KVM: use SRCU for dirty log
Marcelo Tosatti [Wed, 23 Dec 2009 16:35:22 +0000 (14:35 -0200)]
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/x86.c

index 43da65f..e748835 100644 (file)
@@ -2415,27 +2415,60 @@ static int kvm_vm_ioctl_reinject(struct kvm *kvm,
 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 = NULL;
 
        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);
+
+       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) {
+               struct kvm_memslots *slots, *old_slots;
+
                spin_lock(&kvm->mmu_lock);
                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);
+
+               slots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
+               if (!slots)
+                       goto out_free;
+
+               memcpy(slots, kvm->memslots, sizeof(struct kvm_memslots));
+               slots->memslots[log->slot].dirty_bitmap = dirty_bitmap;
+
+               old_slots = kvm->memslots;
+               rcu_assign_pointer(kvm->memslots, slots);
+               synchronize_srcu_expedited(&kvm->srcu);
+               dirty_bitmap = old_slots->memslots[log->slot].dirty_bitmap;
+               kfree(old_slots);
        }
+
        r = 0;
+       if (copy_to_user(log->dirty_bitmap, dirty_bitmap, n))
+               r = -EFAULT;
+out_free:
+       vfree(dirty_bitmap);
 out:
        up_write(&kvm->slots_lock);
        return r;