[patch 03/10] KVM: switch dirty_log to mmu_lock protection

[Marcelo Tosatti <mtosatti@xxxxxxxxxx>]

get_dirty_log vs mark_page_dirty need to be mutually exclusive. Switch
to mmu_lock protection.

Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>

Index: kvm-slotslock/arch/x86/kvm/paging_tmpl.h
===================================================================
--- kvm-slotslock.orig/arch/x86/kvm/paging_tmpl.h
+++ kvm-slotslock/arch/x86/kvm/paging_tmpl.h
@@ -175,7 +175,9 @@ walk:
 		if (!(pte & PT_ACCESSED_MASK)) {
 			trace_kvm_mmu_set_accessed_bit(table_gfn, index,
 						       sizeof(pte));
+			spin_lock(&vcpu->kvm->mmu_lock);
 			mark_page_dirty(vcpu->kvm, table_gfn);
+			spin_unlock(&vcpu->kvm->mmu_lock);
 			if (FNAME(cmpxchg_gpte)(vcpu->kvm, table_gfn,
 			    index, pte, pte|PT_ACCESSED_MASK))
 				goto walk;
@@ -215,7 +217,9 @@ walk:
 		bool ret;
 
 		trace_kvm_mmu_set_dirty_bit(table_gfn, index, sizeof(pte));
+		spin_lock(&vcpu->kvm->mmu_lock);
 		mark_page_dirty(vcpu->kvm, table_gfn);
+		spin_unlock(&vcpu->kvm->mmu_lock);
 		ret = FNAME(cmpxchg_gpte)(vcpu->kvm, table_gfn, index, pte,
 			    pte|PT_DIRTY_MASK);
 		if (ret)
Index: kvm-slotslock/arch/x86/kvm/x86.c
===================================================================
--- kvm-slotslock.orig/arch/x86/kvm/x86.c
+++ kvm-slotslock/arch/x86/kvm/x86.c
@@ -692,7 +692,9 @@ static void kvm_write_guest_time(struct 
 
 	kunmap_atomic(shared_kaddr, KM_USER0);
 
+	spin_lock(&v->kvm->mmu_lock);
 	mark_page_dirty(v->kvm, vcpu->time >> PAGE_SHIFT);
+	spin_unlock(&v->kvm->mmu_lock);
 }
 
 static int kvm_request_guest_time_update(struct kvm_vcpu *v)
@@ -2147,27 +2149,45 @@ static int kvm_vm_ioctl_reinject(struct 
 int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 				      struct kvm_dirty_log *log)
 {
-	int r;
-	int n;
+	int r, n, i;
 	struct kvm_memory_slot *memslot;
-	int is_dirty = 0;
+	unsigned long is_dirty = 0;
+	unsigned long *dirty_bitmap;
 
 	down_write(&kvm->slots_lock);
 
-	r = kvm_get_dirty_log(kvm, log, &is_dirty);
-	if (r)
+	r = -EINVAL;
+	if (log->slot >= KVM_MEMORY_SLOTS)
+		goto out;
+
+	memslot = &kvm->memslots->memslots[log->slot];
+	r = -ENOENT;
+	if (!memslot->dirty_bitmap)
+		goto out;
+
+	n = ALIGN(memslot->npages, BITS_PER_LONG) / 8;
+	r = -ENOMEM;
+	dirty_bitmap = vmalloc(n);
+	if (!dirty_bitmap)
 		goto out;
+	memset(dirty_bitmap, 0, n);
+
+	spin_lock(&kvm->mmu_lock);
+	for (i = 0; !is_dirty && i < n/sizeof(long); ++i)
+		is_dirty = memslot->dirty_bitmap[i];
 
 	/* If nothing is dirty, don't bother messing with page tables. */
 	if (is_dirty) {
-		spin_lock(&kvm->mmu_lock);
+		memcpy(dirty_bitmap, memslot->dirty_bitmap, n);
+		memset(memslot->dirty_bitmap, 0, n);
 		kvm_mmu_slot_remove_write_access(kvm, log->slot);
-		spin_unlock(&kvm->mmu_lock);
 		memslot = &kvm->memslots->memslots[log->slot];
-		n = ALIGN(memslot->npages, BITS_PER_LONG) / 8;
-		memset(memslot->dirty_bitmap, 0, n);
 	}
+	spin_unlock(&kvm->mmu_lock);
+
 	r = 0;
+	if (copy_to_user(log->dirty_bitmap, dirty_bitmap, n))
+		r = -EFAULT;
 out:
 	up_write(&kvm->slots_lock);
 	return r;
@@ -3491,7 +3511,9 @@ static void vapic_exit(struct kvm_vcpu *
 
 	down_read(&vcpu->kvm->slots_lock);
 	kvm_release_page_dirty(apic->vapic_page);
+	spin_lock(&vcpu->kvm->mmu_lock);
 	mark_page_dirty(vcpu->kvm, apic->vapic_addr >> PAGE_SHIFT);
+	spin_unlock(&vcpu->kvm->mmu_lock);
 	up_read(&vcpu->kvm->slots_lock);
 }
 
Index: kvm-slotslock/virt/kvm/kvm_main.c
===================================================================
--- kvm-slotslock.orig/virt/kvm/kvm_main.c
+++ kvm-slotslock/virt/kvm/kvm_main.c
@@ -1007,7 +1007,9 @@ int kvm_write_guest_page(struct kvm *kvm
 	r = copy_to_user((void __user *)addr + offset, data, len);
 	if (r)
 		return -EFAULT;
+	spin_lock(&kvm->mmu_lock);
 	mark_page_dirty(kvm, gfn);
+	spin_unlock(&kvm->mmu_lock);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(kvm_write_guest_page);


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