KVM: stats: Add VM dirty_pages stats for the number of dirty pages

Add a generic VM stats dirty_pages to record the number of dirty pages
reflected in dirty_bitmap at the moment.

Original-by: Peter Feiner <pfeiner@google.com>
Signed-off-by: Jing Zhang <jingzhangos@google.com>

arch/powerpc/kvm/book3s_64_mmu_hv.c

@@ -1122,8 +1122,10 @@ long kvmppc_hv_get_dirty_log_hpt(struct kvm *kvm,
 		 * since we always put huge-page HPTEs in the rmap chain
 		 * corresponding to their page base address.
 		 */
-		if (npages)
+		if (npages) {
 			set_dirty_bits(map, i, npages);
+			kvm->stat.generic.dirty_pages += npages;
+		}
 		++rmapp;
 	}
 	preempt_enable();
@@ -1178,8 +1180,10 @@ void kvmppc_unpin_guest_page(struct kvm *kvm, void *va, unsigned long gpa,
 	gfn = gpa >> PAGE_SHIFT;
 	srcu_idx = srcu_read_lock(&kvm->srcu);
 	memslot = gfn_to_memslot(kvm, gfn);
-	if (memslot && memslot->dirty_bitmap)
+	if (memslot && memslot->dirty_bitmap) {
 		set_bit_le(gfn - memslot->base_gfn, memslot->dirty_bitmap);
+		++kvm->stat.generic.dirty_pages;
+	}
 	srcu_read_unlock(&kvm->srcu, srcu_idx);
 }
 

arch/powerpc/kvm/book3s_64_mmu_radix.c

@@ -1150,6 +1150,7 @@ long kvmppc_hv_get_dirty_log_radix(struct kvm *kvm,
 		j = i + 1;
 		if (npages) {
 			set_dirty_bits(map, i, npages);
+			kvm->stat.generic.dirty_pages += npages;
 			j = i + npages;
 		}
 	}

arch/powerpc/kvm/book3s_hv_rm_mmu.c

@@ -109,6 +109,7 @@ void kvmppc_update_dirty_map(const struct kvm_memory_slot *memslot,
 	npages = (psize + PAGE_SIZE - 1) / PAGE_SIZE;
 	gfn -= memslot->base_gfn;
 	set_dirty_bits_atomic(memslot->dirty_bitmap, gfn, npages);
+	kvm->stat.generic.dirty_pages += npages;
 }
 EXPORT_SYMBOL_GPL(kvmppc_update_dirty_map);
 

include/linux/kvm_host.h

@@ -1421,7 +1421,8 @@ struct _kvm_stats_desc {
 		KVM_STATS_BASE_POW10, -9)
 
 #define KVM_GENERIC_VM_STATS()						       \
-	STATS_DESC_COUNTER(VM_GENERIC, remote_tlb_flush)
+	STATS_DESC_COUNTER(VM_GENERIC, remote_tlb_flush),		       \
+	STATS_DESC_COUNTER(VM_GENERIC, dirty_pages)
 
 #define KVM_GENERIC_VCPU_STATS()					       \
 	STATS_DESC_COUNTER(VCPU_GENERIC, halt_successful_poll),		       \

include/linux/kvm_types.h

@@ -78,6 +78,7 @@ struct kvm_mmu_memory_cache {
 
 struct kvm_vm_stat_generic {
 	u64 remote_tlb_flush;
+	u64 dirty_pages;
 };
 
 struct kvm_vcpu_stat_generic {

virt/kvm/kvm_main.c

@@ -1228,6 +1228,19 @@ static int kvm_alloc_dirty_bitmap(struct kvm_memory_slot *memslot)
 	return 0;
 }
 
+static inline unsigned long hweight_dirty_bitmap(
+						struct kvm_memory_slot *memslot)
+{
+	unsigned long i;
+	unsigned long count = 0;
+	unsigned long n = kvm_dirty_bitmap_bytes(memslot);
+
+	for (i = 0; i < n / sizeof(long); ++i)
+		count += hweight_long(memslot->dirty_bitmap[i]);
+
+	return count;
+}
+
 /*
  * Delete a memslot by decrementing the number of used slots and shifting all
  * other entries in the array forward one spot.
@@ -1612,6 +1625,7 @@ static int kvm_delete_memslot(struct kvm *kvm,
 	if (r)
 		return r;
 
+	kvm->stat.generic.dirty_pages -= hweight_dirty_bitmap(old);
 	kvm_free_memslot(kvm, old);
 	return 0;
 }
@@ -1733,8 +1747,10 @@ int __kvm_set_memory_region(struct kvm *kvm,
 	if (r)
 		goto out_bitmap;
 
-	if (old.dirty_bitmap && !new.dirty_bitmap)
+	if (old.dirty_bitmap && !new.dirty_bitmap) {
+		kvm->stat.generic.dirty_pages -= hweight_dirty_bitmap(&old);
 		kvm_destroy_dirty_bitmap(&old);
+	}
 	return 0;
 
 out_bitmap:
@@ -1895,6 +1911,7 @@ static int kvm_get_dirty_log_protect(struct kvm *kvm, struct kvm_dirty_log *log)
 			offset = i * BITS_PER_LONG;
 			kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot,
 								offset, mask);
+			kvm->stat.generic.dirty_pages -= hweight_long(mask);
 		}
 		KVM_MMU_UNLOCK(kvm);
 	}
@@ -2012,6 +2029,7 @@ static int kvm_clear_dirty_log_protect(struct kvm *kvm,
 			flush = true;
 			kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot,
 								offset, mask);
+			kvm->stat.generic.dirty_pages -= hweight_long(mask);
 		}
 	}
 	KVM_MMU_UNLOCK(kvm);
@@ -3062,11 +3080,13 @@ void mark_page_dirty_in_slot(struct kvm *kvm,
 		unsigned long rel_gfn = gfn - memslot->base_gfn;
 		u32 slot = (memslot->as_id << 16) | memslot->id;
 
-		if (kvm->dirty_ring_size)
+		if (kvm->dirty_ring_size) {
 			kvm_dirty_ring_push(kvm_dirty_ring_get(kvm),
 					    slot, rel_gfn);
-		else
+		} else {
 			set_bit_le(rel_gfn, memslot->dirty_bitmap);
+			++kvm->stat.generic.dirty_pages;
+		}
 	}
 }
 EXPORT_SYMBOL_GPL(mark_page_dirty_in_slot);