Re: [PATCH v9 2/3] riscv: mm: support Svnapot in hugetlb page

Conor Dooley
2022-12-07T18:55:34Z

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On Sun, Dec 04, 2022 at 10:11:36PM +0800, panqinglin2020@iscas.ac.cn wrote:
> From: Qinglin Pan <panqinglin2020@iscas.ac.cn>
>
> Svnapot can be used to support 64KB hugetlb page, so it can become a new
> option when using hugetlbfs. Add a basic implementation of hugetlb page,
> and support 64KB as a size in it by using Svnapot.
>
> For test, boot kernel with command line contains "default_hugepagesz=64K
> hugepagesz=64K hugepages=20" and run a simple test like this:
>
> tools/testing/selftests/vm/map_hugetlb 1 16
>
> And it should be passed.
>
> Signed-off-by: Qinglin Pan <panqinglin2020@iscas.ac.cn>
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 1d8477c0af7c..be5c1edea70f 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -43,7 +43,7 @@ config RISCV
> select ARCH_USE_QUEUED_RWLOCKS
> select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
> select ARCH_WANT_FRAME_POINTERS
> - select ARCH_WANT_GENERAL_HUGETLB
> + select ARCH_WANT_GENERAL_HUGETLB if !RISCV_ISA_SVNAPOT

I am expecting this to be a dumb question too, but I'm curious again
about what happens in a system that enables CONFIG_RISCV_ISA_SVNAPOT but
the platform it is running on does not support it...

> select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
> select ARCH_WANTS_THP_SWAP if HAVE_ARCH_TRANSPARENT_HUGEPAGE
> select BINFMT_FLAT_NO_DATA_START_OFFSET if !MMU
> diff --git a/arch/riscv/include/asm/hugetlb.h b/arch/riscv/include/asm/hugetlb.h
> index ec19d6afc896..fe6f23006641 100644
> --- a/arch/riscv/include/asm/hugetlb.h
> +++ b/arch/riscv/include/asm/hugetlb.h
> @@ -2,7 +2,6 @@
> #ifndef _ASM_RISCV_HUGETLB_H
> #define _ASM_RISCV_HUGETLB_H
>
> -#include <asm-generic/hugetlb.h>
> #include <asm/page.h>
>
> static inline void arch_clear_hugepage_flags(struct page *page)
> @@ -11,4 +10,37 @@ static inline void arch_clear_hugepage_flags(struct page *page)
> }
> #define arch_clear_hugepage_flags arch_clear_hugepage_flags
>
> +#ifdef CONFIG_RISCV_ISA_SVNAPOT
> +#define __HAVE_ARCH_HUGE_PTE_CLEAR
> +void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
> + pte_t *ptep, unsigned long sz);
> +
> +#define __HAVE_ARCH_HUGE_SET_HUGE_PTE_AT
> +void set_huge_pte_at(struct mm_struct *mm,
> + unsigned long addr, pte_t *ptep, pte_t pte);
> +
> +#define __HAVE_ARCH_HUGE_PTEP_GET_AND_CLEAR
> +pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
> + unsigned long addr, pte_t *ptep);
> +
> +#define __HAVE_ARCH_HUGE_PTEP_CLEAR_FLUSH
> +pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
> + unsigned long addr, pte_t *ptep);
> +
> +#define __HAVE_ARCH_HUGE_PTEP_SET_WRPROTECT
> +void huge_ptep_set_wrprotect(struct mm_struct *mm,
> + unsigned long addr, pte_t *ptep);
> +
> +#define __HAVE_ARCH_HUGE_PTEP_SET_ACCESS_FLAGS
> +int huge_ptep_set_access_flags(struct vm_area_struct *vma,
> + unsigned long addr, pte_t *ptep,
> + pte_t pte, int dirty);
> +
> +pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags);
> +#define arch_make_huge_pte arch_make_huge_pte
> +
> +#endif /*CONFIG_RISCV_ISA_SVNAPOT*/
> +
> +#include <asm-generic/hugetlb.h>

...is this sufficient to fall back to generic huge pages?

Hopefully that's just my ignorance on show!

Thanks,
Conor.

