Re: [PATCH 1/4] LoongArch: Set pte entry with PAGE_GLOBAL for kernel space

[Huacai Chen]

Hi, Bibo,

On Thu, Oct 10, 2024 at 11:50 AM Bibo Mao <maobibo@xxxxxxxxxxx> wrote:
>
> Unlike general architectures, there are two pages for one TLB entry
> on LoongArch system. For kernel space, it requires both two pte
> entries with PAGE_GLOBAL set, else HW treats it as non-global tlb,
> there will be potential problems if tlb entry for kernel space is
> not global. Such as fail to flush kernel tlb with function
> local_flush_tlb_kernel_range() which only flush tlb with global bit.
>
> Here function kernel_pte_init() is added, it can be used to init
> pte table when it is created, so the default inital pte is
> PAGE_GLOBAL rather than zero at beginning.
I think kernel_pte_init() is also needed in zero_pmd_populate() in
mm/kasan/init.c. And moreover, the second patch should be squashed in
this one because they should be as a whole. Though the second one
touches the common code, I can merge it with mm maintainer's acked-by.


Huacai

>
> Kernel space areas includes fixmap, percpu, vmalloc and kasan areas
> set default pte entry with PAGE_GLOBAL set.
>
> Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx>
> ---
>  arch/loongarch/include/asm/pgalloc.h | 13 +++++++++++++
>  arch/loongarch/include/asm/pgtable.h |  1 +
>  arch/loongarch/mm/init.c             |  4 +++-
>  arch/loongarch/mm/kasan_init.c       |  4 +++-
>  arch/loongarch/mm/pgtable.c          | 22 ++++++++++++++++++++++
>  5 files changed, 42 insertions(+), 2 deletions(-)
>
> diff --git a/arch/loongarch/include/asm/pgalloc.h b/arch/loongarch/include/asm/pgalloc.h
> index 4e2d6b7ca2ee..b2698c03dc2c 100644
> --- a/arch/loongarch/include/asm/pgalloc.h
> +++ b/arch/loongarch/include/asm/pgalloc.h
> @@ -10,8 +10,21 @@
>
>  #define __HAVE_ARCH_PMD_ALLOC_ONE
>  #define __HAVE_ARCH_PUD_ALLOC_ONE
> +#define __HAVE_ARCH_PTE_ALLOC_ONE_KERNEL
>  #include <asm-generic/pgalloc.h>
>
> +static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
> +{
> +       pte_t *pte;
> +
> +       pte = (pte_t *) __get_free_page(GFP_KERNEL);
> +       if (!pte)
> +               return NULL;
> +
> +       kernel_pte_init(pte);
> +       return pte;
> +}
> +
>  static inline void pmd_populate_kernel(struct mm_struct *mm,
>                                        pmd_t *pmd, pte_t *pte)
>  {
> diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h
> index 9965f52ef65b..22e3a8f96213 100644
> --- a/arch/loongarch/include/asm/pgtable.h
> +++ b/arch/loongarch/include/asm/pgtable.h
> @@ -269,6 +269,7 @@ extern void set_pmd_at(struct mm_struct *mm, unsigned long addr, pmd_t *pmdp, pm
>  extern void pgd_init(void *addr);
>  extern void pud_init(void *addr);
>  extern void pmd_init(void *addr);
> +extern void kernel_pte_init(void *addr);
>
>  /*
>   * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
> diff --git a/arch/loongarch/mm/init.c b/arch/loongarch/mm/init.c
> index 8a87a482c8f4..9f26e933a8a3 100644
> --- a/arch/loongarch/mm/init.c
> +++ b/arch/loongarch/mm/init.c
> @@ -198,9 +198,11 @@ pte_t * __init populate_kernel_pte(unsigned long addr)
>         if (!pmd_present(pmdp_get(pmd))) {
>                 pte_t *pte;
>
> -               pte = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
> +               pte = memblock_alloc_raw(PAGE_SIZE, PAGE_SIZE);
>                 if (!pte)
>                         panic("%s: Failed to allocate memory\n", __func__);
> +
> +               kernel_pte_init(pte);
>                 pmd_populate_kernel(&init_mm, pmd, pte);
>         }
>
> diff --git a/arch/loongarch/mm/kasan_init.c b/arch/loongarch/mm/kasan_init.c
> index 427d6b1aec09..34988573b0d5 100644
> --- a/arch/loongarch/mm/kasan_init.c
> +++ b/arch/loongarch/mm/kasan_init.c
> @@ -152,6 +152,8 @@ static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
>                 phys_addr_t page_phys = early ?
>                                         __pa_symbol(kasan_early_shadow_page)
>                                               : kasan_alloc_zeroed_page(node);
> +               if (!early)
> +                       kernel_pte_init(__va(page_phys));
>                 next = addr + PAGE_SIZE;
>                 set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
>         } while (ptep++, addr = next, addr != end && __pte_none(early, ptep_get(ptep)));
> @@ -287,7 +289,7 @@ void __init kasan_init(void)
>                 set_pte(&kasan_early_shadow_pte[i],
>                         pfn_pte(__phys_to_pfn(__pa_symbol(kasan_early_shadow_page)), PAGE_KERNEL_RO));
>
> -       memset(kasan_early_shadow_page, 0, PAGE_SIZE);
> +       kernel_pte_init(kasan_early_shadow_page);
>         csr_write64(__pa_symbol(swapper_pg_dir), LOONGARCH_CSR_PGDH);
>         local_flush_tlb_all();
>
> diff --git a/arch/loongarch/mm/pgtable.c b/arch/loongarch/mm/pgtable.c
> index eb6a29b491a7..228ffc1db0a3 100644
> --- a/arch/loongarch/mm/pgtable.c
> +++ b/arch/loongarch/mm/pgtable.c
> @@ -38,6 +38,28 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
>  }
>  EXPORT_SYMBOL_GPL(pgd_alloc);
>
> +void kernel_pte_init(void *addr)
> +{
> +       unsigned long *p, *end;
> +       unsigned long entry;
> +
> +       entry = (unsigned long)_PAGE_GLOBAL;
> +       p = (unsigned long *)addr;
> +       end = p + PTRS_PER_PTE;
> +
> +       do {
> +               p[0] = entry;
> +               p[1] = entry;
> +               p[2] = entry;
> +               p[3] = entry;
> +               p[4] = entry;
> +               p += 8;
> +               p[-3] = entry;
> +               p[-2] = entry;
> +               p[-1] = entry;
> +       } while (p != end);
> +}
> +
>  void pgd_init(void *addr)
>  {
>         unsigned long *p, *end;
> --
> 2.39.3
>