linux-kernel - Re: [PATCH v9 7/8] KVM: arm64: Update age handlers to support PUD hugepages

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Date:   Mon, 3 Dec 2018 20:49:30 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Punit Agrawal <punit.agrawal@....com>, kvmarm@...ts.cs.columbia.edu
Cc:     suzuki.poulose@....com, marc.zyngier@....com,
        Catalin Marinas <catalin.marinas@....com>, will.deacon@....com,
        linux-kernel@...r.kernel.org,
        Christoffer Dall <christoffer.dall@....com>,
        punitagrawal@...il.com, Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v9 7/8] KVM: arm64: Update age handlers to support PUD
 hugepages



On 10/31/2018 11:27 PM, Punit Agrawal wrote:
> In preparation for creating larger hugepages at Stage 2, add support
> to the age handling notifiers for PUD hugepages when encountered.
> 
> Provide trivial helpers for arm32 to allow sharing code.
> 
> Signed-off-by: Punit Agrawal <punit.agrawal@....com>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
> Cc: Christoffer Dall <christoffer.dall@....com>
> Cc: Marc Zyngier <marc.zyngier@....com>
> Cc: Russell King <linux@...linux.org.uk>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> ---
>  arch/arm/include/asm/kvm_mmu.h   |  6 +++++
>  arch/arm64/include/asm/kvm_mmu.h |  5 ++++
>  arch/arm64/include/asm/pgtable.h |  1 +
>  virt/kvm/arm/mmu.c               | 39 ++++++++++++++++----------------
>  4 files changed, 32 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
> index fea5e723e3ac..e62f0913ce7d 100644
> --- a/arch/arm/include/asm/kvm_mmu.h
> +++ b/arch/arm/include/asm/kvm_mmu.h
> @@ -117,6 +117,12 @@ static inline pud_t kvm_s2pud_mkyoung(pud_t pud)
>  	return pud;
>  }
>  
> +static inline bool kvm_s2pud_young(pud_t pud)
> +{
> +	BUG();
> +	return false;
> +}
> +
>  static inline pte_t kvm_s2pte_mkwrite(pte_t pte)
>  {
>  	pte_val(pte) |= L_PTE_S2_RDWR;
> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> index 612032bbb428..9f941f70775c 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -273,6 +273,11 @@ static inline pud_t kvm_s2pud_mkyoung(pud_t pud)
>  	return pud_mkyoung(pud);
>  }
>  
> +static inline bool kvm_s2pud_young(pud_t pud)
> +{
> +	return pud_young(pud);
> +}
> +
>  #define hyp_pte_table_empty(ptep) kvm_page_empty(ptep)
>  
>  #ifdef __PAGETABLE_PMD_FOLDED
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index f51e2271e6a3..bb0f3f17a7a9 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -386,6 +386,7 @@ static inline int pmd_protnone(pmd_t pmd)
>  #define pfn_pmd(pfn,prot)	__pmd(__phys_to_pmd_val((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
>  #define mk_pmd(page,prot)	pfn_pmd(page_to_pfn(page),prot)
>  
> +#define pud_young(pud)		pte_young(pud_pte(pud))
>  #define pud_mkyoung(pud)	pte_pud(pte_mkyoung(pud_pte(pud)))
>  #define pud_write(pud)		pte_write(pud_pte(pud))
>  
> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
> index bd749601195f..3893ea6a50bf 100644
> --- a/virt/kvm/arm/mmu.c
> +++ b/virt/kvm/arm/mmu.c
> @@ -1225,6 +1225,11 @@ static int stage2_pmdp_test_and_clear_young(pmd_t *pmd)
>  	return stage2_ptep_test_and_clear_young((pte_t *)pmd);
>  }
>  
> +static int stage2_pudp_test_and_clear_young(pud_t *pud)
> +{
> +	return stage2_ptep_test_and_clear_young((pte_t *)pud);
> +}
> +
>  /**
>   * kvm_phys_addr_ioremap - map a device range to guest IPA
>   *
> @@ -1932,42 +1937,38 @@ void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
>  
>  static int kvm_age_hva_handler(struct kvm *kvm, gpa_t gpa, u64 size, void *data)
>  {
> +	pud_t *pud;
>  	pmd_t *pmd;
>  	pte_t *pte;
>  
> -	WARN_ON(size != PAGE_SIZE && size != PMD_SIZE);
> -	pmd = stage2_get_pmd(kvm, NULL, gpa);
> -	if (!pmd || pmd_none(*pmd))	/* Nothing there */
> +	WARN_ON(size != PAGE_SIZE && size != PMD_SIZE && size != PUD_SIZE);
> +	if (!stage2_get_leaf_entry(kvm, gpa, &pud, &pmd, &pte))
>  		return 0;
>  
> -	if (pmd_thp_or_huge(*pmd))	/* THP, HugeTLB */
> +	if (pud)
> +		return stage2_pudp_test_and_clear_young(pud);
> +	else if (pmd)
>  		return stage2_pmdp_test_and_clear_young(pmd);
> -
> -	pte = pte_offset_kernel(pmd, gpa);
> -	if (pte_none(*pte))
> -		return 0;
> -
> -	return stage2_ptep_test_and_clear_young(pte);
> +	else
> +		return stage2_ptep_test_and_clear_young(pte);
>  }
>  
>  static int kvm_test_age_hva_handler(struct kvm *kvm, gpa_t gpa, u64 size, void *data)
>  {
> +	pud_t *pud;
>  	pmd_t *pmd;
>  	pte_t *pte;
>  
> -	WARN_ON(size != PAGE_SIZE && size != PMD_SIZE);
> -	pmd = stage2_get_pmd(kvm, NULL, gpa);
> -	if (!pmd || pmd_none(*pmd))	/* Nothing there */
> +	WARN_ON(size != PAGE_SIZE && size != PMD_SIZE && size != PUD_SIZE);
> +	if (!stage2_get_leaf_entry(kvm, gpa, &pud, &pmd, &pte))
>  		return 0;
>  
> -	if (pmd_thp_or_huge(*pmd))		/* THP, HugeTLB */
> +	if (pud)
> +		return kvm_s2pud_young(*pud);
> +	else if (pmd)
>  		return pmd_young(*pmd);
> -
> -	pte = pte_offset_kernel(pmd, gpa);
> -	if (!pte_none(*pte))		/* Just a page... */
> +	else
>  		return pte_young(*pte);
> -
> -	return 0;
>  }
>  
>  int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end)
> 

If stage2_get_leaf_entry() is avoided (which it should be) some of the previous
patches can be folded into just a single one like defining new HW page table
definitions, arm32 trivial functions and PUD specific additions at various
stage 2 page table walkers etc.