From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marc Zyngier <marc.zyngier@arm.com>
Subject: Re: [PATCH 0/3] virtio-mmio: handle BE guests on LE hosts
Date: Mon, 14 Oct 2013 16:12:17 +0100
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Cc: Alexander Graf <agraf@suse.de>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	"kvm@vger.kernel.org mailing list" <kvm@vger.kernel.org>,
	Pawel Moll <Pawel.Moll@arm.com>,
	"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
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To: Paolo Bonzini <pbonzini@redhat.com>
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On 14/10/13 15:56, Paolo Bonzini wrote:
> Il 14/10/2013 16:52, Marc Zyngier ha scritto:
>>>> Sure. And I imagine this traps back into the kernel to read some
>>>> register and find out what the endianness of the accessing CPU is?
>>>
>>> Not yet. To be exact, it does the below today. But all virtio device
>>> emulation is 100% guest endianness unaware. This helper is the only
>>> piece of code where it gets any idea what endianness the guest has. So
>>> by checking for references to it in the code you know where endianness
>>> is an issue. And that's only in the config space.
>>
>> Only config space? How do you deal with virtio ring descriptors, for
>> example?
> 
> They also use guest endianness, but do not use virtio_is_big_endian()
> (yet?) so Alex missed them.

Yeah, I thought as much. There is a whole bunch of things that need byte
swapping, both at the virtio level itself, and at the device level as well.

Grep-ing for __u{16,32,64} through include/uapi/linux/virtio* shows the
extent of the disaster.

	M.
-- 
Jazz is not dead. It just smells funny...