Message-ID: <1362135005.3052.26.camel@hornet>
Subject: Re: [PATCH] virtio-spec: Define virtio-mmio registers as LE
From: Pawel Moll <pawel.moll@arm.com>
To: Marc Zyngier <Marc.Zyngier@arm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "virtualization@lists.linux-foundation.org" 
	<virtualization@lists.linux-foundation.org>
Date: Fri, 01 Mar 2013 10:50:05 +0000
In-Reply-To: <513085EA.8070007@arm.com>
References: <87wqubkalj.fsf@rustcorp.com.au>
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	 <513085EA.8070007@arm.com>
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On Fri, 2013-03-01 at 10:41 +0000, Marc Zyngier wrote:
> On 14/02/13 10:54, Pawel Moll wrote:
> > To solve the never-ending confusions between hosts and guests
> > of different endianess, define all virtio-mmio registers as LE.
> > 
> > This change should be safe at this stage, because no known
> > working mixed-endian system exists so there is virtually no
> > risk of breaking compatibility.
> > 
> > Signed-off-by: Pawel Moll <pawel.moll@arm.com>
>
> Shouldn't we exclude the config space? PCI defines it as guest-endian,
> and the above tends to indicate that it should be LE with MMIO.

The spec says: "Device-specific configuration space starts at an offset
0x100 and is accessed with byte alignment. Its meaning and size depends
on the device and the driver."

I would hope that "accessed with byte alignment" is enough of a clue in
this subject, but if you think otherwise I can add a sentence stating
this explicitly.

Having said that, Rusty was contemplating enforcing LE config space in
the new PCI layout...

Paweł


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