Re: [PATCH 1/4] LoongArch: mm: Add page table mapped mode support

[Huacai Chen <chenhuacai@kernel.org>]

Hi, Enze,

On Wed, Jul 19, 2023 at 4:34 PM Enze Li <lienze@kylinos.cn> wrote:
>
> According to LoongArch documentation online, there are two types of address
> translation modes: direct mapped address translation mode (direct mapped mode)
> and page table mapped address translation mode (page table mapped mode).
>
> Currently, the upstream code only supports DMM (Direct Mapped Mode).
> This patch adds a function that determines whether PTMM (Page Table
> Mapped Mode) should be used, and also adds the corresponding handler
> funcitons for both modes.
>
> For more details on the two modes, see [1].
>
> [1] https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#virtual-address-space-and-address-translation-mode
>
> Signed-off-by: Enze Li <lienze@kylinos.cn>
> ---
>  arch/loongarch/include/asm/page.h    | 10 ++++++++++
>  arch/loongarch/include/asm/pgtable.h |  6 ++++++
>  arch/loongarch/mm/pgtable.c          | 25 +++++++++++++++++++++++++
>  3 files changed, 41 insertions(+)
>
> diff --git a/arch/loongarch/include/asm/page.h b/arch/loongarch/include/asm/page.h
> index 26e8dccb6619..05919be15801 100644
> --- a/arch/loongarch/include/asm/page.h
> +++ b/arch/loongarch/include/asm/page.h
> @@ -84,7 +84,17 @@ typedef struct { unsigned long pgprot; } pgprot_t;
>  #define sym_to_pfn(x)          __phys_to_pfn(__pa_symbol(x))
>
>  #define virt_to_pfn(kaddr)     PFN_DOWN(PHYSADDR(kaddr))
> +
> +#ifdef CONFIG_64BIT
> +#define virt_to_page(kaddr)                                            \
> +({                                                                     \
> +       is_PTMM_addr((unsigned long)kaddr) ?                            \
> +       PTMM_virt_to_page((unsigned long)kaddr) :                       \
> +       DMM_virt_to_page((unsigned long)kaddr);                         \
> +})
1, Rename these helpers to
is_dmw_addr()/dmw_virt_to_page()/tlb_virt_to_page() will be better.
2, These helpers are so simple so can be defined as inline function or
macros in page.h.
3, CONFIG_64BIT can be removed here.

Huacai

> +#else
>  #define virt_to_page(kaddr)    pfn_to_page(virt_to_pfn(kaddr))
> +#endif
>
>  extern int __virt_addr_valid(volatile void *kaddr);
>  #define virt_addr_valid(kaddr) __virt_addr_valid((volatile void *)(kaddr))
> diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h
> index ed6a37bb55b5..0fc074b8bd48 100644
> --- a/arch/loongarch/include/asm/pgtable.h
> +++ b/arch/loongarch/include/asm/pgtable.h
> @@ -360,6 +360,12 @@ static inline void pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *pt
>  #define PMD_T_LOG2     (__builtin_ffs(sizeof(pmd_t)) - 1)
>  #define PTE_T_LOG2     (__builtin_ffs(sizeof(pte_t)) - 1)
>
> +#ifdef CONFIG_64BIT
> +struct page *DMM_virt_to_page(unsigned long kaddr);
> +struct page *PTMM_virt_to_page(unsigned long kaddr);
> +bool is_PTMM_addr(unsigned long kaddr);
> +#endif
> +
>  extern pgd_t swapper_pg_dir[];
>  extern pgd_t invalid_pg_dir[];
>
> diff --git a/arch/loongarch/mm/pgtable.c b/arch/loongarch/mm/pgtable.c
> index 36a6dc0148ae..4c6448f996b6 100644
> --- a/arch/loongarch/mm/pgtable.c
> +++ b/arch/loongarch/mm/pgtable.c
> @@ -9,6 +9,31 @@
>  #include <asm/pgtable.h>
>  #include <asm/tlbflush.h>
>
> +#ifdef CONFIG_64BIT
> +/* DMM stands for Direct Mapped Mode. */
> +struct page *DMM_virt_to_page(unsigned long kaddr)
> +{
> +       return pfn_to_page(virt_to_pfn(kaddr));
> +}
> +EXPORT_SYMBOL_GPL(DMM_virt_to_page);
> +
> +/* PTMM stands for Page Table Mapped Mode. */
> +struct page *PTMM_virt_to_page(unsigned long kaddr)
> +{
> +       return pte_page(*virt_to_kpte(kaddr));
> +}
> +EXPORT_SYMBOL_GPL(PTMM_virt_to_page);
> +
> +bool is_PTMM_addr(unsigned long kaddr)
> +{
> +       if (unlikely((kaddr & GENMASK(BITS_PER_LONG - 1, cpu_vabits)) ==
> +                    GENMASK(BITS_PER_LONG - 1, cpu_vabits)))
> +               return true;
> +       return false;
> +}
> +EXPORT_SYMBOL_GPL(is_PTMM_addr);
> +#endif
> +
>  pgd_t *pgd_alloc(struct mm_struct *mm)
>  {
>         pgd_t *ret, *init;
> --
> 2.34.1
>
>