Subject: Re: [PATCH v4 15/34] x86: Convert various functions to use ptdescs

From: Mike Rapoport <[email-masked]>
Date: Wed, 14 Jun 2023 17:27:26 +0300

On Mon, Jun 12, 2023 at 02:04:04PM -0700, Vishal Moola (Oracle) wrote:
> In order to split struct ptdesc from struct page, convert various
> functions to use ptdescs.
> 
> Some of the functions use the *get*page*() helper functions. Convert

Nit:                           *get_free_page*()

> these to use pagetable_alloc() and ptdesc_address() instead to help
> standardize page tables further.

More importantly, get_free_pages() ensures a page won't be allocated from
HIGHMEM, and for 32-bits this is a must.
 
> Signed-off-by: Vishal Moola (Oracle) <[email-masked]>
> ---
>  arch/x86/mm/pgtable.c | 46 +++++++++++++++++++++++++------------------
>  1 file changed, 27 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
> index 15a8009a4480..6da7fd5d4782 100644
> --- a/arch/x86/mm/pgtable.c
> +++ b/arch/x86/mm/pgtable.c
> @@ -52,7 +52,7 @@ early_param("userpte", setup_userpte);
>  
>  void ___pte_free_tlb(struct mmu_gather *tlb, struct page *pte)
>  {
> -	pgtable_pte_page_dtor(pte);
> +	pagetable_pte_dtor(page_ptdesc(pte));
>  	paravirt_release_pte(page_to_pfn(pte));
>  	paravirt_tlb_remove_table(tlb, pte);
>  }
> @@ -60,7 +60,7 @@ void ___pte_free_tlb(struct mmu_gather *tlb, struct page *pte)
>  #if CONFIG_PGTABLE_LEVELS > 2
>  void ___pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd)
>  {
> -	struct page *page = virt_to_page(pmd);
> +	struct ptdesc *ptdesc = virt_to_ptdesc(pmd);
>  	paravirt_release_pmd(__pa(pmd) >> PAGE_SHIFT);
>  	/*
>  	 * NOTE! For PAE, any changes to the top page-directory-pointer-table
> @@ -69,8 +69,8 @@ void ___pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd)
>  #ifdef CONFIG_X86_PAE
>  	tlb->need_flush_all = 1;
>  #endif
> -	pgtable_pmd_page_dtor(page);
> -	paravirt_tlb_remove_table(tlb, page);
> +	pagetable_pmd_dtor(ptdesc);
> +	paravirt_tlb_remove_table(tlb, ptdesc_page(ptdesc));
>  }
>  
>  #if CONFIG_PGTABLE_LEVELS > 3
> @@ -92,16 +92,16 @@ void ___p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d)
>  
>  static inline void pgd_list_add(pgd_t *pgd)
>  {
> -	struct page *page = virt_to_page(pgd);
> +	struct ptdesc *ptdesc = virt_to_ptdesc(pgd);
>  
> -	list_add(&page->lru, &pgd_list);
> +	list_add(&ptdesc->pt_list, &pgd_list);
>  }
>  
>  static inline void pgd_list_del(pgd_t *pgd)
>  {
> -	struct page *page = virt_to_page(pgd);
> +	struct ptdesc *ptdesc = virt_to_ptdesc(pgd);
>  
> -	list_del(&page->lru);
> +	list_del(&ptdesc->pt_list);
>  }
>  
>  #define UNSHARED_PTRS_PER_PGD				\
> @@ -112,12 +112,12 @@ static inline void pgd_list_del(pgd_t *pgd)
>  
>  static void pgd_set_mm(pgd_t *pgd, struct mm_struct *mm)
>  {
> -	virt_to_page(pgd)->pt_mm = mm;
> +	virt_to_ptdesc(pgd)->pt_mm = mm;
>  }
>  
>  struct mm_struct *pgd_page_get_mm(struct page *page)
>  {
> -	return page->pt_mm;
> +	return page_ptdesc(page)->pt_mm;
>  }
>  
>  static void pgd_ctor(struct mm_struct *mm, pgd_t *pgd)
> @@ -213,11 +213,14 @@ void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd)
>  static void free_pmds(struct mm_struct *mm, pmd_t *pmds[], int count)
>  {
>  	int i;
> +	struct ptdesc *ptdesc;
>  
>  	for (i = 0; i < count; i++)
>  		if (pmds[i]) {
> -			pgtable_pmd_page_dtor(virt_to_page(pmds[i]));
> -			free_page((unsigned long)pmds[i]);
> +			ptdesc = virt_to_ptdesc(pmds[i]);
> +
> +			pagetable_pmd_dtor(ptdesc);
> +			pagetable_free(ptdesc);
>  			mm_dec_nr_pmds(mm);
>  		}
>  }
> @@ -232,16 +235,21 @@ static int preallocate_pmds(struct mm_struct *mm, pmd_t *pmds[], int count)
>  		gfp &= ~__GFP_ACCOUNT;
>  
>  	for (i = 0; i < count; i++) {
> -		pmd_t *pmd = (pmd_t *)__get_free_page(gfp);
> -		if (!pmd)
> +		pmd_t *pmd = NULL;
> +		struct ptdesc *ptdesc = pagetable_alloc(gfp, 0);
> +
> +		if (!ptdesc)
>  			failed = true;
> -		if (pmd && !pgtable_pmd_page_ctor(virt_to_page(pmd))) {
> -			free_page((unsigned long)pmd);
> -			pmd = NULL;
> +		if (ptdesc && !pagetable_pmd_ctor(ptdesc)) {
> +			pagetable_free(ptdesc);
> +			ptdesc = NULL;
>  			failed = true;
>  		}
> -		if (pmd)
> +		if (ptdesc) {
>  			mm_inc_nr_pmds(mm);
> +			pmd = ptdesc_address(ptdesc);
> +		}
> +
>  		pmds[i] = pmd;
>  	}
>  
> @@ -830,7 +838,7 @@ int pud_free_pmd_page(pud_t *pud, unsigned long addr)
>  
>  	free_page((unsigned long)pmd_sv);
>  
> -	pgtable_pmd_page_dtor(virt_to_page(pmd));
> +	pagetable_pmd_dtor(virt_to_ptdesc(pmd));
>  	free_page((unsigned long)pmd);
>  
>  	return 1;
> -- 
> 2.40.1
> 
> 

-- 
Sincerely yours,
Mike.

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