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Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability


From: Michael S. Tsirkin
Subject: Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability
Date: Mon, 6 Jul 2015 12:06:28 +0300

On Mon, Jul 06, 2015 at 10:46:31AM +0200, Paolo Bonzini wrote:
> 
> 
> 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.
> > 
> > Here's an example that's wrong: dp8393x. Typically it's accessing
> > memory for DMA, so there's no byteswap. Works fine.
> > 
> > But should device attempt to access another device memory,
> > it would break because MIPS target is BE.
> > 
> > Cc Hervé for confirmation.
> > 
> > I conclude that virtio is not so special in needing a variant
> > of address_space_rw that assumes host endian format for the data.
> 
> Why host endian and not device (in this case little) endian?
> 
> Paolo

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

-- 
MST



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