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Date: Thu, 12 Jun 2014 10:57:32 +0200
From: Alexander Graf <agraf@suse.de>
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Subject: Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent
	support to VirtIODevice
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To: Paolo Bonzini <pbonzini@redhat.com>, Greg Kurz <gkurz@linux.vnet.ibm.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Fam Zheng <famz@redhat.com>, Anthony Liguori <aliguori@amazon.com>, Juan Quintela <quintela@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>, Amit Shah <amit.shah@redhat.com>, =?ISO-8859-1?Q?Andreas_F=E4rber?= <afaerber@suse.de>


On 12.06.14 10:55, Paolo Bonzini wrote:
> Il 12/06/2014 09:43, Greg Kurz ha scritto:
>> Since we know that 0 < max_nr_ports < 32,  is it acceptable to guess
>> the correct endianness with a heuristic ?
>>
>> if (max_nr_ports > tswap32(s->config.max_nr_ports)) {
>>     max_nr_ports = bswap32(max_nr_ports);
>> }
>>
>> if (max_nr_ports > tswap32(s->config.max_nr_ports)) {
>>     return -EINVAL;
>> }
>
> Yes, I guess it is acceptable.  So first you should fix the code to 
> always serialize fields as big-endian, and then apply this little hack 
> and virtio_tswap on top of the previous change.

Why don't we just ignore those config fields? They won't change during 
the lifetime of the guest anyway - and configuration needs to be the 
same on source and dest to work.


Alex