Re: [Qemu-devel] [PATCH 1/8] virtio_get_byteswap: function for endian-ambivalent targets using virtio.

[Alexander Graf <agraf@suse.de>]

On 02/18/2014 01:38 PM, Greg Kurz wrote:
> From: Rusty Russell <rusty@rustcorp.com.au>
>
> virtio data structures are defined as "target endian", which assumes
> that's a fixed value.  In fact, that actually means it's
> platform-specific.
>
> The OASIS virtio 1.0 spec will fix this.  Meanwhile, create a hook for
> little endian ppc (and potentially ARM).  This is called at device
> reset time (which is done before any driver is loaded) since it
> may involve a system call to get the status when running under kvm.
>
> [ fixed checkpatch.pl error with the virtio_byteswap initialisation,
>    ldq_phys() API change, Greg Kurz <gkurz@linux.vnet.ibm.com> ]
> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> ---
>   hw/virtio/virtio.c                |    6 ++
>   include/hw/virtio/virtio-access.h |  132 +++++++++++++++++++++++++++++++++++++
>   include/hw/virtio/virtio.h        |    2 +
>   stubs/Makefile.objs               |    1
>   stubs/virtio_get_byteswap.c       |    6 ++
>   5 files changed, 147 insertions(+)
>   create mode 100644 include/hw/virtio/virtio-access.h
>   create mode 100644 stubs/virtio_get_byteswap.c
>
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index aeabf3a..4fd6ac2 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -19,6 +19,9 @@
>   #include "hw/virtio/virtio.h"
>   #include "qemu/atomic.h"
>   #include "hw/virtio/virtio-bus.h"
> +#include "hw/virtio/virtio-access.h"
> +
> +bool virtio_byteswap;

Could this be a virtio object property rather than a global? Imagine an 
AMP guest system with a BE and an LE system running in parallel 
accessing two separate virtio devices. With a single global that would 
break.


Alex