linux-kernel - Re: [PATCH] riscv: Support huge pfnmaps

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Message-ID: <CAHVXubjw44raXLX568wcUc0AeUva6vSjwY710WPxGk4=5vpO7g@mail.gmail.com>
Date: Wed, 8 Jan 2025 15:04:59 +0100
From: Alexandre Ghiti <alexghiti@...osinc.com>
To: Andrew Bresticker <abrestic@...osinc.com>
Cc: Palmer Dabbelt <palmer@...belt.com>, linux-riscv@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, Peter Xu <peterx@...hat.com>
Subject: Re: [PATCH] riscv: Support huge pfnmaps

Hi Andrew,

On Wed, Jan 8, 2025 at 2:57 PM Andrew Bresticker <abrestic@...osinc.com> wrote:
>
> Use RSW0 as the special bit for pmds and puds, just like for ptes.
> Also define the {pte,pmd,pud}_pgprot helpers which were previously
> missing and are needed for the follow_pfnmap APIs.
>
> Signed-off-by: Andrew Bresticker <abrestic@...osinc.com>
> ---
>  arch/riscv/Kconfig               |  1 +
>  arch/riscv/include/asm/pgtable.h | 49 ++++++++++++++++++++++++++++++++
>  2 files changed, 50 insertions(+)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index d4a7ca0388c0..ff4849e35545 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -61,6 +61,7 @@ config RISCV
>         select ARCH_SUPPORTS_ATOMIC_RMW
>         select ARCH_SUPPORTS_CFI_CLANG
>         select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
> +       select ARCH_SUPPORTS_HUGE_PFNMAP if TRANSPARENT_HUGEPAGE
>         select ARCH_SUPPORTS_HUGETLBFS if MMU
>         # LLD >= 14: https://github.com/llvm/llvm-project/issues/50505
>         select ARCH_SUPPORTS_LTO_CLANG if LLD_VERSION >= 140000
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index d4e99eef90ac..95ee745e3ef7 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -341,6 +341,14 @@ static inline pte_t pfn_pte(unsigned long pfn, pgprot_t prot)
>
>  #define mk_pte(page, prot)       pfn_pte(page_to_pfn(page), prot)
>
> +#define pte_pgprot pte_pgprot
> +static inline pgprot_t pte_pgprot(pte_t pte)
> +{
> +       unsigned long pfn = pte_pfn(pte);
> +
> +       return __pgprot(pte_val(pfn_pte(pfn, __pgprot(0))) ^ pte_val(pte));
> +}
> +
>  static inline int pte_present(pte_t pte)
>  {
>         return (pte_val(pte) & (_PAGE_PRESENT | _PAGE_PROT_NONE));
> @@ -674,6 +682,11 @@ static inline pmd_t pte_pmd(pte_t pte)
>         return __pmd(pte_val(pte));
>  }
>
> +static inline pud_t pte_pud(pte_t pte)
> +{
> +       return __pud(pte_val(pte));
> +}
> +
>  static inline pmd_t pmd_mkhuge(pmd_t pmd)
>  {
>         return pmd;
> @@ -699,6 +712,18 @@ static inline unsigned long pud_pfn(pud_t pud)
>         return ((__pud_to_phys(pud) & PUD_MASK) >> PAGE_SHIFT);
>  }
>
> +#define pmd_pgprot pmd_pgprot
> +static inline pgprot_t pmd_pgprot(pmd_t pmd)
> +{
> +       return pte_pgprot(pmd_pte(pmd));
> +}
> +
> +#define pud_pgprot pud_pgprot
> +static inline pgprot_t pud_pgprot(pud_t pud)
> +{
> +       return pte_pgprot(pud_pte(pud));
> +}
> +
>  static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
>  {
>         return pte_pmd(pte_modify(pmd_pte(pmd), newprot));
> @@ -768,6 +793,30 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
>         return pte_pmd(pte_mkdevmap(pmd_pte(pmd)));
>  }
>
> +#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
> +static inline bool pmd_special(pmd_t pmd)
> +{
> +       return pte_special(pmd_pte(pmd));
> +}
> +
> +static inline pmd_t pmd_mkspecial(pmd_t pmd)
> +{
> +       return pte_pmd(pte_mkspecial(pmd_pte(pmd)));
> +}
> +#endif
> +
> +#ifdef CONFIG_ARCH_SUPPORTS_PUD_PFNMAP
> +static inline bool pud_special(pud_t pud)
> +{
> +       return pte_special(pud_pte(pud));
> +}
> +
> +static inline pud_t pud_mkspecial(pud_t pud)
> +{
> +       return pte_pud(pte_mkspecial(pud_pte(pud)));
> +}
> +#endif
> +
>  static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
>                                 pmd_t *pmdp, pmd_t pmd)
>  {
> --
> 2.34.1
>

Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>

Thanks,

Alex