linux-kernel - Re: [PATCH v3 5/8] LoongArch: Simplify the invtlb wrappers

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Message-ID: <b0a6db96-1062-ce90-f8da-b9866b3c8166@loongson.cn>
Date:   Tue, 27 Jun 2023 17:29:29 +0800
From:   bibo mao <maobibo@...ngson.cn>
To:     WANG Xuerui <kernel@...0n.name>,
        Huacai Chen <chenhuacai@...nel.org>
Cc:     WANG Rui <wangrui@...ngson.cn>, Xi Ruoyao <xry111@...111.site>,
        loongarch@...ts.linux.dev, linux-kbuild@...r.kernel.org,
        llvm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        WANG Xuerui <git@...0n.name>
Subject: Re: [PATCH v3 5/8] LoongArch: Simplify the invtlb wrappers



在 2023/6/25 17:56, WANG Xuerui 写道:
> From: WANG Xuerui <git@...0n.name>
> 
> The invtlb instruction has been supported by upstream LoongArch
> toolchains from day one, so ditch the raw opcode trickery and just use
> plain inline asm for it.
> 
> While at it, also make the invtlb asm statements barriers, for proper
> modeling of the side effects. The functions are also marked as
> __always_inline instead of just "inline", because they cannot work at
> all if not inlined: the op argument will not be compile-time const in
> that case, thus failing to satisfy the "i" constraint.
> 
> The signature of the other more specific invtlb wrappers contain unused
> arguments right now, but these are not removed right away in order for
> the patch to be focused. In the meantime, assertions are added to ensure
> no accidental misuse happens before the refactor. (The more specific
> wrappers cannot re-use the generic invtlb wrapper, because the ISA
> manual says $zero shall be used in case a particular op does not take
> the respective argument: re-using the generic wrapper would mean losing
> control over the register usage.)
> 
> Signed-off-by: WANG Xuerui <git@...0n.name>
> ---
>  arch/loongarch/include/asm/tlb.h | 43 ++++++++++++++------------------
>  1 file changed, 19 insertions(+), 24 deletions(-)
> 
> diff --git a/arch/loongarch/include/asm/tlb.h b/arch/loongarch/include/asm/tlb.h
> index 0dc9ee2b05d2..da7a3b5b9374 100644
> --- a/arch/loongarch/include/asm/tlb.h
> +++ b/arch/loongarch/include/asm/tlb.h
> @@ -88,52 +88,47 @@ enum invtlb_ops {
>  	INVTLB_GID_ADDR = 0x16,
>  };
>  
> -/*
> - * invtlb op info addr
> - * (0x1 << 26) | (0x24 << 20) | (0x13 << 15) |
> - * (addr << 10) | (info << 5) | op
> - */
> -static inline void invtlb(u32 op, u32 info, u64 addr)
> +static __always_inline void invtlb(u32 op, u32 info, u64 addr)
>  {
>  	__asm__ __volatile__(
> -		"parse_r addr,%0\n\t"
> -		"parse_r info,%1\n\t"
> -		".word ((0x6498000) | (addr << 10) | (info << 5) | %2)\n\t"
> -		:
> -		: "r"(addr), "r"(info), "i"(op)
> +		"invtlb %0, %1, %2\n\t"
>  		:
> +		: "i"(op), "r"(info), "r"(addr)
> +		: "memory"
>  		);
>  }
>  
> -static inline void invtlb_addr(u32 op, u32 info, u64 addr)
> +static __always_inline void invtlb_addr(u32 op, u32 info, u64 addr)
>  {
> +	BUILD_BUG_ON(!__builtin_constant_p(info) || info != 0);
>  	__asm__ __volatile__(
> -		"parse_r addr,%0\n\t"
> -		".word ((0x6498000) | (addr << 10) | (0 << 5) | %1)\n\t"
> -		:
> -		: "r"(addr), "i"(op)
> +		"invtlb %0, $zero, %1\n\t"
>  		:
> +		: "i"(op), "r"(addr)
> +		: "memory"
>  		);
>  }
>  
> -static inline void invtlb_info(u32 op, u32 info, u64 addr)
> +static __always_inline void invtlb_info(u32 op, u32 info, u64 addr)
>  {
> +	BUILD_BUG_ON(!__builtin_constant_p(addr) || addr != 0);
>  	__asm__ __volatile__(
> -		"parse_r info,%0\n\t"
> -		".word ((0x6498000) | (0 << 10) | (info << 5) | %1)\n\t"
> -		:
> -		: "r"(info), "i"(op)
> +		"invtlb %0, %1, $zero\n\t"
>  		:
> +		: "i"(op), "r"(info)
> +		: "memory"
>  		);
>  }
macro parse_r is not used here, and it is not used any more.
Can you remove definition of this macro also?

Regards
Bibo Mao

>  
> -static inline void invtlb_all(u32 op, u32 info, u64 addr)
> +static __always_inline void invtlb_all(u32 op, u32 info, u64 addr)
>  {
> +	BUILD_BUG_ON(!__builtin_constant_p(info) || info != 0);
> +	BUILD_BUG_ON(!__builtin_constant_p(addr) || addr != 0);
>  	__asm__ __volatile__(
> -		".word ((0x6498000) | (0 << 10) | (0 << 5) | %0)\n\t"
> +		"invtlb %0, $zero, $zero\n\t"
>  		:
>  		: "i"(op)
> -		:
> +		: "memory"
>  		);
>  }
>