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

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Jun 02, 2016 at 06:04:37PM +0200, Greg Kurz wrote:
> On Wed, 1 Jun 2016 12:33:28 +1000
> David Gibson <david@gibson.dropbear.id.au> 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 <pbonzini@redhat.com>  
> > 
> > Should I take this through my tree?
> > 
> 
> That would be great !

Actually, that was a question for Paolo..


-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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