Subject: [PATCH v9 4/4] arm: ARMv7 dirty page logging 2nd stage page fault handling support

From: [email-masked] (Christoffer Dall)
Date: Mon, 11 Aug 2014 21:13:15 +0200

On Thu, Jul 24, 2014 at 05:56:08PM -0700, Mario Smarduch wrote:
> This patch adds support for handling 2nd stage page faults during migration,
> it disables faulting in huge pages, and dissolves huge pages to page tables.
> In case migration is canceled huge pages will be used again.
> 
> Signed-off-by: Mario Smarduch <[email-masked]>
> ---
>  arch/arm/kvm/mmu.c |   31 +++++++++++++++++++++++++------
>  1 file changed, 25 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index ca84331..a17812a 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -642,7 +642,8 @@ static int stage2_set_pmd_huge(struct kvm *kvm, struct kvm_mmu_memory_cache
>  }
>  
>  static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
> -			  phys_addr_t addr, const pte_t *new_pte, bool iomap)
> +			  phys_addr_t addr, const pte_t *new_pte, bool iomap,
> +			  bool logging_active)
>  {
>  	pmd_t *pmd;
>  	pte_t *pte, old_pte;
> @@ -657,6 +658,15 @@ static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
>  		return 0;
>  	}
>  
> +	/*
> +	 * While dirty memory logging, clear PMD entry for huge page and split
> +	 * into smaller pages, to track dirty memory at page granularity.
> +	 */
> +	if (logging_active && kvm_pmd_huge(*pmd)) {
> +		phys_addr_t ipa = pmd_pfn(*pmd) << PAGE_SHIFT;
> +		clear_pmd_entry(kvm, pmd, ipa);

clear_pmd_entry has a VM_BUG_ON(kvm_pmd_huge(*pmd)) so that is
definitely not the right thing to call.

> +	}
> +
>  	/* Create stage-2 page mappings - Level 2 */
>  	if (pmd_none(*pmd)) {
>  		if (!cache)
> @@ -709,7 +719,7 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
>  		if (ret)
>  			goto out;
>  		spin_lock(&kvm->mmu_lock);
> -		ret = stage2_set_pte(kvm, &cache, addr, &pte, true);
> +		ret = stage2_set_pte(kvm, &cache, addr, &pte, true, false);
>  		spin_unlock(&kvm->mmu_lock);
>  		if (ret)
>  			goto out;
> @@ -926,6 +936,12 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  	struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
>  	struct vm_area_struct *vma;
>  	pfn_t pfn;
> +	/* Get logging status, if dirty_bitmap is not NULL then logging is on */
> +	#ifdef CONFIG_ARM
> +		bool logging_active = !!memslot->dirty_bitmap;
> +	#else
> +		bool logging_active = false;
> +	#endif

can you make this an inline in the header files for now please?

>  
>  	write_fault = kvm_is_write_fault(kvm_vcpu_get_hsr(vcpu));
>  	if (fault_status == FSC_PERM && !write_fault) {
> @@ -936,7 +952,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  	/* Let's check if we will get back a huge page backed by hugetlbfs */
>  	down_read(&current->mm->mmap_sem);
>  	vma = find_vma_intersection(current->mm, hva, hva + 1);
> -	if (is_vm_hugetlb_page(vma)) {
> +	if (is_vm_hugetlb_page(vma) && !logging_active) {
>  		hugetlb = true;
>  		gfn = (fault_ipa & PMD_MASK) >> PAGE_SHIFT;
>  	} else {
> @@ -979,7 +995,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  	spin_lock(&kvm->mmu_lock);
>  	if (mmu_notifier_retry(kvm, mmu_seq))
>  		goto out_unlock;
> -	if (!hugetlb && !force_pte)
> +	if (!hugetlb && !force_pte && !logging_active)
>  		hugetlb = transparent_hugepage_adjust(&pfn, &fault_ipa);
>  
>  	if (hugetlb) {
> @@ -998,9 +1014,12 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  			kvm_set_pfn_dirty(pfn);
>  		}
>  		coherent_cache_guest_page(vcpu, hva, PAGE_SIZE);
> -		ret = stage2_set_pte(kvm, memcache, fault_ipa, &new_pte, false);
> +		ret = stage2_set_pte(kvm, memcache, fault_ipa, &new_pte, false,
> +					logging_active);
>  	}
>  
> +	if (write_fault)
> +		mark_page_dirty(kvm, gfn);
>  
>  out_unlock:
>  	spin_unlock(&kvm->mmu_lock);
> @@ -1151,7 +1170,7 @@ static void kvm_set_spte_handler(struct kvm *kvm, gpa_t gpa, void *data)
>  {
>  	pte_t *pte = (pte_t *)data;
>  
> -	stage2_set_pte(kvm, NULL, gpa, pte, false);
> +	stage2_set_pte(kvm, NULL, gpa, pte, false, false);

why is logging never active if we are called from MMU notifiers?

>  }
> -- 
> 1.7.9.5

Thanks,
-Christoffer