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Date: Mon, 6 Jul 2015 12:06:28 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: peter.maydell@linaro.org, hpoussin@reactos.org, qemu-devel@nongnu.org

On Mon, Jul 06, 2015 at 10:46:31AM +0200, Paolo Bonzini wrote:
>=20
>=20
> On 06/07/2015 10:33, Michael S. Tsirkin wrote:
> > Also, by luck, some values work the same whatever the endian-ness.
> > E.g. dma_memory_set fills the buffer with a given pattern, so
> > nothing changes if you byte-swap it.
> >=20
> > Here's an example that's wrong: dp8393x. Typically it's accessing
> > memory for DMA, so there's no byteswap. Works fine.
> >=20
> > But should device attempt to access another device memory,
> > it would break because MIPS target is BE.
> >=20
> > Cc Herv=E9 for confirmation.
> >=20
> > I conclude that virtio is not so special in needing a variant
> > of address_space_rw that assumes host endian format for the data.
>=20
> Why host endian and not device (in this case little) endian?
>=20
> Paolo

It's the endian of the originator of the transaction.
And emulated device code is all compiled in host endian-ness.

--=20
MST