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

[Cédric Le Goater]

On 06/22/2016 06:50 AM, Alexander Graf wrote:
> 
> 
>> Am 21.06.2016 um 23:36 schrieb Cédric Le Goater <clg at kaod.org>:
>>
>> 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 <clg at kaod.org>
>> Suggested-by: Alexander Graf <agraf at suse.de>
>> ---
>>
>> 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 ...

yes. I tried a couple of versions and that was the most friendly for the
flush_icache_range.

 
>> +        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++)
> 
>>
>> /************************************************************************/
>> /*    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);
>> +    }
> 
> Just fold all of this together. Make patch_rfi have no parameters and just call it unconditionally. Then check for ppc64 in there.

ok. v3 on the way.

Thanks, 

C. 

> Alex
> 
>> +
>>     /* Enable MMU */
>>
>>     mtmsr(mfmsr() | MSR_IR | MSR_DR);
>