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Message-ID: <97898777-8129-4ce9-8ae4-9d4bbc2a5a26@ghiti.fr>
Date: Tue, 5 Nov 2024 14:13:17 +0100
From: Alexandre Ghiti <alex@...ti.fr>
To: Chunyan Zhang <zhangchunyan@...as.ac.cn>,
Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
<palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
Chunyan Zhang <zhang.lyra@...il.com>
Subject: Re: [RESEND PATCH V4 2/3] riscv: mm: Add soft-dirty page tracking
support
On 30/08/2024 03:11, Chunyan Zhang wrote:
> The PTE bit(9) is reserved for software, now used by DEVMAP,
> this patch reuse bit(9) for soft-dirty which is enabled only
s/reuse/reuses
> if !CONFIG_ARCH_HAS_PTE_DEVMAP, in other words, soft-dirty
> and devmap will be mutually exclusive on RISC-V.
>
> To add swap PTE soft-dirty tracking, we borrow bit (4) which is
> available for swap PTEs on RISC-V systems.
>
> Signed-off-by: Chunyan Zhang <zhangchunyan@...as.ac.cn>
> ---
> arch/riscv/Kconfig | 27 ++++++++++-
> arch/riscv/include/asm/pgtable-bits.h | 12 +++++
> arch/riscv/include/asm/pgtable.h | 69 ++++++++++++++++++++++++++-
> 3 files changed, 106 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 0f3cd7c3a436..f1460fc01cd4 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -39,7 +39,6 @@ config RISCV
> select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> select ARCH_HAS_PMEM_API
> select ARCH_HAS_PREPARE_SYNC_CORE_CMD
> - select ARCH_HAS_PTE_DEVMAP if 64BIT && MMU
> select ARCH_HAS_PTE_SPECIAL
> select ARCH_HAS_SET_DIRECT_MAP if MMU
> select ARCH_HAS_SET_MEMORY if MMU
> @@ -948,6 +947,32 @@ config RANDOMIZE_BASE
>
> If unsure, say N.
>
> +choice
> + prompt "PET RSW Bit(9) used for"
I would say: "PTE RSW bit(9) usage"
> + default RISCV_HAS_PTE_DEVMEP
s/DEVMEP/DEVMAP
> + depends on MMU && 64BIT
> + help
> + RISC-V PTE bit(9) is reserved for software, and used by more than
> + one kernel features which cannot be supported at the same time.
s/features/feature
> + So we have to select one for it.
> +
> +config RISCV_HAS_PTE_DEVMEP
> + bool "DEVMAP mark"
I would say simply "devmap"
> + select ARCH_HAS_PTE_DEVMAP
> + help
> + The PTE bit(9) is used for DEVMAP mark. ZONE_DEVICE pages need DEVMAP
"is used for devmap...pages need devmap"
> + PTEs support to function.
> +
> + So if you want to use ZONE_DEVICE, select this.
> +
> +config RISCV_HAS_SOFT_DIRTY
> + bool "soft dirty"
s/soft dirty/soft-dirty
> + select HAVE_ARCH_SOFT_DIRTY
> + help
> + The PTE bit(9) is used for soft-dirty tracking.
> +
> +endchoice
> +
> endmenu # "Kernel features"
>
> menu "Boot options"
> diff --git a/arch/riscv/include/asm/pgtable-bits.h b/arch/riscv/include/asm/pgtable-bits.h
> index 5bcc73430829..c6d51fe9fc6f 100644
> --- a/arch/riscv/include/asm/pgtable-bits.h
> +++ b/arch/riscv/include/asm/pgtable-bits.h
> @@ -26,6 +26,18 @@
> #define _PAGE_DEVMAP 0
> #endif /* CONFIG_ARCH_HAS_PTE_DEVMAP */
>
> +#ifdef CONFIG_MEM_SOFT_DIRTY
For consistency with CONFIG_ARCH_HAS_PTE_DEVMAP, I would use
CONFIG_HAVE_ARCH_SOFT_DIRTY
> +#define _PAGE_SOFT_DIRTY (1 << 9) /* RSW: 0x2 for software dirty tracking */
> +/*
> + * BIT 4 is not involved into swap entry computation, so we
> + * can borrow it for swap page soft-dirty tracking.
