linux-kernel - Re: [PATCH v2 8/8] powerpc/entry: fix ppc syscall entry issues for common entry

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Message-ID: <E6A78B539A22183F+ZzRhLPuA7m_YcuvV@HX09040029.powercore.com.cn>
Date: Wed, 13 Nov 2024 16:19:56 +0800
From: Luming Yu <luming.yu@...ngroup.cn>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	mpe@...erman.id.au, npiggin@...il.com, christophe.leroy@...roup.eu,
	luming.yu@...il.com
Subject: Re: [PATCH v2 8/8] powerpc/entry: fix ppc syscall entry issues for
 common entry

On Wed, Nov 13, 2024 at 08:06:04AM +0100, Thomas Gleixner wrote:
> On Mon, Nov 11 2024 at 11:19, Luming Yu wrote:
> > Due to the common layer and internal calls details are hidden from
> > the top level at the call side in ppc arch code, there are some
> > difficulties in preserving
> > all semantics implications of the original code in the patch. e.g  when
> > we got -1 returned
> > from syscall_enter_from_user_mode, without touching common code, we have
> > to do
> > our own inference to recover the reasonable route to return, in order to
> > have correct errno
> > and syscall work behaviors,that are tested in seccomp_bpf 98 test
> > cases.
> 
> This indicates that your conversion to the common code is broken to
> begin with. Which is not surprising given the amount of issues I found
> already.
> 
> You need to sit down an come up with a proper conversion design and not
> just randomly replace things and then hack around the fallout later on.
> 
> If that requires changes to the core code, then they have to be designed
> up front and implemented in a way which does not affect existing users.
> 
> Thanks,
> 
>         tglx
Thanks for your time and the review comments. It is helpful.
The 3rd ver of the patch set should be able to address all these issues.
Going through v0 to v2, I think I've truely understood how came ppc64 that is stuck
in the halfway to be able to enjoy least code duplication while having fully function on top
of common entry code for so many key features. 
when the v1 is out, it is already too late to call back and the v2 was reluctantly out with
a random fix instead of clean conversion as you concluded just for making the hack working
as it was.  : -( 
> 
> 
>