linux-kernel - Re: [PATCH] vfio: Fix endianness handling for emulated BARs

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Message-ID: <1403646374.4587.178.camel@pasglop>
Date:	Wed, 25 Jun 2014 07:46:14 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Alexander Graf <agraf@...e.de>
Cc:	Alexey Kardashevskiy <aik@...abs.ru>,
	Alex Williamson <alex.williamson@...hat.com>,
	linuxppc-dev@...ts.ozlabs.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Nikunj A Dadhania <nikunj@...ux.vnet.ibm.com>
Subject: Re: [PATCH] vfio: Fix endianness handling for emulated BARs

On Tue, 2014-06-24 at 12:41 +0200, Alexander Graf wrote:
> Is there actually any difference in generated code with this patch 
> applied and without? I would hope that iowrite..() is inlined and 
> cancels out the cpu_to_le..() calls that are also inlined?

No, the former uses byteswapping asm, the compiler can't "cancel" it
out, but the overhead of the additional byteswap might not be
measurable.

Cheers,
Ben.


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