Re: [PATCH v2] powerpc xmon: use `dcbf` inplace of `dcbi` instruction for 64bit Book3S

[Christophe Leroy <christophe.leroy@c-s.fr>]

Le 27/03/2020 à 10:03, Balamuruhan S a écrit :
> On Fri, 2020-03-27 at 07:48 +0100, Christophe Leroy wrote:
>>
>> Le 26/03/2020 à 07:15, Balamuruhan S a écrit :
>>> Data Cache Block Invalidate (dcbi) instruction was implemented back in
>>> PowerPC
>>> architecture version 2.03. It is obsolete and attempt to use of this
>>> illegal
>>> instruction results in a hypervisor emulation assistance interrupt. So,
>>> ifdef
>>> it out the option `i` in xmon for 64bit Book3S.
>>
>> I don't understand. You say two contradictory things:
>> 1/ You say it _was_ added back.
>> 2/ You say it _is_ obsolete.
>>
>> How can it be obsolete if it was added back ?
> 
> I actually learnt it from P8 and P9 User Manual,
> 
> The POWER8/POWER9 core does not provide support for the following optional or
> obsolete instructions (attempted use of these results in a hypervisor emulation
> assistance interrupt):
> • tlbia - TLB invalidate all
> • tlbiex - TLB invalidate entry by index (obsolete)
> • slbiex - SLB invalidate entry by index (obsolete)
> • dcba - Data cache block allocate (Book II; obsolete)
> • dcbi - Data cache block invalidate (obsolete)
> • rfi - Return from interrupt (32-bit; obsolete)
> 

Then that's exactly what you have to say in the coming log.

Maybe you could also change invalidate_dcache_range():

	for (i = 0; i < size >> shift; i++, addr += bytes) {
		if (IS_ENABLED(CONFIG_PPC_BOOK3S_64))
			dcbf(addr);
		else
			dcbi(addr);
	}




Christophe