vfio: Create VFIOAddressSpace objects as needed

So far, VFIO has a notion of different logical DMA address spaces, but
only ever uses one (system memory).  This patch extends this, creating
new VFIOAddressSpace objects as necessary, according to the AddressSpace
reported by the PCI subsystem for this device's DMAs.

This isn't enough yet to support guest side IOMMUs with VFIO, but it does
mean we could now support VFIO devices on, for example, a guest side PCI
host bridge which maps system memory at somewhere other than 0 in PCI
space.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

hw/misc/vfio.c

@@ -139,13 +139,8 @@ typedef struct VFIOAddressSpace {
     QLIST_ENTRY(VFIOAddressSpace) list;
 } VFIOAddressSpace;
 
-static VFIOAddressSpace vfio_address_space_memory;
-
-static void vfio_address_space_init(VFIOAddressSpace *space, AddressSpace *as)
-{
-    space->as = as;
-    QLIST_INIT(&space->containers);
-}
+static QLIST_HEAD(, VFIOAddressSpace) vfio_address_spaces =
+    QLIST_HEAD_INITIALIZER(vfio_address_spaces);
 
 struct VFIOGroup;
 
@@ -3433,13 +3428,41 @@ static void vfio_kvm_device_del_group(VFIOGroup *group)
 #endif
 }
 
+static VFIOAddressSpace *vfio_get_address_space(AddressSpace *as)
+{
+    VFIOAddressSpace *space;
+
+    QLIST_FOREACH(space, &vfio_address_spaces, list) {
+        if (space->as == as) {
+            return space;
+        }
+    }
+
+    /* No suitable VFIOAddressSpace, create a new one */
+    space = g_malloc0(sizeof(*space));
+    space->as = as;
+    QLIST_INIT(&space->containers);
+
+    QLIST_INSERT_HEAD(&vfio_address_spaces, space, list);
+
+    return space;
+}
+
+static void vfio_put_address_space(VFIOAddressSpace *space)
+{
+    if (QLIST_EMPTY(&space->containers)) {
+        QLIST_REMOVE(space, list);
+        g_free(space);
+    }
+}
+
 static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
 {
     VFIOContainer *container;
     int ret, fd;
     VFIOAddressSpace *space;
 
-    space = &vfio_address_space_memory;
+    space = vfio_get_address_space(as);
 
     QLIST_FOREACH(container, &space->containers, next) {
         if (!ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &container->fd)) {
@@ -3452,7 +3475,8 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
     fd = qemu_open("/dev/vfio/vfio", O_RDWR);
     if (fd < 0) {
         error_report("vfio: failed to open /dev/vfio/vfio: %m");
-        return -errno;
+        ret = -errno;
+        goto put_space_exit;
     }
 
     ret = ioctl(fd, VFIO_GET_API_VERSION);
@@ -3519,6 +3543,9 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
 close_fd_exit:
     close(fd);
 
+put_space_exit:
+    vfio_put_address_space(space);
+
     return ret;
 }
 
@@ -3535,13 +3562,17 @@ static void vfio_disconnect_container(VFIOGroup *group)
     group->container = NULL;
 
     if (QLIST_EMPTY(&container->group_list)) {
+        VFIOAddressSpace *space = container->space;
+
         if (container->iommu_data.release) {
             container->iommu_data.release(container);
         }
         QLIST_REMOVE(container, next);
         DPRINTF("vfio_disconnect_container: close container->fd\n");
         close(container->fd);
         g_free(container);
+
+        vfio_put_address_space(space);
     }
 }
 
@@ -3940,12 +3971,7 @@ static int vfio_initfn(PCIDevice *pdev)
     DPRINTF("%s(%04x:%02x:%02x.%x) group %d\n", __func__, vdev->host.domain,
             vdev->host.bus, vdev->host.slot, vdev->host.function, groupid);
 
-    if (pci_device_iommu_address_space(pdev) != &address_space_memory) {
-        error_report("vfio: DMA address space must be system memory");
-        return -EINVAL;
-    }
-
-    group = vfio_get_group(groupid, &address_space_memory);
+    group = vfio_get_group(groupid, pci_device_iommu_address_space(pdev));
     if (!group) {
         error_report("vfio: failed to get group %d", groupid);
         return -ENOENT;
@@ -4159,7 +4185,6 @@ static const TypeInfo vfio_pci_dev_info = {
 
 static void register_vfio_pci_dev_type(void)
 {
-    vfio_address_space_init(&vfio_address_space_memory, &address_space_memory);
     type_register_static(&vfio_pci_dev_info);
 }