[v2,4/6] vfio: support getting VFIOGroup from groupfd

Commit Message

Tiwei Bie March 19, 2018, 7:15 a.m. UTC

Add an API to support getting VFIOGroup from groupfd. When
groupfd is shared by another process, the VFIOGroup may not
have its container and address space in QEMU.

Besides, add a reference counter to better support getting
VFIOGroup multiple times.

Signed-off-by: Tiwei Bie <[e-mail]>
---
 hw/vfio/common.c              | 97 ++++++++++++++++++++++++++++++++++++++++++-
 include/hw/vfio/vfio-common.h |  2 +
 2 files changed, 98 insertions(+), 1 deletion(-)

Patch

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 5e84716218..24ec0f2c8d 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -1038,6 +1038,11 @@  static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
     int ret, fd;
     VFIOAddressSpace *space;
 
+    if (as == NULL) {
+        vfio_kvm_device_add_group(group);
+        return 0;
+    }
+
     space = vfio_get_address_space(as);
 
     QLIST_FOREACH(container, &space->containers, next) {
@@ -1237,6 +1242,10 @@  static void vfio_disconnect_container(VFIOGroup *group)
 {
     VFIOContainer *container = group->container;
 
+    if (container == NULL) {
+        return;
+    }
+
     QLIST_REMOVE(group, container_next);
     group->container = NULL;
 
@@ -1275,6 +1284,86 @@  static void vfio_disconnect_container(VFIOGroup *group)
     }
 }
 
+static int vfio_groupfd_to_groupid(int groupfd)
+{
+    char linkname[PATH_MAX];
+    char pathname[PATH_MAX];
+    char *filename;
+    int groupid, len;
+
+    snprintf(linkname, sizeof(linkname), "/proc/self/fd/%d", groupfd);
+
+    len = readlink(linkname, pathname, sizeof(pathname));
+    if (len <= 0 || len >= sizeof(pathname)) {
+        return -1;
+    }
+    pathname[len] = '\0';
+
+    filename = g_path_get_basename(pathname);
+    groupid = atoi(filename);
+    g_free(filename);
+
+    return groupid;
+}
+
+/*
+ * The @as param could be NULL. In this case, groupfd is shared by
+ * another process which will setup the DMA mapping for this group,
+ * and this group won't have container and address space in QEMU.
+ */
+VFIOGroup *vfio_get_group_from_fd(int groupfd, AddressSpace *as, Error **errp)
+{
+    VFIOGroup *group;
+    int groupid;
+
+    groupid = vfio_groupfd_to_groupid(groupfd);
+    if (groupid < 0) {
+        return NULL;
+    }
+
+    QLIST_FOREACH(group, &vfio_group_list, next) {
+        if (group->groupid == groupid) {
+            /* Found it.  Now is it already in the right context? */
+            if ((group->container == NULL && as == NULL) ||
+                (group->container && group->container->space->as == as)) {
+                    group->refcnt++;
+                    return group;
+            }
+            error_setg(errp, "group %d used in multiple address spaces",
+                       group->groupid);
+            return NULL;
+        }
+    }
+
+    group = g_malloc0(sizeof(*group));
+
+    group->fd = groupfd;
+    group->groupid = groupid;
+    group->refcnt = 1;
+
+    QLIST_INIT(&group->device_list);
+
+    if (vfio_connect_container(group, as, errp)) {
+        error_prepend(errp, "failed to setup container for group %d: ",
+                      groupid);
+        goto free_group_exit;
+    }
+
+    if (QLIST_EMPTY(&vfio_group_list)) {
+        qemu_register_reset(vfio_reset_handler, NULL);
+    }
+
+    QLIST_INSERT_HEAD(&vfio_group_list, group, next);
+
+    return group;
+
+free_group_exit:
+    g_free(group);
+
+    return NULL;
+}
+
+/* The @as param cannot be NULL. */
 VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp)
 {
     VFIOGroup *group;
@@ -1284,7 +1373,8 @@  VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp)
     QLIST_FOREACH(group, &vfio_group_list, next) {
         if (group->groupid == groupid) {
             /* Found it.  Now is it already in the right context? */
-            if (group->container->space->as == as) {
+            if (group->container && group->container->space->as == as) {
+                group->refcnt++;
                 return group;
             } else {
                 error_setg(errp, "group %d used in multiple address spaces",
@@ -1317,6 +1407,7 @@  VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp)
     }
 
     group->groupid = groupid;
+    group->refcnt = 1;
     QLIST_INIT(&group->device_list);
 
     if (vfio_connect_container(group, as, errp)) {
@@ -1348,6 +1439,10 @@  void vfio_put_group(VFIOGroup *group)
         return;
     }
 
+    if (--group->refcnt > 0) {
+        return;
+    }
+
     vfio_kvm_device_del_group(group);
     vfio_disconnect_container(group);
     QLIST_REMOVE(group, next);
diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index d9360148e6..b820f7984c 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -137,6 +137,7 @@  struct VFIODeviceOps {
 typedef struct VFIOGroup {
     int fd;
     int groupid;
+    int refcnt;
     VFIOContainer *container;
     QLIST_HEAD(, VFIODevice) device_list;
     QLIST_ENTRY(VFIOGroup) next;
@@ -180,6 +181,7 @@  void vfio_region_exit(VFIORegion *region);
 void vfio_region_finalize(VFIORegion *region);
 void vfio_reset_handler(void *opaque);
 VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp);
+VFIOGroup *vfio_get_group_from_fd(int groupfd, AddressSpace *as, Error **errp);
 void vfio_put_group(VFIOGroup *group);
 int vfio_get_device(VFIOGroup *group, const char *name,
                     VFIODevice *vbasedev, Error **errp);