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Message-ID: <6ad0c386-6777-4467-bab4-8fba149f3bfe@ghiti.fr>
Date: Thu, 18 Jul 2024 18:43:05 +0200
From: Alexandre Ghiti <alex@...ti.fr>
To: Yong-Xuan Wang <yongxuan.wang@...ive.com>, linux-kernel@...r.kernel.org,
linux-riscv@...ts.infradead.org, kvm-riscv@...ts.infradead.org,
kvm@...r.kernel.org
Cc: greentime.hu@...ive.com, vincent.chen@...ive.com,
Jinyu Tang <tjytimi@....com>, Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
Andrew Jones <ajones@...tanamicro.com>, Anup Patel <anup@...infault.org>,
Conor Dooley <conor.dooley@...rochip.com>,
Mayuresh Chitale <mchitale@...tanamicro.com>,
Atish Patra <atishp@...osinc.com>, Samuel Ortiz <sameo@...osinc.com>,
Daniel Henrique Barboza <dbarboza@...tanamicro.com>,
Samuel Holland <samuel.holland@...ive.com>,
Clément Léger <cleger@...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>, Leonardo Bras <leobras@...hat.com>,
Charlie Jenkins <charlie@...osinc.com>,
"Matthew Wilcox (Oracle)" <willy@...radead.org>,
Jisheng Zhang <jszhang@...nel.org>
Subject: Re: [PATCH v7 1/4] RISC-V: Add Svade and Svadu Extensions Support
Hi Yong-Xuan,
On 12/07/2024 10:38, 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@....com>
> Signed-off-by: Jinyu Tang <tjytimi@....com>
> Signed-off-by: Yong-Xuan Wang <yongxuan.wang@...ive.com>
> Reviewed-by: Andrew Jones <ajones@...tanamicro.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
> 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
> +#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.
Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>
Thanks,
Alex
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