Re: [PATCH v3 01/11] KVM: MMU: rename has_wrprotected_page to mmu_gfn_lpage_is_disallowed

[Paolo Bonzini]

On 14/02/2016 12:31, Xiao Guangrong wrote:
> kvm_lpage_info->write_count is used to detect if the large page mapping
> for the gfn on the specified level is allowed, rename it to disallow_lpage
> to reflect its purpose, also we rename has_wrprotected_page() to
> mmu_gfn_lpage_is_disallowed() to make the code more clearer
> 
> Later we will extend this mechanism for page tracking: if the gfn is
> tracked then large mapping for that gfn on any level is not allowed.
> The new name is more straightforward
> 
> Signed-off-by: Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx>
> ---
>  Documentation/virtual/kvm/mmu.txt |  6 +++---
>  arch/x86/include/asm/kvm_host.h   |  2 +-
>  arch/x86/kvm/mmu.c                | 25 +++++++++++++------------
>  arch/x86/kvm/x86.c                | 14 ++++++++------
>  4 files changed, 25 insertions(+), 22 deletions(-)
> 
> diff --git a/Documentation/virtual/kvm/mmu.txt b/Documentation/virtual/kvm/mmu.txt
> index daf9c0f..dda2e93 100644
> --- a/Documentation/virtual/kvm/mmu.txt
> +++ b/Documentation/virtual/kvm/mmu.txt
> @@ -391,11 +391,11 @@ To instantiate a large spte, four constraints must be satisfied:
>    write-protected pages
>  - the guest page must be wholly contained by a single memory slot
>  
> -To check the last two conditions, the mmu maintains a ->write_count set of
> +To check the last two conditions, the mmu maintains a ->disallow_lpage set of
>  arrays for each memory slot and large page size.  Every write protected page
> -causes its write_count to be incremented, thus preventing instantiation of
> +causes its disallow_lpage to be incremented, thus preventing instantiation of
>  a large spte.  The frames at the end of an unaligned memory slot have
> -artificially inflated ->write_counts so they can never be instantiated.
> +artificially inflated ->disallow_lpages so they can never be instantiated.
>  
>  Zapping all pages (page generation count)
>  =========================================
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 7dd6d55..e1c1f57 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -644,7 +644,7 @@ struct kvm_vcpu_arch {
>  };
>  
>  struct kvm_lpage_info {
> -	int write_count;
> +	int disallow_lpage;
>  };
>  
>  struct kvm_arch_memory_slot {
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 95a955d..de9e992 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -789,7 +789,7 @@ static void account_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
>  	slot = __gfn_to_memslot(slots, gfn);
>  	for (i = PT_DIRECTORY_LEVEL; i <= PT_MAX_HUGEPAGE_LEVEL; ++i) {
>  		linfo = lpage_info_slot(gfn, slot, i);
> -		linfo->write_count += 1;
> +		linfo->disallow_lpage += 1;
>  	}
>  	kvm->arch.indirect_shadow_pages++;
>  }
> @@ -807,31 +807,32 @@ static void unaccount_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
>  	slot = __gfn_to_memslot(slots, gfn);
>  	for (i = PT_DIRECTORY_LEVEL; i <= PT_MAX_HUGEPAGE_LEVEL; ++i) {
>  		linfo = lpage_info_slot(gfn, slot, i);
> -		linfo->write_count -= 1;
> -		WARN_ON(linfo->write_count < 0);
> +		linfo->disallow_lpage -= 1;
> +		WARN_ON(linfo->disallow_lpage < 0);
>  	}
>  	kvm->arch.indirect_shadow_pages--;
>  }
>  
> -static int __has_wrprotected_page(gfn_t gfn, int level,
> -				  struct kvm_memory_slot *slot)
> +static bool __mmu_gfn_lpage_is_disallowed(gfn_t gfn, int level,
