linux-kernel - Re: [tpmdd-devel] [PATCH v3] drivers/tpm: add xen tpmfront interface

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Message-Id: <201306050014.29162.PeterHuewe@gmx.de>
Date:	Wed, 5 Jun 2013 00:14:28 +0200
From:	Peter Hüwe <PeterHuewe@....de>
To:	tpmdd-devel@...ts.sourceforge.net
Cc:	Daniel De Graaf <dgdegra@...ho.nsa.gov>,
	linux-kernel@...r.kernel.org, leosilva@...ux.vnet.ibm.com,
	shpedoikal@...il.com, konrad.wilk@...cle.com,
	xen-devel@...ts.xen.org, mail@...jiv.net, adlai@...ux.vnet.ibm.com,
	tpmdd@...rix.com
Subject: Re: [tpmdd-devel] [PATCH v3] drivers/tpm: add xen tpmfront interface

Hi Daniel,

thanks for this v3.
It's really nice to see the progress and I really like that 
sparse/smatch/clang/coccicheck do not complain at all - nice job!

Konrad already did an excellent job at reviewing the driver (thanks for that), 
and all previously pointed out issues are fixed.

Unfortunately I haven't had the opportunity to test it yet, but 
the driver looks clean from the TPM perspective.


However I do have some minor comments from a general perspective - see below.


>From the TPM point of view I'd say it is fine.
(I'm currently _not_ the (official) maintainer of the tpm subsystem but at least 
take care of the incoming stuff as an interim)


So if the comments are addressed you can add:
Acked-by: Peter Huewe <peterhuewe@....de>
Reviewed-by: Peter Huewe <peterhuewe@....de>

@Konrad: I can stage the driver and push it to James or you can take it.
As it lives in drivers/tpm maybe it should go through the tpm (interim ;) 
maintainer and james' tree.


So here are my comments:

Am Dienstag, 28. Mai 2013, 17:40:32 schrieb Daniel De Graaf:
> This is a complete rewrite of the Xen TPM frontend driver, taking
> advantage of a simplified frontend/backend interface and adding support
> for cancellation and timeouts.  The backend for this driver is provided
> by a vTPM stub domain using the interface in Xen 4.3.
> 
> Signed-off-by: Daniel De Graaf <dgdegra@...ho.nsa.gov>
> Acked-by: Matthew Fioravante <matthew.fioravante@...apl.edu>

> diff --git a/Documentation/xen-tpmfront.txt
> b/Documentation/xen-tpmfront.txt new file mode 100644
> index 0000000..8a61d6f
> --- /dev/null
> +++ b/Documentation/xen-tpmfront.txt
> @@ -0,0 +1,116 @@
> +Copyright (c) 2010-2012 United States Government, as represented by
> +the Secretary of Defense.  All rights reserved.

I'm not 100% sure if this can stay this way, as it doesn't permit any changes 
to the documentation itself.


> + * Linux DomU: The Linux based guest that wants to use a vTPM. There many
> be +	       more than one of these.
-* Linux DomU: The Linux based guest that wants to use a vTPM. There many
+* Linux DomU: The Linux based guest that wants to use a vTPM. There may
Just a minor typo


> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> index dbfd564..205ed35 100644
> --- a/drivers/char/tpm/Kconfig
> +++ b/drivers/char/tpm/Kconfig
> @@ -91,4 +91,15 @@ config TCG_ST33_I2C
>          To compile this driver as a module, choose M here; the module will
> be called tpm_stm_st33_i2c.
> 
> +config TCG_XEN
Maybe TCG_XEN_TPM would be better, but TCG_XEN is okay for me.


> +static int vtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
> +{
> +	struct tpm_private *priv = TPM_VPRIV(chip);
> +	struct vtpm_shared_page *shr = priv->shr;
> +	unsigned int offset = shr_data_offset(shr);
> +
> +	u32 ordinal;
> +	unsigned long duration;
> +
> +	if (offset > PAGE_SIZE)
> +		return -EIO;
Maybe -EINVAL?
> +
> +	if (offset + count > PAGE_SIZE)
> +		return -EIO;
Maybe -EINVAL?
> +


> +/*************************************************************************
> ***** + * tpmif.h
> + *
> + * TPM I/O interface for Xen guest OSes, v2
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> copy + * of this software and associated documentation files (the
> "Software"), to + * deal in the Software without restriction, including
> without limitation the + * rights to use, copy, modify, merge, publish,
> distribute, sublicense, and/or + * sell copies of the Software, and to
> permit persons to whom the Software is + * furnished to do so, subject to
> the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included
> in + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
> OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
> IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
> CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
> TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE
> SOFTWARE OR THE USE OR OTHER + * DEALINGS IN THE SOFTWARE.
> + *
> + */

Also not sure if this license is correct/compliant with the kernel as it 
indicates no clear license to me.

Peter
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