Re: [RFC PATCH 0/4] vhost_net: support for cross endian guests

[Cedric Le Goater <clg@fr.ibm.com>]

On 11/03/2014 05:23 PM, Michael S. Tsirkin wrote:
> On Wed, Oct 29, 2014 at 09:38:41AM +0100, Cédric Le Goater wrote:
>> This patchset adds a VHOST_VRING_F_BYTESWAP flag to inform the host 
>> to byteswap data of the vring when the guest and the host have a 
>> different endian order. The flag is stored at initialization in an 
>> attribute of the virtio queues. It is then used to byteswap, or not, 
>> the vring indexes and descriptors shared with the guest OS.
>>
>> The last patch adds the byteswapping of the virtio_net header as it 
>> is done in qemu.
> 
> Hi Cedric,
> 
> Thanks for submitting this.
> One general problem with this approach, is that
> it adds overhead e.g. for x86 on x86 unconditionally.

Yes but it should be possible to #ifdef most of the routines to
make them transparent for x86. 

> I will in a couple of days post a patch adding virtio 1.0
> support for vhost.
> 
> This will serve as a better basis for cross-endian support in
> vhost, on top.

ok. I will rework the patchset on top of it then.

> I'll try to remember to Cc you.

Thanks.

C.


 
>> The patches apply on linux-3.18-rc2 and the tests were done on PowerPC 
>> using the following hosts :
>>  
>>    	 fedora21/ppc64, utopic/ppc64le  
>>
>> with various guests : 
>>
>>    	 trusty/ppc64le, utopic/ppc64le, debian/ppc64le, 
>>    	 rhel6.5/ppc64, fedora21/ppc64, debian/ppc64
>>
>> Regressions tests for x86_64 were done a debian host using rhel6.6, 
>> fedora20 and debian guests.
>> 	
>>
>> Cédric Le Goater (4):
>>   vhost: add VHOST_VRING_F_BYTESWAP flag
>>   vhost: add byteswap routines
>>   vhost: byteswap virtqueue attributes
>>   vhost_net: byteswap virtio_net header
>>
>>  drivers/vhost/net.c        |   39 +++++++++---
>>  drivers/vhost/vhost.c      |  150 ++++++++++++++++++++++++++++++++++++++++----
>>  drivers/vhost/vhost.h      |    1 +
>>  include/uapi/linux/vhost.h |    3 +
>>  4 files changed, 171 insertions(+), 22 deletions(-)
>>
>> -- 
>> 1.7.10.4
>