a result of
> the (... != 0) check.  I wonder if there's supposed to be (... == 0) instead?
The previous code was checking the wrong field of the TPM returned buffer, probably
due an old commit that incorporated the tpm_cmd strucuture, it should check if the return code
is != 0, which if true, means that the command didn't succeed. The output length check should be
just a sanity check, so indeed the logical operator should be&&  instead. Although it should also be
fixed, I don't think this is the cause, since in case the timeout retrieval from the TPM fail,
the device driver falls back to default values, which has been working before this commit.

> [And why not to simply use 4*sizeof(u32) FWIW?]
I can't see why, I'll update it.

The failure for this specific board then sounds to be due the TPM returning inconsistent timeout values.
Norbert, can 'cat /sys/devices/pnp0/00\:0*/timeouts' and send the output?

Rajiv


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