> +					  struct kvm_memory_slot *slot)
>  {
>  	struct kvm_lpage_info *linfo;
>  
>  	if (slot) {
>  		linfo = lpage_info_slot(gfn, slot, level);
> -		return linfo->write_count;
> +		return !!linfo->disallow_lpage;
>  	}
>  
> -	return 1;
> +	return true;
>  }
>  
> -static int has_wrprotected_page(struct kvm_vcpu *vcpu, gfn_t gfn, int level)
> +static bool mmu_gfn_lpage_is_disallowed(struct kvm_vcpu *vcpu, gfn_t gfn,
> +					int level)
>  {
>  	struct kvm_memory_slot *slot;
>  
>  	slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
> -	return __has_wrprotected_page(gfn, level, slot);
> +	return __mmu_gfn_lpage_is_disallowed(gfn, level, slot);
>  }
>  
>  static int host_mapping_level(struct kvm *kvm, gfn_t gfn)
> @@ -897,7 +898,7 @@ static int mapping_level(struct kvm_vcpu *vcpu, gfn_t large_gfn,
>  	max_level = min(kvm_x86_ops->get_lpage_level(), host_level);
>  
>  	for (level = PT_DIRECTORY_LEVEL; level <= max_level; ++level)
> -		if (__has_wrprotected_page(large_gfn, level, slot))
> +		if (__mmu_gfn_lpage_is_disallowed(large_gfn, level, slot))
>  			break;
>  
>  	return level - 1;
> @@ -2503,7 +2504,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
>  		 * be fixed if guest refault.
>  		 */
>  		if (level > PT_PAGE_TABLE_LEVEL &&
> -		    has_wrprotected_page(vcpu, gfn, level))
> +		    mmu_gfn_lpage_is_disallowed(vcpu, gfn, level))
>  			goto done;
>  
>  		spte |= PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE;
> @@ -2768,7 +2769,7 @@ static void transparent_hugepage_adjust(struct kvm_vcpu *vcpu,
>  	if (!is_error_noslot_pfn(pfn) && !kvm_is_reserved_pfn(pfn) &&
>  	    level == PT_PAGE_TABLE_LEVEL &&
>  	    PageTransCompound(pfn_to_page(pfn)) &&
> -	    !has_wrprotected_page(vcpu, gfn, PT_DIRECTORY_LEVEL)) {
> +	    !mmu_gfn_lpage_is_disallowed(vcpu, gfn, PT_DIRECTORY_LEVEL)) {
>  		unsigned long mask;
>  		/*
>  		 * mmu_notifier_retry was successful and we hold the
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index cf15bc5..f448e64 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7903,6 +7903,7 @@ int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
>  	int i;
>  
>  	for (i = 0; i < KVM_NR_PAGE_SIZES; ++i) {
> +		struct kvm_lpage_info *linfo;
>  		unsigned long ugfn;
>  		int lpages;
>  		int level = i + 1;
> @@ -7917,15 +7918,16 @@ int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
>  		if (i == 0)
>  			continue;
>  
> -		slot->arch.lpage_info[i - 1] = kvm_kvzalloc(lpages *
> -					sizeof(*slot->arch.lpage_info[i - 1]));
> -		if (!slot->arch.lpage_info[i - 1])
> +		linfo = kvm_kvzalloc(lpages * sizeof(*linfo));
> +		if (!linfo)
>  			goto out_free;
>  
> +		slot->arch.lpage_info[i - 1] = linfo;
> +
>  		if (slot->base_gfn & (KVM_PAGES_PER_HPAGE(level) - 1))
> -			slot->arch.lpage_info[i - 1][0].write_count = 1;
> +			linfo[0].disallow_lpage = 1;
>  		if ((slot->base_gfn + npages) & (KVM_PAGES_PER_HPAGE(level) - 1))
> -			slot->arch.lpage_info[i - 1][lpages - 1].write_count = 1;
> +			linfo[lpages - 1].disallow_lpage = 1;
>  		ugfn = slot->userspace_addr >> PAGE_SHIFT;
>  		/*
>  		 * If the gfn and userspace address are not aligned wrt each
> @@ -7937,7 +7939,7 @@ int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
>  			unsigned long j;
>  
>  			for (j = 0; j < lpages; ++j)
> -				slot->arch.lpage_info[i - 1][j].write_count = 1;
> +				linfo[j].disallow_lpage = 1;
>  		}
>  	}
>  
> 

Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>