KVM: switch coalesced mmio changes to slots_lock

switch coalesced mmio slots_lock.  slots_lock is already taken for read
everywhere, so we only need to take it for write when changing zones.
This is in preparation to removing in_range and kvm->lock around it.

[avi: fix build]

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

virt/kvm/coalesced_mmio.c

diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
index 397f419..b40946c 100644
--- a/virt/kvm/coalesced_mmio.c
+++ b/virt/kvm/coalesced_mmio.c
@@ -115,16 +115,16 @@
 	if (dev == NULL)
 		return -EINVAL;
 
-	mutex_lock(&kvm->lock);
+	down_write(&kvm->slots_lock);
 	if (dev->nb_zones >= KVM_COALESCED_MMIO_ZONE_MAX) {
-		mutex_unlock(&kvm->lock);
+		up_write(&kvm->slots_lock);
 		return -ENOBUFS;
 	}
 
 	dev->zone[dev->nb_zones] = *zone;
 	dev->nb_zones++;
 
-	mutex_unlock(&kvm->lock);
+	up_write(&kvm->slots_lock);
 	return 0;
 }
 
@@ -138,7 +138,7 @@
 	if (dev == NULL)
 		return -EINVAL;
 
-	mutex_lock(&kvm->lock);
+	down_write(&kvm->slots_lock);
 
 	i = dev->nb_zones;
 	while(i) {
@@ -156,7 +156,7 @@
 		i--;
 	}
 
-	mutex_unlock(&kvm->lock);
+	up_write(&kvm->slots_lock);
 
 	return 0;
 }