Subject: Re: [Alacrityvm-devel] [PATCH v3 3/6] vbus: add a "vbus-proxy" bus model for vbus_driver objects

From: Avi Kivity <[email-masked]>
Date: Thu, 20 Aug 2009 13:08:59 +0300

On 08/20/2009 12:57 PM, Stefan Hajnoczi wrote:
> Cross-platform virtio works when endianness is known in advance.  For
> a hypervisor and a guest:
> 1. virtio-pci I/O registers use PCI endianness
> 2. vring uses guest endianness (hypervisor must byteswap)
> 3. guest memory buffers use guest endianness (hypervisor must byteswap)
>
> I know of no existing way when endianness is not known in advance.
> Perhaps a transport bit could be added to mark the endianness of the
> guest/driver side.  This can be negotiated because virtio-pci has a
> known endianness.  After negotiation, the host knows whether or not
> byteswapping is necessary for structures in guest memory.
>
>    

Some processors are capable of switching their gender at runtime, so you 
cannot tell the guest endianness in advance.

-- 
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