Re: [PATCH] powerpc/32: Add missing context synchronisation with CONFIG_VMAP_STACK

[Michael Ellerman]

Christophe Leroy <christophe.leroy@xxxxxx> writes:
> Michael Ellerman <mpe@xxxxxxxxxxxxxx> a ÃcritÂ:
>> Christophe Leroy <christophe.leroy@xxxxxx> writes:
...
>>> diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h
>>> index 73a035b40dbf..a6a5fbbf8504 100644
>>> --- a/arch/powerpc/kernel/head_32.h
>>> +++ b/arch/powerpc/kernel/head_32.h
>>> @@ -43,6 +43,7 @@
>>>  	.ifeq	\for_rtas
>>>  	li	r11, MSR_KERNEL & ~(MSR_IR | MSR_RI) /* can take DTLB miss */
>>>  	mtmsr	r11
>>> +	isync
>>
>> Actually this one leads to:
>>
>>   /home/michael/linux/arch/powerpc/kernel/head_8xx.S: Assembler messages:
>>   /home/michael/linux/arch/powerpc/kernel/head_8xx.S:151: Error:  
>> attempt to move .org backwards
>>   make[3]: *** [/home/michael/linux/scripts/Makefile.build:348:  
>> arch/powerpc/kernel/head_8xx.o] Error 1
>>
>> For mpc885_ads_defconfig.
>>
>> That's the alignment exception overflowing into the program check
>> handler:
>>
>> /* Alignment exception */
>> 	. = 0x600
>> Alignment:
>> 	EXCEPTION_PROLOG handle_dar_dsisr=1
>> 	save_dar_dsisr_on_stack r4, r5, r11
>> 	li	r6, RPN_PATTERN
>> 	mtspr	SPRN_DAR, r6	/* Tag DAR, to be used in DTLB Error */
>> 	addi	r3,r1,STACK_FRAME_OVERHEAD
>> 	EXC_XFER_STD(0x600, alignment_exception)
>>
>> /* Program check exception */
>> 	EXCEPTION(0x700, ProgramCheck, program_check_exception, EXC_XFER_STD)
>>
>>
>> Can't see an obvious/easy way to fix it.
>
> Argh !
>
> I think the easiest is to move the EXC_XFER_STD(0x600,  
> alignment_exception) somewhere else and branch to it. There is some  
> space at .0xa00

That works, or builds at least. I'm not setup to boot test it.

Does this look OK?

cheers