linux-kernel - RE: [PATCH v2 1/6] powerpc/perf: Define big-endian version of perf_mem_data

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6DCFE78C84@AcuExch.aculab.com>
Date:   Mon, 6 Mar 2017 14:59:07 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Peter Zijlstra' <peterz@...radead.org>,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
CC:     Wang Nan <wangnan0@...wei.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "Stephane Eranian" <eranian@...gle.com>,
        Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: RE: [PATCH v2 1/6] powerpc/perf: Define big-endian version of
 perf_mem_data_src

From: Peter Zijlstra
> Sent: 06 March 2017 11:22
> To: Madhavan Srinivasan
> Cc: Wang Nan; Alexander Shishkin; linux-kernel@...r.kernel.org; Arnaldo Carvalho de Melo; Alexei
> Starovoitov; Ingo Molnar; Stephane Eranian; Sukadev Bhattiprolu; linuxppc-dev@...ts.ozlabs.org
> Subject: Re: [PATCH v2 1/6] powerpc/perf: Define big-endian version of perf_mem_data_src
> 
> On Mon, Mar 06, 2017 at 04:13:08PM +0530, Madhavan Srinivasan wrote:
> > From: Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
> >
> > perf_mem_data_src is an union that is initialized via the ->val field
> > and accessed via the bitmap fields. For this to work on big endian
> > platforms, we also need a big-endian represenation of perf_mem_data_src.
> 
> Doesn't this break interpreting the data on a different endian machine?

Best to avoid bitfields if you ever care about the bit order.

	David