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

[Conor Dooley <conor@kernel.org>]

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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
> 
> 
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> http://lists.infradead.org/mailman/listinfo/linux-riscv
> 

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