[PATCH v7 1/4] RISC-V: Add Svade and Svadu Extensions Support

[Samuel Holland]

Hi Yong-Xuan,

Two trivial comments below for if you send another version of the series.

On 2024-07-12 3:38 AM, Yong-Xuan Wang wrote:
> Svade and Svadu extensions represent two schemes for managing the PTE A/D
> bits. When the PTE A/D bits need to be set, Svade extension intdicates
> that a related page fault will be raised. In contrast, the Svadu extension
> supports hardware updating of PTE A/D bits. Since the Svade extension is
> mandatory and the Svadu extension is optional in RVA23 profile, by default
> the M-mode firmware will enable the Svadu extension in the menvcfg CSR
> when only Svadu is present in DT.
> 
> This patch detects Svade and Svadu extensions from DT and adds
> arch_has_hw_pte_young() to enable optimization in MGLRU and
> __wp_page_copy_user() when we have the PTE A/D bits hardware updating
> support.
> 
> Co-developed-by: Jinyu Tang <tjytimi at 163.com>
> Signed-off-by: Jinyu Tang <tjytimi at 163.com>
> Signed-off-by: Yong-Xuan Wang <yongxuan.wang at sifive.com>
> Reviewed-by: Andrew Jones <ajones at ventanamicro.com>
> ---
>  arch/riscv/Kconfig               |  1 +
>  arch/riscv/include/asm/csr.h     |  1 +
>  arch/riscv/include/asm/hwcap.h   |  2 ++
>  arch/riscv/include/asm/pgtable.h | 13 ++++++++++++-
>  arch/riscv/kernel/cpufeature.c   | 32 ++++++++++++++++++++++++++++++++
>  5 files changed, 48 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 0525ee2d63c7..3d705e28ff85 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -36,6 +36,7 @@ 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

These lines should be sorted alphabetically.

>  	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 25966995da04..524cd4131c71 100644
> --- a/arch/riscv/include/asm/csr.h
> +++ b/arch/riscv/include/asm/csr.h
> @@ -195,6 +195,7 @@
>  /* 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..35d7aa49785d 100644
> --- a/arch/riscv/include/asm/hwcap.h
> +++ b/arch/riscv/include/asm/hwcap.h
> @@ -81,6 +81,8 @@
>  #define RISCV_ISA_EXT_ZTSO		72
>  #define RISCV_ISA_EXT_ZACAS		73
>  #define RISCV_ISA_EXT_XANDESPMU		74
> +#define RISCV_ISA_EXT_SVADE             75

The number here should be aligned with tabs, like the surrounding lines.

Regards,
Samuel

> +#define RISCV_ISA_EXT_SVADU		76
>  
>  #define RISCV_ISA_EXT_XLINUXENVCFG	127
>  
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index aad8b8ca51f1..ec0cdacd7da0 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -120,6 +120,7 @@
>  #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)
>  
> @@ -288,7 +289,6 @@ 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)
>  {
> @@ -624,6 +624,17 @@ static inline pgprot_t pgprot_writecombine(pgprot_t _prot)
>  	return __pgprot(prot);
>  }
>  
> +/*
> + * Both Svade and Svadu control the hardware behavior when the PTE A/D bits need to be set. By
> + * default the M-mode firmware enables the hardware updating scheme when only Svadu is present in
> + * DT.
> + */
> +#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 5ef48cb20ee1..b2c3fe945e89 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -301,6 +301,8 @@ 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(svade, RISCV_ISA_EXT_SVADE),
> +	__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),
> @@ -554,6 +556,21 @@ static void __init riscv_fill_hwcap_from_isa_string(unsigned long *isa2hwcap)
>  			clear_bit(RISCV_ISA_EXT_v, isainfo->isa);
>  		}
>  
> +		/*
> +		 * When neither Svade nor Svadu present in DT, it is technically
> +		 * unknown whether the platform uses Svade or Svadu. Supervisor may
> +		 * assume Svade to be present and enabled or it can discover based
> +		 * on mvendorid, marchid, and mimpid. When both Svade and Svadu present
> +		 * in DT, supervisor must assume Svadu turned-off at boot time. To use
> +		 * Svadu, supervisor must explicitly enable it using the SBI FWFT extension.
> +		 */
> +		if (!test_bit(RISCV_ISA_EXT_SVADE, isainfo->isa) &&
> +		    !test_bit(RISCV_ISA_EXT_SVADU, isainfo->isa))
> +			set_bit(RISCV_ISA_EXT_SVADE, isainfo->isa);
> +		else if (test_bit(RISCV_ISA_EXT_SVADE, isainfo->isa) &&
> +			 test_bit(RISCV_ISA_EXT_SVADU, isainfo->isa))
> +			clear_bit(RISCV_ISA_EXT_SVADU, isainfo->isa);
> +
>  		/*
>  		 * All "okay" hart should have same isa. Set HWCAP based on
>  		 * common capabilities of every "okay" hart, in case they don't
> @@ -619,6 +636,21 @@ static int __init riscv_fill_hwcap_from_ext_list(unsigned long *isa2hwcap)
>  
>  		of_node_put(cpu_node);
>  
> +		/*
> +		 * When neither Svade nor Svadu present in DT, it is technically
> +		 * unknown whether the platform uses Svade or Svadu. Supervisor may
> +		 * assume Svade to be present and enabled or it can discover based
> +		 * on mvendorid, marchid, and mimpid. When both Svade and Svadu present
> +		 * in DT, supervisor must assume Svadu turned-off at boot time. To use
> +		 * Svadu, supervisor must explicitly enable it using the SBI FWFT extension.
> +		 */
> +		if (!test_bit(RISCV_ISA_EXT_SVADE, isainfo->isa) &&
> +		    !test_bit(RISCV_ISA_EXT_SVADU, isainfo->isa))
> +			set_bit(RISCV_ISA_EXT_SVADE, isainfo->isa);
> +		else if (test_bit(RISCV_ISA_EXT_SVADE, isainfo->isa) &&
> +			 test_bit(RISCV_ISA_EXT_SVADU, isainfo->isa))
> +			clear_bit(RISCV_ISA_EXT_SVADU, isainfo->isa);
> +
>  		/*
>  		 * All "okay" harts should have same isa. Set HWCAP based on
>  		 * common capabilities of every "okay" hart, in case they don't.