linux-kernel - Re: ./include/asm-generic/tlb.h:629:10: error: parameter 'ptep' set but not used

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Date: Tue, 16 Apr 2024 22:41:22 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Arnd Bergmann <arnd@...db.de>
Cc: David Hildenbrand <david@...hat.com>, Miguel Ojeda <miguel.ojeda.sandonis@...il.com>, 
	WANG Xuerui <kernel@...0n.name>, Andrew Morton <akpm@...ux-foundation.org>, 
	Ryan Roberts <ryan.roberts@....com>, Linux-Arch <linux-arch@...r.kernel.org>, 
	Linux-MM <linux-mm@...ck.org>, linux-kernel <linux-kernel@...r.kernel.org>, 
	loongarch@...ts.linux.dev, clang-built-linux <llvm@...ts.linux.dev>
Subject: Re: ./include/asm-generic/tlb.h:629:10: error: parameter 'ptep' set
 but not used

On Tue, Apr 16, 2024 at 10:14 PM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Tue, Apr 16, 2024, at 15:51, David Hildenbrand wrote:
> > On 16.04.24 12:26, Miguel Ojeda wrote:
> >> Hi David, Arnd, LoongArch,
> >>
> >> In a linux-next defconfig LLVM=1 build today I got:
> >>
> >>      ./include/asm-generic/tlb.h:629:10: error: parameter 'ptep' set
> >> but not used [-Werror,-Wunused-but-set-parameter]
> >>        629 |                 pte_t *ptep, unsigned int nr, unsigned long address)
> >>            |                        ^
> >>
> >> Indeed, in loongarch, `__tlb_remove_tlb_entry` does not do anything.
> >> This seems the same that Arnd reported for arm64:
> >>
> >>      https://lore.kernel.org/all/20240221154549.2026073-1-arnd@kernel.org/
> >>
> >> So perhaps the loongarch's one should also be changed into an static inline?
> >
> > 4d5bf0b6183f79ea361dd506365d2a471270735c is already part of v6.9-rc1. How come
> > we see that only now on linux-next?
>
> Andrew merged my patch to enable -Wextra yesterday, and it appears
> that this one fell through the cracks with my testing, either I
> missed the combination of loongarch with clang, or I last tested
> it before your patches got merged.
>
> > I assume we should see the same on upstream Linux with LLVM=1, correct?
>
> On upstream, it only shows up with 'make W=1'.
>
> > If so, we should likely just drop that completely and rely on the
> > asm-generic one:
> >
> > diff --git a/arch/loongarch/include/asm/tlb.h
> > b/arch/loongarch/include/asm/tlb.h
> > index da7a3b5b9374a..e071f5e9e8580 100644
> > --- a/arch/loongarch/include/asm/tlb.h
> > +++ b/arch/loongarch/include/asm/tlb.h
> > @@ -132,8 +132,6 @@ static __always_inline void invtlb_all(u32 op, u32
> > info, u64 addr)
> >                  );
> >   }
> >
> > -#define __tlb_remove_tlb_entry(tlb, ptep, address) do { } while (0)
> > -
> >   static void tlb_flush(struct mmu_gather *tlb);
>
> Yes, this looks like the best solution, and I can confirm that this
> addresses the warning on linux-next.
Emmm, this should be removed in the first place because x86 removed it
at 5.12...

Huacai
>
> Tested-by: Arnd Bergmann <arnd@...db.de>