[PATCH v4 11/21] KVM: arm64: Convert page-aging and access faults to generic page-table API

[Alexandru Elisei]

Hi Will,

On 9/7/20 4:23 PM, Will Deacon wrote:
> Convert the page-aging functions and access fault handler to use the
> generic page-table code instead of walking the page-table directly.
>
> Cc: Marc Zyngier <maz at kernel.org>
> Cc: Quentin Perret <qperret at google.com>
> Reviewed-by: Gavin Shan <gshan at redhat.com>
> Signed-off-by: Will Deacon <will at kernel.org>
> ---
>  arch/arm64/kvm/mmu.c | 74 ++++++++++----------------------------------
>  1 file changed, 16 insertions(+), 58 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index a7021509231c..a036aac3ed24 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1703,46 +1703,23 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  	return ret;
>  }
>  
> -/*
> - * Resolve the access fault by making the page young again.
> - * Note that because the faulting entry is guaranteed not to be
> - * cached in the TLB, we don't need to invalidate anything.
> - * Only the HW Access Flag updates are supported for Stage 2 (no DBM),
> - * so there is no need for atomic (pte|pmd)_mkyoung operations.
> - */
> +/* Resolve the access fault by making the page young again. */
>  static void handle_access_fault(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
>  {
> -	pud_t *pud;
> -	pmd_t *pmd;
> -	pte_t *pte;
> -	kvm_pfn_t pfn;
> -	bool pfn_valid = false;
> +	pte_t pte;
> +	kvm_pte_t kpte;
> +	struct kvm_s2_mmu *mmu;
>  
>  	trace_kvm_access_fault(fault_ipa);
>  
>  	spin_lock(&vcpu->kvm->mmu_lock);
> -
> -	if (!stage2_get_leaf_entry(vcpu->arch.hw_mmu, fault_ipa, &pud, &pmd, &pte))
> -		goto out;
> -
> -	if (pud) {		/* HugeTLB */
> -		*pud = kvm_s2pud_mkyoung(*pud);
> -		pfn = kvm_pud_pfn(*pud);
> -		pfn_valid = true;
> -	} else	if (pmd) {	/* THP, HugeTLB */
> -		*pmd = pmd_mkyoung(*pmd);
> -		pfn = pmd_pfn(*pmd);
> -		pfn_valid = true;
> -	} else {
> -		*pte = pte_mkyoung(*pte);	/* Just a page... */
> -		pfn = pte_pfn(*pte);
> -		pfn_valid = true;
> -	}
> -
> -out:
> +	mmu = vcpu->arch.hw_mmu;
> +	kpte = kvm_pgtable_stage2_mkyoung(mmu->pgt, fault_ipa);
>  	spin_unlock(&vcpu->kvm->mmu_lock);
> -	if (pfn_valid)
> -		kvm_set_pfn_accessed(pfn);
> +
> +	pte = __pte(kpte);
> +	if (pte_valid(pte))
> +		kvm_set_pfn_accessed(pte_pfn(pte));
>  }
>  
>  /**
> @@ -1959,38 +1936,19 @@ int 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;
> +	pte_t pte;
> +	kvm_pte_t kpte;
>  
>  	WARN_ON(size != PAGE_SIZE && size != PMD_SIZE && size != PUD_SIZE);
> -	if (!stage2_get_leaf_entry(&kvm->arch.mmu, gpa, &pud, &pmd, &pte))
> -		return 0;
> -
> -	if (pud)
> -		return stage2_pudp_test_and_clear_young(pud);
> -	else if (pmd)
> -		return stage2_pmdp_test_and_clear_young(pmd);
> -	else
> -		return stage2_ptep_test_and_clear_young(pte);
> +	kpte = kvm_pgtable_stage2_mkold(kvm->arch.mmu.pgt, gpa);
> +	pte = __pte(kpte);
> +	return pte_valid(pte) && pte_young(pte);

I checked that the semantics of the return value are preserved. The old version of
the function returned 1 if stage2_get_leaf_entry() returned true (entry was found
and it was valid) and the entry was young, which is equivalent to pte_valid(pte)
&& pte_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 && size != PUD_SIZE);
> -	if (!stage2_get_leaf_entry(&kvm->arch.mmu, gpa, &pud, &pmd, &pte))
> -		return 0;
> -
> -	if (pud)
> -		return kvm_s2pud_young(*pud);
> -	else if (pmd)
> -		return pmd_young(*pmd);
> -	else
> -		return pte_young(*pte);
> +	return kvm_pgtable_stage2_is_young(kvm->arch.mmu.pgt, gpa);
>  }

Reviewed-by: Alexandru Elisei <alexandru.elisei at arm.com>

Thanks,
Alex
>  
>  int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end)