[PATCH v4 4/4] mm: support Svnapot in huge vmap

[Conor.Dooley at microchip.com]

On 22/08/2022 16:34, panqinglin2020 at iscas.ac.cn wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> From: Qinglin Pan <panqinglin2020 at iscas.ac.cn>
> 
> The HAVE_ARCH_HUGE_VMAP option can be used to help implement arch
> special huge vmap size. This commit selects this option by default and
> re-writes the arch_vmap_pte_range_map_size for Svnapot 64KB size.
> 
> It can be tested when booting kernel in qemu with pci device, which
> will make the kernel to call pci driver using ioremap, and the
> re-written function will be called.
> 
> Signed-off-by: Qinglin Pan <panqinglin2020 at iscas.ac.cn>
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 9aaec147a860..a420325a24ac 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -70,6 +70,7 @@ config RISCV
>         select GENERIC_TIME_VSYSCALL if MMU && 64BIT
>         select GENERIC_VDSO_TIME_NS if HAVE_GENERIC_VDSO
>         select HAVE_ARCH_AUDITSYSCALL
> +       select HAVE_ARCH_HUGE_VMAP
>         select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL
>         select HAVE_ARCH_JUMP_LABEL_RELATIVE if !XIP_KERNEL
>         select HAVE_ARCH_KASAN if MMU && 64BIT
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index 37547dd04010..6d5caa1a6bd9 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -750,6 +750,43 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
>  }
>  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
> 
> +static inline int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
> +{
> +       return 0;
> +}
> +
> +static inline int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
> +{
> +       return 0;
> +}
> +
> +static inline void p4d_clear_huge(p4d_t *p4d) { }
> +
> +static inline int pud_clear_huge(pud_t *pud)
> +{
> +       return 0;
> +}
> +
> +static inline int pmd_clear_huge(pmd_t *pmd)
> +{
> +       return 0;
> +}
> +
> +static inline int p4d_free_pud_page(p4d_t *p4d, unsigned long addr)
> +{
> +       return 0;
> +}
> +
> +static inline int pud_free_pmd_page(pud_t *pud, unsigned long addr)
> +{
> +       return 0;
> +}
> +
> +static inline int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)
> +{
> +       return 0;
> +}
> +
>  /*
>   * Encode and decode a swap entry
>   *
> diff --git a/arch/riscv/include/asm/vmalloc.h b/arch/riscv/include/asm/vmalloc.h
> index ff9abc00d139..d92880fbfcde 100644
> --- a/arch/riscv/include/asm/vmalloc.h
> +++ b/arch/riscv/include/asm/vmalloc.h
> @@ -1,4 +1,26 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
>  #ifndef _ASM_RISCV_VMALLOC_H
>  #define _ASM_RISCV_VMALLOC_H
> 
> +#include <linux/pgtable.h>
> +
> +#ifdef CONFIG_SVNAPOT
> +#define arch_vmap_pte_range_map_size vmap_pte_range_map_size
> +static inline unsigned long vmap_pte_range_map_size(unsigned long addr,
> +                                                   unsigned long end,
> +                                                   u64 pfn,
> +                                                   unsigned int max_page_shift)

How about:

static inline unsigned long
vmap_pte_range_map_size(unsigned long addr, unsigned long end, u64 pfn,
			unsigned int max_page_shift)
{
?
> +{
> +       bool is_napot_addr = !(addr & NAPOT_CONT64KB_MASK);
> +       bool pfn_align_napot = !(pfn & (NAPOT_64KB_PTE_NUM - 1UL));
> +       bool space_enough = ((end - addr) >= NAPOT_CONT64KB_SIZE);
> +

tbh I would rather see this early return for each of these failed
tests rather than lump them all into the below. Prob can do the same
for each of them.. Personally I find that more readable than what you
have here. /shrug

Thanks,
Conor.

> +       if (has_svnapot() && is_napot_addr && pfn_align_napot &&
> +           space_enough && max_page_shift >= NAPOT_CONT64KB_SHIFT)
> +               return NAPOT_CONT64KB_SIZE;

> +
> +       return PAGE_SIZE;
> +}
> +#endif /*CONFIG_SVNAPOT*/
> +
>  #endif /* _ASM_RISCV_VMALLOC_H */
> --
> 2.35.1
> 
> 
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