> + */
> +#define _PAGE_SWP_SOFT_DIRTY _PAGE_USER
> +#else
> +#define _PAGE_SOFT_DIRTY 0
> +#define _PAGE_SWP_SOFT_DIRTY 0
> +#endif /* CONFIG_MEM_SOFT_DIRTY */
Same here.
> +
> #define _PAGE_TABLE _PAGE_PRESENT
>
> /*
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index 089f3c9f56a3..d41507919ef2 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -428,7 +428,7 @@ static inline pte_t pte_mkwrite_novma(pte_t pte)
>
> static inline pte_t pte_mkdirty(pte_t pte)
> {
> - return __pte(pte_val(pte) | _PAGE_DIRTY);
> + return __pte(pte_val(pte) | _PAGE_DIRTY | _PAGE_SOFT_DIRTY);
> }
>
> static inline pte_t pte_mkclean(pte_t pte)
> @@ -461,6 +461,38 @@ static inline pte_t pte_mkhuge(pte_t pte)
> return pte;
> }
>
> +#ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
> +static inline int pte_soft_dirty(pte_t pte)
> +{
> + return pte_val(pte) & _PAGE_SOFT_DIRTY;
> +}
> +
> +static inline pte_t pte_mksoft_dirty(pte_t pte)
> +{
> + return __pte(pte_val(pte) | _PAGE_SOFT_DIRTY);
> +}
> +
> +static inline pte_t pte_clear_soft_dirty(pte_t pte)
> +{
> + return __pte(pte_val(pte) & ~(_PAGE_SOFT_DIRTY));
> +}
> +
> +static inline int pte_swp_soft_dirty(pte_t pte)
> +{
> + return pte_val(pte) & _PAGE_SWP_SOFT_DIRTY;
> +}
> +
> +static inline pte_t pte_swp_mksoft_dirty(pte_t pte)
> +{
> + return __pte(pte_val(pte) | _PAGE_SWP_SOFT_DIRTY);
> +}
> +
> +static inline pte_t pte_swp_clear_soft_dirty(pte_t pte)
> +{
> + return __pte(pte_val(pte) & ~(_PAGE_SWP_SOFT_DIRTY));
> +}
> +#endif /* CONFIG_HAVE_ARCH_SOFT_DIRTY */
> +
> #ifdef CONFIG_RISCV_ISA_SVNAPOT
> #define pte_leaf_size(pte) (pte_napot(pte) ? \
> napot_cont_size(napot_cont_order(pte)) :\
> @@ -751,6 +783,40 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
> return pte_pmd(pte_mkdevmap(pmd_pte(pmd)));
> }
>
> +#ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
> +static inline int pmd_soft_dirty(pmd_t pmd)
> +{
> + return pte_soft_dirty(pmd_pte(pmd));
> +}
> +
> +static inline pmd_t pmd_mksoft_dirty(pmd_t pmd)
> +{
> + return pte_pmd(pte_mksoft_dirty(pmd_pte(pmd)));
> +}
> +
> +static inline pmd_t pmd_clear_soft_dirty(pmd_t pmd)
> +{
> + return pte_pmd(pte_clear_soft_dirty(pmd_pte(pmd)));
> +}
> +
> +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
> +static inline int pmd_swp_soft_dirty(pmd_t pmd)
> +{
> + return pte_swp_soft_dirty(pmd_pte(pmd));
> +}
> +
> +static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd)
> +{
> + return pte_pmd(pte_swp_mksoft_dirty(pmd_pte(pmd)));
> +}
> +
> +static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd)
> +{
> + return pte_pmd(pte_swp_clear_soft_dirty(pmd_pte(pmd)));
> +}
> +#endif /* CONFIG_ARCH_ENABLE_THP_MIGRATION */
> +#endif /* CONFIG_HAVE_ARCH_SOFT_DIRTY */
> +
> static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
> pmd_t *pmdp, pmd_t pmd)
> {
> @@ -841,6 +907,7 @@ extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
> * Format of swap PTE:
> * bit 0: _PAGE_PRESENT (zero)
> * bit 1 to 3: _PAGE_LEAF (zero)
> + * bit 4: _PAGE_SWP_SOFT_DIRTY
> * bit 5: _PAGE_PROT_NONE (zero)
> * bit 6: exclusive marker
> * bits 7 to 11: swap type
Apart from the minor things above, the rest looks good so you can add:
Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>
Thanks,
Alex
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