Subject: Re: [PATCH] KVM: ARM: Remove pgtable page standard functions from stage-2 page tables

From: Yu Zhao <[email-masked]>
Date: Mon, 11 Mar 2019 20:40:29 -0600

On Tue, Mar 12, 2019 at 07:49:02AM +0530, Anshuman Khandual wrote:
> ARM64 standard pgtable functions are going to use pgtable_page_[ctor|dtor]
> or pgtable_pmd_page_[ctor|dtor] constructs. At present KVM guest stage-2
> PUD|PMD|PTE level page tabe pages are allocated with __get_free_page()
> via mmu_memory_cache_alloc() but released with standard pud|pmd_free() or
> pte_free_kernel(). These will fail once they start calling into pgtable_
> [pmd]_page_dtor() for pages which never originally went through respective
> constructor functions. Hence convert all stage-2 page table page release
> functions to call buddy directly while freeing pages.

This is apparently cleaner than what I have done.

Acked-by: Yu Zhao <[email-masked]>

> Signed-off-by: Anshuman Khandual <[email-masked]>
> ---
>  arch/arm/include/asm/stage2_pgtable.h   | 4 ++--
>  arch/arm64/include/asm/stage2_pgtable.h | 4 ++--
>  virt/kvm/arm/mmu.c                      | 2 +-
>  3 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm/include/asm/stage2_pgtable.h b/arch/arm/include/asm/stage2_pgtable.h
> index de2089501b8b..417a3be00718 100644
> --- a/arch/arm/include/asm/stage2_pgtable.h
> +++ b/arch/arm/include/asm/stage2_pgtable.h
> @@ -32,14 +32,14 @@
>  #define stage2_pgd_present(kvm, pgd)		pgd_present(pgd)
>  #define stage2_pgd_populate(kvm, pgd, pud)	pgd_populate(NULL, pgd, pud)
>  #define stage2_pud_offset(kvm, pgd, address)	pud_offset(pgd, address)
> -#define stage2_pud_free(kvm, pud)		pud_free(NULL, pud)
> +#define stage2_pud_free(kvm, pud)		free_page((unsigned long)pud)
>  
>  #define stage2_pud_none(kvm, pud)		pud_none(pud)
>  #define stage2_pud_clear(kvm, pud)		pud_clear(pud)
>  #define stage2_pud_present(kvm, pud)		pud_present(pud)
>  #define stage2_pud_populate(kvm, pud, pmd)	pud_populate(NULL, pud, pmd)
>  #define stage2_pmd_offset(kvm, pud, address)	pmd_offset(pud, address)
> -#define stage2_pmd_free(kvm, pmd)		pmd_free(NULL, pmd)
> +#define stage2_pmd_free(kvm, pmd)		free_page((unsigned long)pmd)
>  
>  #define stage2_pud_huge(kvm, pud)		pud_huge(pud)
>  
> diff --git a/arch/arm64/include/asm/stage2_pgtable.h b/arch/arm64/include/asm/stage2_pgtable.h
> index 5412fa40825e..915809e4ac32 100644
> --- a/arch/arm64/include/asm/stage2_pgtable.h
> +++ b/arch/arm64/include/asm/stage2_pgtable.h
> @@ -119,7 +119,7 @@ static inline pud_t *stage2_pud_offset(struct kvm *kvm,
>  static inline void stage2_pud_free(struct kvm *kvm, pud_t *pud)
>  {
>  	if (kvm_stage2_has_pud(kvm))
> -		pud_free(NULL, pud);
> +		free_page((unsigned long)pud);
>  }
>  
>  static inline bool stage2_pud_table_empty(struct kvm *kvm, pud_t *pudp)
> @@ -192,7 +192,7 @@ static inline pmd_t *stage2_pmd_offset(struct kvm *kvm,
>  static inline void stage2_pmd_free(struct kvm *kvm, pmd_t *pmd)
>  {
>  	if (kvm_stage2_has_pmd(kvm))
> -		pmd_free(NULL, pmd);
> +		free_page((unsigned long)pmd);
>  }
>  
>  static inline bool stage2_pud_huge(struct kvm *kvm, pud_t pud)
> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
> index e9d28a7ca673..00bd79a2f0b1 100644
> --- a/virt/kvm/arm/mmu.c
> +++ b/virt/kvm/arm/mmu.c
> @@ -191,7 +191,7 @@ static void clear_stage2_pmd_entry(struct kvm *kvm, pmd_t *pmd, phys_addr_t addr
>  	VM_BUG_ON(pmd_thp_or_huge(*pmd));
>  	pmd_clear(pmd);
>  	kvm_tlb_flush_vmid_ipa(kvm, addr);
> -	pte_free_kernel(NULL, pte_table);
> +	__free_page(virt_to_page(pte_table));
>  	put_page(virt_to_page(pmd));
>  }
>  
> -- 
> 2.20.1
> 

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