Re: [PATCH v4 1/2] vTPM: support little endian guests

From: "Hon Ching(Vicky) Lo" <honclo@linux.vnet.ibm.com>
To: "Peter Hüwe" <PeterHuewe@gmx.de>
Cc: tpmdd-devel@lists.sourceforge.net,
	Ashley Lai <ashley@ashleylai.com>,
	Vicky Lo <honclo2014@gmail.com>,
	linux-kernel@vger.kernel.org,
	Joy Latten <jmlatten@linux.vnet.ibm.com>
Subject: Re: [PATCH v4 1/2] vTPM: support little endian guests
Date: Thu, 16 Jul 2015 13:54:15 -0400	[thread overview]
Message-ID: <1437069255.29298.5.camel@vtpm2014.ibm.com> (raw)
In-Reply-To: <201507132308.00824.PeterHuewe@gmx.de>

Hi Peter,

On Mon, 2015-07-13 at 23:08 +0200, Peter Hüwe wrote:
> Hi Vicky,
> 
> sorry for the late reply
> 
> 
> > This patch makes the code endianness independent. We defined a
> > macro do_endian_conversion to apply endianness to raw integers
> > in the event entries so that they will be displayed properly.
> > tpm_binary_bios_measurements_show() is modified for the display.
> > 
> > Signed-off-by: Hon Ching(Vicky) Lo <honclo@linux.vnet.ibm.com>
> > Signed-off-by: Joy Latten <jmlatten@linux.vnet.ibm.com>
> 
> > b/drivers/char/tpm/tpm_eventlog.h index e7da086..267bfbd 100644
> > --- a/drivers/char/tpm/tpm_eventlog.h
> > +++ b/drivers/char/tpm/tpm_eventlog.h
> > @@ -6,6 +6,12 @@
> >  #define MAX_TEXT_EVENT		1000	/* Max event string length */
> >  #define ACPI_TCPA_SIG		"TCPA"	/* 0x41504354 /'TCPA' */
> > 
> > +#ifdef CONFIG_PPC64
> > +#define do_endian_conversion(x) be32_to_cpu(x)
> > +#else
> > +#define do_endian_conversion(x) x
> > +#endif
> 
> 
> Why is this macro needed?
> shouldn't the be32_to_cpu macro already do correct thing?
> Or am I missing something here?
> 
> 
> Thanks,
> Peter
> 
The macro is defined to not do the conversion in the architecture
that does not need it.

Regards,
Vicky