vdpa_sim: make IOTLB entries limit configurable

Some devices may require a higher limit for the number of IOTLB
entries, so let's make it configurable through a module parameter.

By default, it's initialized with the current limit (2048).
Suggested-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/r/20201215144256.155342-5-sgarzare@redhat.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/vdpa_sim/vdpa_sim.c

@@ -31,6 +31,11 @@ static int batch_mapping = 1;
 module_param(batch_mapping, int, 0444);
 MODULE_PARM_DESC(batch_mapping, "Batched mapping 1 -Enable; 0 - Disable");
 
+static int max_iotlb_entries = 2048;
+module_param(max_iotlb_entries, int, 0444);
+MODULE_PARM_DESC(max_iotlb_entries,
+		 "Maximum number of iotlb entries. 0 means unlimited. (default: 2048)");
+
 static char *macaddr;
 module_param(macaddr, charp, 0);
 MODULE_PARM_DESC(macaddr, "Ethernet MAC address");
@@ -371,7 +376,7 @@ static struct vdpasim *vdpasim_create(void)
 	if (!vdpasim->vqs)
 		goto err_iommu;
 
-	vdpasim->iommu = vhost_iotlb_alloc(2048, 0);
+	vdpasim->iommu = vhost_iotlb_alloc(max_iotlb_entries, 0);
 	if (!vdpasim->iommu)
 		goto err_iommu;