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Message-ID: <20240527-41b376a2bfedb3b9cf7e9c7b@orel>
Date: Mon, 27 May 2024 18:25:49 +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, 
	kvm@...r.kernel.org, greentime.hu@...ive.com, vincent.chen@...ive.com, 
	cleger@...osinc.com, alex@...ti.fr, Jinyu Tang <tjytimi@....com>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Anup Patel <anup@...infault.org>, 
	Conor Dooley <conor.dooley@...rochip.com>, Mayuresh Chitale <mchitale@...tanamicro.com>, 
	Samuel Holland <samuel.holland@...ive.com>, Samuel Ortiz <sameo@...osinc.com>, 
	Evan Green <evan@...osinc.com>, Xiao Wang <xiao.w.wang@...el.com>, 
	Alexandre Ghiti <alexghiti@...osinc.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Kemeng Shi <shikemeng@...weicloud.com>, "Mike Rapoport (IBM)" <rppt@...nel.org>, 
	Jisheng Zhang <jszhang@...nel.org>, "Matthew Wilcox (Oracle)" <willy@...radead.org>, 
	Charlie Jenkins <charlie@...osinc.com>, Leonardo Bras <leobras@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v4 1/5] RISC-V: Detect and Enable Svadu Extension
 Support

On Fri, May 24, 2024 at 06:33:01PM GMT, Yong-Xuan Wang wrote:
> Svadu is a RISC-V extension for hardware updating of PTE A/D bits.
> 
> In this patch we detect Svadu extension support from DTB and enable it
> with SBI FWFT extension. Also we 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>
> Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>
> Reviewed-by: Andrew Jones <ajones@...tanamicro.com>

I think this patch changed too much to keep r-b's. We didn't have the
FWFT part before.

> ---
>  arch/riscv/Kconfig               |  1 +
>  arch/riscv/include/asm/csr.h     |  1 +
>  arch/riscv/include/asm/hwcap.h   |  1 +
>  arch/riscv/include/asm/pgtable.h |  8 +++++++-
>  arch/riscv/kernel/cpufeature.c   | 11 +++++++++++
>  5 files changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index be09c8836d56..30fa558ee284 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -34,6 +34,7 @@ config RISCV
>  	select ARCH_HAS_PMEM_API
>  	select ARCH_HAS_PREPARE_SYNC_CORE_CMD
>  	select ARCH_HAS_PTE_SPECIAL
> +	select ARCH_HAS_HW_PTE_YOUNG
>  	select ARCH_HAS_SET_DIRECT_MAP if MMU
>  	select ARCH_HAS_SET_MEMORY if MMU
>  	select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
> diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
> index 2468c55933cd..2ac270ad4acd 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_ADUE			(_AC(1, ULL) << 61)
>  #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 e17d0078a651..8d539e3f4e11 100644
> --- a/arch/riscv/include/asm/hwcap.h
> +++ b/arch/riscv/include/asm/hwcap.h
> @@ -81,6 +81,7 @@
>  #define RISCV_ISA_EXT_ZTSO		72
>  #define RISCV_ISA_EXT_ZACAS		73
>  #define RISCV_ISA_EXT_XANDESPMU		74
> +#define RISCV_ISA_EXT_SVADU		75
>  
>  #define RISCV_ISA_EXT_XLINUXENVCFG	127
>  
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index 9f8ea0e33eb1..1f1b326ccf63 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -117,6 +117,7 @@
>  #include <asm/tlbflush.h>
>  #include <linux/mm_types.h>
>  #include <asm/compat.h>
> +#include <asm/cpufeature.h>
>  
>  #define __page_val_to_pfn(_val)  (((_val) & _PAGE_PFN_MASK) >> _PAGE_PFN_SHIFT)
>  
> @@ -285,7 +286,6 @@ static inline pte_t pud_pte(pud_t pud)
>  }
>  
>  #ifdef CONFIG_RISCV_ISA_SVNAPOT
> -#include <asm/cpufeature.h>
>  
>  static __always_inline bool has_svnapot(void)
>  {
> @@ -621,6 +621,12 @@ 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 3ed2359eae35..b023908c5932 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -93,6 +93,16 @@ static bool riscv_isa_extension_check(int id)
>  			return false;
>  		}
>  		return true;
> +	case RISCV_ISA_EXT_SVADU:
> +		if (sbi_probe_extension(SBI_EXT_FWFT) > 0) {

I think we've decided the appropriate way to prove for SBI extensions is
to first ensure the SBI version and then do the probe, like we do for STA
in has_pv_steal_clock()

> +			struct sbiret ret;
> +
> +			ret = sbi_ecall(SBI_EXT_FWFT, SBI_EXT_FWFT_SET, SBI_FWFT_PTE_AD_HW_UPDATING,
> +					1, 0, 0, 0, 0);
> +
> +			return ret.error == SBI_SUCCESS;
> +		}
> +		return false;
>  	case RISCV_ISA_EXT_INVALID:
>  		return false;
>  	}
> @@ -301,6 +311,7 @@ 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_SUPERSET(svadu, RISCV_ISA_EXT_SVADU, riscv_xlinuxenvcfg_exts),

We do we need XLINUXENVCFG?

Thanks,
drew

>  	__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
> 

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