[PATCH v7] powerpc/irq: Inline call_do_irq() and call_do_softirq()

[Michael Ellerman]

Christophe Leroy <christophe.leroy at csgroup.eu> writes:
> Le 20/03/2021 à 13:22, Michael Ellerman a écrit :
>> From: Christophe Leroy <christophe.leroy at csgroup.eu>
>> 
>> call_do_irq() and call_do_softirq() are simple enough to be
>> worth inlining.
>> 
>> Inlining them avoids an mflr/mtlr pair plus a save/reload on stack. It
>> also allows GCC to keep the saved ksp_limit in an nonvolatile reg.
>
> We don't have the ksp_limit anymore, I forgot to remove the above text.

No worries, I'll edit it when I apply it.

>> This is inspired from S390 arch. Several other arches do more or
>> less the same. The way sparc arch does seems odd thought.
>> 
>> Signed-off-by: Christophe Leroy <christophe.leroy at csgroup.eu>
>> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
>> ---
>> 
>> v2: no change.
>> v3: no change.
>> v4:
>> - comment reminding the purpose of the inline asm block.
>> - added r2 as clobbered reg
>> v5:
>> - Limiting the change to PPC32 for now.
>> - removed r2 from the clobbered regs list (on PPC32 r2 points to current all the time)
>> - Removed patch 1 and merged ksp_limit handling in here.
>> v6:
>> - Rebase on top of merge-test (ca6e327fefb2).
>> - Remove the ksp_limit stuff as it's doesn't exist anymore.
>> 
>> v7:
>> mpe:
>> - Enable for 64-bit too. This all in-kernel code calling in-kernel
>>    code, and must use the kernel TOC.
>
> Great.
>
>> - Use named parameters for the inline asm.
>
> Hmm. It is the first time we use named parameters in powerpc assembly, isn't it ?

Not quite the first.

See load_unaligned_zeropad().

And also my soon to be merged code in:
  http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20210211135130.3474832-5-mpe@ellerman.id.au/

> I saw when investigating userspace access that x86 is using named parameters widely.

Yeah I'd like us to use it more, I think it helps readability a lot.

> Wondering, how would the below look like with named parameters (from __put_user_asm2_goto) ?
>
> 	stw%X1 %L0, %L1

Not sure, possibly that's too complicated for it :)

cheers