[PATCH] powerpc/85xx: Fix math emulation exception

[Christophe Leroy]

Le 10/10/2023 à 12:45, Michael Ellerman a écrit :
> Christophe Leroy <christophe.leroy at csgroup.eu> writes:
>> Booting mpc85xx_defconfig kernel on QEMU leads to:
> 
> What machine/CPU model are you using for that?

If I remember correctly, it was machine mpc8544ds.

Christophe

> 
> I tried ppce500/e500 and that is working OK for me, ie. boots to
> userspace and I see math instructions being emulated via the emulated
> stats.
> 
> cheers
> 
>> Bad trap at PC: fe9bab0, SR: 2d000, vector=800
>> awk[82]: unhandled trap (5) at 0 nip fe9bab0 lr fe9e01c code 5 in libc-2.27.so[fe5a000+17a000]
>> awk[82]: code: 3aa00000 3a800010 4bffe03c 9421fff0 7ca62b78 38a00000 93c10008 83c10008
>> awk[82]: code: 38210010 4bffdec8 9421ffc0 7c0802a6 <fc00048e> d8010008 4815190d 93810030
>> Trace/breakpoint trap
>> WARNING: no useful console
>>
>> This is because allthough CONFIG_MATH_EMULATION is selected,
>> Exception 800 calls unknown_exception().
>>
>> Call emulation_assist_interrupt() instead.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy at csgroup.eu>
>> ---
>>   arch/powerpc/kernel/head_85xx.S | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/kernel/head_85xx.S b/arch/powerpc/kernel/head_85xx.S
>> index 97e9ea0c7297..0f1641a31250 100644
>> --- a/arch/powerpc/kernel/head_85xx.S
>> +++ b/arch/powerpc/kernel/head_85xx.S
>> @@ -395,7 +395,7 @@ interrupt_base:
>>   #ifdef CONFIG_PPC_FPU
>>   	FP_UNAVAILABLE_EXCEPTION
>>   #else
>> -	EXCEPTION(0x0800, FP_UNAVAIL, FloatingPointUnavailable, unknown_exception)
>> +	EXCEPTION(0x0800, FP_UNAVAIL, FloatingPointUnavailable, emulation_assist_interrupt)
>>   #endif
>>   
>>   	/* System Call Interrupt */
>> -- 
>> 2.41.0