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Date: Tue, 16 Apr 2024 16:14:29 +0200
From: "Arnd Bergmann" <arnd@arndb.de>
To: "David Hildenbrand" <david@redhat.com>,
 "Miguel Ojeda" <miguel.ojeda.sandonis@gmail.com>,
 "Huacai Chen" <chenhuacai@kernel.org>, "WANG Xuerui" <kernel@xen0n.name>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
 "Ryan Roberts" <ryan.roberts@arm.com>,
 Linux-Arch <linux-arch@vger.kernel.org>, Linux-MM <linux-mm@kvack.org>,
 linux-kernel <linux-kernel@vger.kernel.org>, loongarch@lists.linux.dev,
 clang-built-linux <llvm@lists.linux.dev>
Subject: Re: ./include/asm-generic/tlb.h:629:10: error: parameter 'ptep' set but not
 used
Content-Type: text/plain

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.

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