Re: [Qemu-arm] [PATCH] virtio: move bi-endian target support to a single location

[Greg Kurz]

On Fri, 3 Jun 2016 11:16:04 +1000
David Gibson <address@hidden> wrote:

> On Thu, Jun 02, 2016 at 06:04:37PM +0200, Greg Kurz wrote:
> > On Wed, 1 Jun 2016 12:33:28 +1000
> > David Gibson <address@hidden> wrote:
> >   
> > > On Tue, May 31, 2016 at 03:15:21PM +0200, Paolo Bonzini wrote:  
> > > > 
> > > > 
> > > > On 31/05/2016 15:10, Greg Kurz wrote:    
> > > > >>> > > +#if defined(TARGET_PPC64) || defined(TARGET_ARM)
> > > > >>> > > +#define LEGACY_VIRTIO_IS_BIENDIAN 1
> > > > >>> > > +#endif      
> > > > >> > 
> > > > >> > These will only be correct if something else includes cpu.h.  
> > > > >> > Instead of    
> > > > > Unless I missed something, the TARGET_* macros come from the generated
> > > > > config-target.h header, which is in turn included by qemu/osdep.h and
> > > > > thus included by most of the code.    
> > > > 
> > > > You're right.  Problems _could_ happen if virtio-access.h is included in
> > > > a file compiled without -DNEED_CPU_H (i.e. with common-obj-y instead of
> > > > obj-y) but include/exec/poison.h should take care of that.
> > > >     
> > > > >> > defining this, you should add
> > > > >> > 
> > > > >> > #include "cpu.h"
> > > > >> > 
> > > > >> > at the top of include/hw/virtio-access.h and leave the definitions 
> > > > >> > in
> > > > >> > target-*/cpu.h.
> > > > >> >     
> > > > > All this bi-endian stuff is really an old-virtio-only thing... it is
> > > > > only to be used by virtio_access_is_big_endian(). The fact that it
> > > > > broke silently with your cleanup series is yet another proof that
> > > > > this workaround is fragile.    
> > > > 
> > > > It is not fragile actually.  cpu.h doesn't exist in common-obj-y, so the
> > > > TARGET_IS_BIENDIAN define can be safely taken from cpu.h.
> > > > 
> > > > Anyway because of poison.h your solution isn't fragile either, so
> > > > 
> > > > Reviewed-by: Paolo Bonzini <address@hidden>    
> > > 
> > > Should I take this through my tree?
> > >   
> > 
> > That would be great !  
> 
> Actually, that was a question for Paolo..
> 
> 

Sure, I was just expressing my interest for this possibility... :)