> +
> #endif /* _ASM_RISCV_HUGETLB_H */
> diff --git a/arch/riscv/mm/hugetlbpage.c b/arch/riscv/mm/hugetlbpage.c
> index 932dadfdca54..49f92f8cd431 100644
> --- a/arch/riscv/mm/hugetlbpage.c
> +++ b/arch/riscv/mm/hugetlbpage.c
> @@ -2,6 +2,301 @@
> #include <linux/hugetlb.h>
> #include <linux/err.h>
>
> +#ifdef CONFIG_RISCV_ISA_SVNAPOT
> +pte_t *huge_pte_alloc(struct mm_struct *mm,
> + struct vm_area_struct *vma,
> + unsigned long addr,
> + unsigned long sz)
> +{
> + pgd_t *pgd;
> + p4d_t *p4d;
> + pud_t *pud;
> + pmd_t *pmd;
> + pte_t *pte = NULL;
> + unsigned long order;
> +
> + pgd = pgd_offset(mm, addr);
> + p4d = p4d_alloc(mm, pgd, addr);
> + if (!p4d)
> + return NULL;
> +
> + pud = pud_alloc(mm, p4d, addr);
> + if (!pud)
> + return NULL;
> +
> + if (sz == PUD_SIZE) {
> + pte = (pte_t *)pud;
> + goto out;
> + }
> +
> + if (sz == PMD_SIZE) {
> + if (want_pmd_share(vma, addr) && pud_none(*pud))
> + pte = huge_pmd_share(mm, vma, addr, pud);
> + else
> + pte = (pte_t *)pmd_alloc(mm, pud, addr);
> + goto out;
> + }
> +
> + pmd = pmd_alloc(mm, pud, addr);
> + if (!pmd)
> + return NULL;
> +
> + for_each_napot_order(order) {
> + if (napot_cont_size(order) == sz) {
> + pte = pte_alloc_map(mm, pmd, (addr & napot_cont_mask(order)));
> + break;
> + }
> + }
> +
> +out:
> + WARN_ON_ONCE(pte && pte_present(*pte) && !pte_huge(*pte));
> + return pte;
> +}
> +
> +pte_t *huge_pte_offset(struct mm_struct *mm,
> + unsigned long addr,
> + unsigned long sz)
> +{
> + pgd_t *pgd;
> + p4d_t *p4d;
> + pud_t *pud;
> + pmd_t *pmd;
> + pte_t *pte = NULL;
> + unsigned long order;
> +
> + pgd = pgd_offset(mm, addr);
> + if (!pgd_present(*pgd))
> + return NULL;
> + p4d = p4d_offset(pgd, addr);
> + if (!p4d_present(*p4d))
> + return NULL;
> +
> + pud = pud_offset(p4d, addr);
> + if (sz == PUD_SIZE)
> + /* must be pud huge, non-present or none */
> + return (pte_t *)pud;
> + if (!pud_present(*pud))
> + return NULL;
> +
> + pmd = pmd_offset(pud, addr);
> + if (sz == PMD_SIZE)
> + /* must be pmd huge, non-present or none */
> + return (pte_t *)pmd;
> + if (!pmd_present(*pmd))
> + return NULL;
> +
> + for_each_napot_order(order) {
> + if (napot_cont_size(order) == sz) {
> + pte = pte_offset_kernel(pmd, (addr & napot_cont_mask(order)));
> + break;
> + }
> + }
> + return pte;
> +}
> +
> +static pte_t get_clear_contig(struct mm_struct *mm,
> + unsigned long addr,
> + pte_t *ptep,
> + unsigned long pte_num)
> +{
> + pte_t orig_pte = ptep_get(ptep);
> + unsigned long i;
> +
> + for (i = 0; i < pte_num; i++, addr += PAGE_SIZE, ptep++) {
> + pte_t pte = ptep_get_and_clear(mm, addr, ptep);
> +
> + if (pte_dirty(pte))
> + orig_pte = pte_mkdirty(orig_pte);
> +
> + if (pte_young(pte))
> + orig_pte = pte_mkyoung(orig_pte);
> + }
> + return orig_pte;
> +}
> +
> +static pte_t get_clear_contig_flush(struct mm_struct *mm,
> + unsigned long addr,
> + pte_t *ptep,
> + unsigned long pte_num)
> +{
> + pte_t orig_pte = get_clear_contig(mm, addr, ptep, pte_num);
> + bool valid = !pte_none(orig_pte);
> + struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
> +
> + if (valid)
> + flush_tlb_range(&vma, addr, addr + (PAGE_SIZE * pte_num));
> +
> + return orig_pte;
> +}
> +
> +pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags)
> +{
> + unsigned long order;
> +
> + for_each_napot_order(order) {
> + if (shift == napot_cont_shift(order)) {
> + entry = pte_mknapot(entry, order);
> + break;
> + }
> + }
> + if (order == NAPOT_ORDER_MAX)
> + entry = pte_mkhuge(entry);
> +
> + return entry;
> +}
> +
> +void set_huge_pte_at(struct mm_struct *mm,
> + unsigned long addr,
> + pte_t *ptep,
> + pte_t pte)
> +{
> + int i;
> + int pte_num;
> +
> + if (!pte_napot(pte)) {
