linux-kernel - Re: [PATCH v2 1/3] RISC-V: Detect and Enable Svadu Extension Support

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Message-ID: <20230927-62fbd3d63f4c6ffada90b7ee@orel>
Date:   Wed, 27 Sep 2023 09:03:38 +0200
From:   Andrew Jones <ajones@...tanamicro.com>
To:     Yong-Xuan Wang <yongxuan.wang@...ive.com>
Cc:     linux-riscv@...ts.infradead.org, kvm-riscv@...ts.infradead.org,
        greentime.hu@...ive.com, vincent.chen@...ive.com, tjytimi@....com,
        alex@...ti.fr, Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <apatel@...tanamicro.com>,
        Guo Ren <guoren@...nel.org>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Daniel Henrique Barboza <dbarboza@...tanamicro.com>,
        wchen <waylingii@...il.com>, Heiko Stuebner <heiko@...ech.de>,
        Jisheng Zhang <jszhang@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexandre Ghiti <alexghiti@...osinc.com>,
        Kemeng Shi <shikemeng@...weicloud.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Charlie Jenkins <charlie@...osinc.com>,
        Sergey Matyukevich <sergey.matyukevich@...tacore.com>,
        David Hildenbrand <david@...hat.com>,
        Qinglin Pan <panqinglin2020@...as.ac.cn>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Sunil V L <sunilvl@...tanamicro.com>,
        Evan Green <evan@...osinc.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] RISC-V: Detect and Enable Svadu Extension Support

On Fri, Sep 22, 2023 at 08:56:47AM +0000, Yong-Xuan Wang wrote:
> We detect Svadu extension support from DTB and add arch_has_hw_pte_young()
> to enable optimization in MGLRU and __wp_page_copy_user() if Svadu
> extension is available.
> 
> Co-developed-by: Jinyu Tang <tjytimi@....com>
> Signed-off-by: Jinyu Tang <tjytimi@....com>
> Signed-off-by: Yong-Xuan Wang <yongxuan.wang@...ive.com>
> ---
>  arch/riscv/include/asm/csr.h     | 1 +
>  arch/riscv/include/asm/hwcap.h   | 1 +
>  arch/riscv/include/asm/pgtable.h | 6 ++++++
>  arch/riscv/kernel/cpufeature.c   | 1 +
>  4 files changed, 9 insertions(+)
> 
> diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
> index 777cb8299551..10648b372a2a 100644
> --- a/arch/riscv/include/asm/csr.h
> +++ b/arch/riscv/include/asm/csr.h
> @@ -194,6 +194,7 @@
>  /* xENVCFG flags */
>  #define ENVCFG_STCE			(_AC(1, ULL) << 63)
>  #define ENVCFG_PBMTE			(_AC(1, ULL) << 62)
> +#define ENVCFG_HADE			(_AC(1, ULL) << 61)

This bit is named 'ADUE' in the spec. Why are we calling it HADE?

>  #define ENVCFG_CBZE			(_AC(1, UL) << 7)
>  #define ENVCFG_CBCFE			(_AC(1, UL) << 6)
>  #define ENVCFG_CBIE_SHIFT		4
> diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
> index b7b58258f6c7..1013661d6516 100644
> --- a/arch/riscv/include/asm/hwcap.h
> +++ b/arch/riscv/include/asm/hwcap.h
> @@ -58,6 +58,7 @@
>  #define RISCV_ISA_EXT_ZICSR		40
>  #define RISCV_ISA_EXT_ZIFENCEI		41
>  #define RISCV_ISA_EXT_ZIHPM		42
> +#define RISCV_ISA_EXT_SVADU		43
>  
>  #define RISCV_ISA_EXT_MAX		64
>  
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index b2ba3f79cfe9..028b700cd27b 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -629,6 +629,12 @@ static inline pgprot_t pgprot_writecombine(pgprot_t _prot)
>  	return __pgprot(prot);
>  }
>  
> +#define arch_has_hw_pte_young arch_has_hw_pte_young
> +static inline bool arch_has_hw_pte_young(void)
> +{
> +	return riscv_has_extension_unlikely(RISCV_ISA_EXT_SVADU);
> +}
> +
>  /*
>   * THP functions
>   */
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 1cfbba65d11a..ead378c04991 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -178,6 +178,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
>  	__RISCV_ISA_EXT_DATA(ssaia, RISCV_ISA_EXT_SSAIA),
>  	__RISCV_ISA_EXT_DATA(sscofpmf, RISCV_ISA_EXT_SSCOFPMF),
>  	__RISCV_ISA_EXT_DATA(sstc, RISCV_ISA_EXT_SSTC),
> +	__RISCV_ISA_EXT_DATA(svadu, RISCV_ISA_EXT_SVADU),
>  	__RISCV_ISA_EXT_DATA(svinval, RISCV_ISA_EXT_SVINVAL),
>  	__RISCV_ISA_EXT_DATA(svnapot, RISCV_ISA_EXT_SVNAPOT),
>  	__RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT),
> -- 
> 2.17.1
>

Thanks,
drew