Re: [OpenBIOS] [PATCH v2] ppc: use rfid when running under a CPU from the 970 family.

[Alexander Graf]

> Am 22.06.2016 um 09:08 schrieb Cédric Le Goater :
> > On 06/22/2016 06:50 AM, Alexander Graf wrote:
> > > Am 21.06.2016 um 23:36 schrieb Cédric Le Goater :
> > >
> > > A recent attempt to restrict the use of rfi on 64bit cpus in qemu
> > > broke 32bit OpenBIOS when run under a 970.
> > >
> > > This patches memory to replace rfi instructions with rfid in the
> > > vector code.
> > >
> > > Signed-off-by: Cédric Le Goater 
> > > Suggested-by: Alexander Graf
> > >
> > > Tested on qemu.
> > >
> > > arch/ppc/qemu/ofmem.c |   24 ++++++++++++++++++++++++
> > > 1 file changed, 24 insertions(+)
> > > Index: openbios.git/arch/ppc/qemu/ofmem.c
> > >
> > > --- openbios.git.orig/arch/ppc/qemu/ofmem.c
> > > +++ openbios.git/arch/ppc/qemu/ofmem.c
> > > @@ -478,6 +478,26 @@ isi_exception(void)
> > >    hash_page(nip, phys, mode);
> > > }
> > >
> > > +/* When running on ppc64, we cannot use rfi anymore. Let's patch the
> > > vectors to use rfid instead.
> > > */
> > >
> > > +#define RFI     0x4c000064
> > > +#define RFID    0x4c000024
> > >
> > > +static void patch_rfi(char *from, uint32_t len)
> > > +{
> > > int i;
> > > for (i = 0; i < len; i += 4)  {
> > >    uint32_t* addr = (uint32_t *) (from + i);
> >
> > If you use a uint32* here you can just increment by 1 ...
> > >    if (*addr == RFI)
> > >        *addr = RFID;
> > > }
> > > flush_icache_range(from, from + len);
> > >
> > > +}
> > >
> > > +extern char __vectors[];
> > > +extern char __vectors_end[];
> >
> > And in fact you can just loop from vectors until ptr==vectors_end.
> >
> > uint32_t *ptr;
> >
> > for (ptr = __vectors; ptr != __vectors_end; ptr++)
>
> ah, we can not do that, we need to patch the memory and not the rom, so 
> [ 0,  __vectors_end - __vectors]

Aaah, I see. Then your version makes more sense.
> C.
> > > /************************************************************************/
> > > /*    init / cleanup                            */
> > > @@ -532,6 +552,10 @@ setup_mmu(unsigned long ramsize)
> > >
> > > memcpy((void *)get_rom_base(), (void *)OF_CODE_START, OF_CODE_SIZE);
> > > if (is_ppc64()) {
> > >    patch_rfi(0x0, (uint32_t) __vectors_end - (uint32_t) __vectors);

Please cast to uintptr_t instead though :)

Alex
> > > }
> >
> > Just fold all of this together. Make patch_rfi have no parameters and just call it unconditionally. Then check for ppc64 in there.
> >
> > Alex
> > > /* Enable MMU */
> > >
> > > mtmsr(mfmsr() | MSR_IR | MSR_DR);