Re: [Qemu-devel] [PATCH] PPC64: Fix timebase

[Andreas Färber]

Am 21.12.2009 um 11:15 schrieb Aurelien Jarno:

> On Mon, Dec 21, 2009 at 10:39:39AM +0100, Alexander Graf wrote:
> > On 21.12.2009, at 10:24, Aurelien Jarno wrote:
> >
> > > On Mon, Dec 21, 2009 at 01:22:12AM +0100, Alexander Graf wrote:
> > > > On PPC we have a 64-bit time base. Usually (PPC32) this is  
> > > > accessed using
> > > > two separate 32 bit SPR accesses to SPR_TBU and SPR_TBL.
> > > >
> > > > On PPC64 the SPR_TBL register acts as 64 bit though, so we get  
> > > > the full
> > > > 64 bits as return value. If we only take the lower ones, fine.  
> > > > But Linux
> > > > wants to see all 64 bits or it breaks.
> > >
> > > Good catch! However, I think this patch it's not fully complete  
> > > and can
> > > be improved a bit
> > > - it's probably better to return a target_ulong value from
> > > cpu_ppc_load_tbl() with an explicit cast here, so that we don't have
> > > an implicit cast from 64-bit to 32-bit on qemu-system-powerpc (GCC  
> > > may
> > > warn on that with some flags or in future versions).
> >
> > ppc.c is in hw, so I suspect it's in the target independent  
> > makefile part? Otherwise we should move all TB stuff to target-ppc.
>
> Correct.

No. Just like hw/ppc_newworld.c, it is target dependent and built from  
Makefile.target (obj-ppc-y).

Andreas

> then let's return uint64_t for cpu_ppc_load_tbl(), but do the
> explicit cast in the helper.
>
> --
> Aurelien Jarno                          GPG: 1024D/F1BCDB73
> address@hidden                 http://www.aurel32.net