> + set_pte_at(mm, addr, ptep, pte);
> + return;
> + }
> +
> + pte_num = napot_pte_num(napot_cont_order(pte));
> + for (i = 0; i < pte_num; i++, ptep++, addr += PAGE_SIZE)
> + set_pte_at(mm, addr, ptep, pte);
> +}
> +
> +int huge_ptep_set_access_flags(struct vm_area_struct *vma,
> + unsigned long addr,
> + pte_t *ptep,
> + pte_t pte,
> + int dirty)
> +{
> + pte_t orig_pte;
> + int i;
> + int pte_num;
> + struct mm_struct *mm = vma->vm_mm;
> +
> + if (!pte_napot(pte))
> + return ptep_set_access_flags(vma, addr, ptep, pte, dirty);
> +
> + pte_num = napot_pte_num(napot_cont_order(pte));
> + ptep = huge_pte_offset(mm, addr,
> + napot_cont_size(napot_cont_order(pte)));
> + orig_pte = get_clear_contig_flush(mm, addr, ptep, pte_num);
> +
> + if (pte_dirty(orig_pte))
> + pte = pte_mkdirty(pte);
> +
> + if (pte_young(orig_pte))
> + pte = pte_mkyoung(pte);
> +
> + for (i = 0; i < pte_num; i++, addr += PAGE_SIZE, ptep++)
> + set_pte_at(mm, addr, ptep, pte);
> +
> + return true;
> +}
> +
> +pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
> + unsigned long addr,
> + pte_t *ptep)
> +{
> + int pte_num;
> + pte_t orig_pte = ptep_get(ptep);
> +
> + if (!pte_napot(orig_pte))
> + return ptep_get_and_clear(mm, addr, ptep);
> +
> + pte_num = napot_pte_num(napot_cont_order(orig_pte));
> +
> + return get_clear_contig(mm, addr, ptep, pte_num);
> +}
> +
> +void huge_ptep_set_wrprotect(struct mm_struct *mm,
> + unsigned long addr,
> + pte_t *ptep)
> +{
> + int i;
> + int pte_num;
> + pte_t pte = ptep_get(ptep);
> +
> + if (!pte_napot(pte)) {
> + ptep_set_wrprotect(mm, addr, ptep);
> + return;
> + }
> +
> + pte_num = napot_pte_num(napot_cont_order(pte));
> + ptep = huge_pte_offset(mm, addr, napot_cont_size(napot_cont_order(pte)));
> +
> + for (i = 0; i < pte_num; i++, addr += PAGE_SIZE, ptep++)
> + ptep_set_wrprotect(mm, addr, ptep);
> +}
> +
> +pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
> + unsigned long addr,
> + pte_t *ptep)
> +{
> + int pte_num;
> + pte_t pte = ptep_get(ptep);
> +
> + if (!pte_napot(pte))
> + return ptep_clear_flush(vma, addr, ptep);
> +
> + pte_num = napot_pte_num(napot_cont_order(pte));
> +
> + return get_clear_contig_flush(vma->vm_mm, addr, ptep, pte_num);
> +}
> +
> +void huge_pte_clear(struct mm_struct *mm,
> + unsigned long addr,
> + pte_t *ptep,
> + unsigned long sz)
> +{
> + int i, pte_num;
> + pte_t pte = READ_ONCE(*ptep);
> +
> + if (!pte_napot(pte)) {
> + pte_clear(mm, addr, ptep);
> + return;
> + }
> +
> + pte_num = napot_pte_num(napot_cont_order(pte));
> + for (i = 0; i < pte_num; i++, addr += PAGE_SIZE, ptep++)
> + pte_clear(mm, addr, ptep);
> +}
> +
> +bool __init is_napot_size(unsigned long size)
> +{
> + unsigned long order;
> +
> + if (!has_svnapot())
> + return false;
> +
> + for_each_napot_order(order) {
> + if (size == napot_cont_size(order))
> + return true;
> + }
> + return false;
> +}
> +
> +static __init int napot_hugetlbpages_init(void)
> +{
> + if (has_svnapot()) {
> + unsigned long order;
> +
> + for_each_napot_order(order)
> + hugetlb_add_hstate(order);
> + }
> + return 0;
> +}
> +arch_initcall(napot_hugetlbpages_init);
> +
> +#else
> +
> +bool __init is_napot_size(unsigned long size)
> +{
> + return false;
> +}
> +
> +#endif /*CONFIG_RISCV_ISA_SVNAPOT*/
> +
> int pud_huge(pud_t pud)
> {
> return pud_leaf(pud);
> @@ -18,6 +313,8 @@ bool __init arch_hugetlb_valid_size(unsigned long size)
> return true;
> else if (IS_ENABLED(CONFIG_64BIT) && size == PUD_SIZE)
> return true;
> + else if (is_napot_size(size))
> + return true;
> else
> return false;
> }
> --
> 2.37.4
>
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
>

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