Re: [PATCH v5 18/22] powerpc/syscall: Remove FULL_REGS verification in system_call_exception

Nicholas Piggin
2021-02-10T02:28:29Z

Excerpts from Christophe Leroy's message of February 10, 2021 12:31 am:
>
>
> Le 09/02/2021 à 03:02, Nicholas Piggin a écrit :
>> Excerpts from Christophe Leroy's message of February 9, 2021 1:10 am:
>>> For book3s/64, FULL_REGS() is 'true' at all time, so the test voids.
>>> For others, non volatile registers are saved inconditionally.
>>>
>>> So the verification is pointless.
>>>
>>> Should one fail to do it, it would anyway be caught by the
>>> CHECK_FULL_REGS() in copy_thread() as we have removed the
>>> special versions ppc_fork() and friends.
>>>
>>> null_syscall benchmark reduction 4 cycles (332 => 328 cycles)
>>
>> I wonder if we rather make a CONFIG option for a bunch of these simpler
>> debug checks here (and also in interrupt exit, wrappers, etc) rather
>> than remove them entirely.
>
> We can drop this patch if you prefer. Anyway, like book3s/64, once ppc32 also do interrupt
> entry/exit in C, FULL_REGS() will already return true.

Sure let's do that.

Thanks,
Nick