1 files changed, 24 insertions, 27 deletions

diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
index e2c197fd4f9d..375d6285475e 100644
--- a/virt/kvm/coalesced_mmio.c
+++ b/virt/kvm/coalesced_mmio.c
@@ -40,27 +40,6 @@ static int coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev *dev,
 	return 1;
 }
 
-static int coalesced_mmio_has_room(struct kvm_coalesced_mmio_dev *dev, u32 last)
-{
-	struct kvm_coalesced_mmio_ring *ring;
-	unsigned avail;
-
-	/* Are we able to batch it ? */
-
-	/* last is the first free entry
-	 * check if we don't meet the first used entry
-	 * there is always one unused entry in the buffer
-	 */
-	ring = dev->kvm->coalesced_mmio_ring;
-	avail = (ring->first - last - 1) % KVM_COALESCED_MMIO_MAX;
-	if (avail == 0) {
-		/* full */
-		return 0;
-	}
-
-	return 1;
-}
-
 static int coalesced_mmio_write(struct kvm_vcpu *vcpu,
 				struct kvm_io_device *this, gpa_t addr,
 				int len, const void *val)
@@ -74,9 +53,15 @@ static int coalesced_mmio_write(struct kvm_vcpu *vcpu,
 
 	spin_lock(&dev->kvm->ring_lock);
 
+	/*
+	 * last is the index of the entry to fill.  Verify userspace hasn't
+	 * set last to be out of range, and that there is room in the ring.
+	 * Leave one entry free in the ring so that userspace can differentiate
+	 * between an empty ring and a full ring.
+	 */
 	insert = READ_ONCE(ring->last);
-	if (!coalesced_mmio_has_room(dev, insert) ||
-	    insert >= KVM_COALESCED_MMIO_MAX) {
+	if (insert >= KVM_COALESCED_MMIO_MAX ||
+	    (insert + 1) % KVM_COALESCED_MMIO_MAX == READ_ONCE(ring->first)) {
 		spin_unlock(&dev->kvm->ring_lock);
 		return -EOPNOTSUPP;
 	}
@@ -111,7 +96,7 @@ int kvm_coalesced_mmio_init(struct kvm *kvm)
 {
 	struct page *page;
 
-	page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+	page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
 	if (!page)
 		return -ENOMEM;
 
@@ -174,21 +159,33 @@ int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
 					   struct kvm_coalesced_mmio_zone *zone)
 {
 	struct kvm_coalesced_mmio_dev *dev, *tmp;
+	int r;
 
 	if (zone->pio != 1 && zone->pio != 0)
 		return -EINVAL;
 
 	mutex_lock(&kvm->slots_lock);
 
-	list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list)
+	list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list) {
 		if (zone->pio == dev->zone.pio &&
 		    coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
-			kvm_io_bus_unregister_dev(kvm,
+			r = kvm_io_bus_unregister_dev(kvm,
 				zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS, &dev->dev);
-			kvm_iodevice_destructor(&dev->dev);
+			/*
+			 * On failure, unregister destroys all devices on the
+			 * bus, including the target device. There's no need
+			 * to restart the walk as there aren't any zones left.
+			 */
+			if (r)
+				break;
 		}
+	}
 
 	mutex_unlock(&kvm->slots_lock);
 
+	/*
+	 * Ignore the result of kvm_io_bus_unregister_dev(), from userspace's
+	 * perspective, the coalesced MMIO is most definitely unregistered.
+	 */
 	return 0;
 }