hw/display: introduce virtio-dmabuf

This API manages objects (in this iteration,
dmabuf fds) that can be shared along different
virtio devices, associated to a UUID.

The API allows the different devices to add,
remove and/or retrieve the objects by simply
invoking the public functions that reside in the
virtio-dmabuf file.

For vhost backends, the API stores the pointer
to the backend holding the object.

Suggested-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Albert Esteve <aesteve@redhat.com>
Message-Id: <20231002065706.94707-3-aesteve@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

2 files changed, 139 insertions, 0 deletions

diff --git a/hw/display/meson.build b/hw/display/meson.build
index 413ba4a..05619c6 100644
--- a/hw/display/meson.build
+++ b/hw/display/meson.build
@@ -37,6 +37,7 @@ system_ss.add(when: 'CONFIG_MACFB', if_true: files('macfb.c'))
 system_ss.add(when: 'CONFIG_NEXTCUBE', if_true: files('next-fb.c'))
 
 system_ss.add(when: 'CONFIG_VGA', if_true: files('vga.c'))
+system_ss.add(when: 'CONFIG_VIRTIO', if_true: files('virtio-dmabuf.c'))
 
 if (config_all_devices.has_key('CONFIG_VGA_CIRRUS') or
     config_all_devices.has_key('CONFIG_VGA_PCI') or
diff --git a/hw/display/virtio-dmabuf.c b/hw/display/virtio-dmabuf.c
new file mode 100644
index 0000000..4a8e430
--- /dev/null
+++ b/hw/display/virtio-dmabuf.c
@@ -0,0 +1,138 @@
+/*
+ * Virtio Shared dma-buf
+ *
+ * Copyright Red Hat, Inc. 2023
+ *
+ * Authors:
+ *     Albert Esteve <aesteve@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+
+#include "hw/virtio/virtio-dmabuf.h"
+
+
+static GMutex lock;
+static GHashTable *resource_uuids;
+
+/*
+ * uuid_equal_func: wrapper for UUID is_equal function to
+ * satisfy g_hash_table_new expected parameters signatures.
+ */
+static int uuid_equal_func(const void *lhv, const void *rhv)
+{
+    return qemu_uuid_is_equal(lhv, rhv);
+}
+
+static bool virtio_add_resource(QemuUUID *uuid, VirtioSharedObject *value)
+{
+    bool result = false;
+
+    g_mutex_lock(&lock);
+    if (resource_uuids == NULL) {
+        resource_uuids = g_hash_table_new_full(qemu_uuid_hash,
+                                               uuid_equal_func,
+                                               NULL,
+                                               g_free);
+    }
+    if (g_hash_table_lookup(resource_uuids, uuid) == NULL) {
+        result = g_hash_table_insert(resource_uuids, uuid, value);
+    }
+    g_mutex_unlock(&lock);
+
+    return result;
+}
+
+bool virtio_add_dmabuf(QemuUUID *uuid, int udmabuf_fd)
+{
+    bool result;
+    VirtioSharedObject *vso;
+    if (udmabuf_fd < 0) {
+        return false;
+    }
+    vso = g_new(VirtioSharedObject, 1);
+    vso->type = TYPE_DMABUF;
+    vso->value = GINT_TO_POINTER(udmabuf_fd);
+    result = virtio_add_resource(uuid, vso);
+
+    return result;
+}
+
+bool virtio_add_vhost_device(QemuUUID *uuid, struct vhost_dev *dev)
+{
+    bool result;
+    VirtioSharedObject *vso;
+    if (dev == NULL) {
+        return false;
+    }
+    vso = g_new(VirtioSharedObject, 1);
+    vso->type = TYPE_VHOST_DEV;
+    vso->value = dev;
+    result = virtio_add_resource(uuid, vso);
+
+    return result;
+}
+
+bool virtio_remove_resource(const QemuUUID *uuid)
+{
+    bool result;
+    g_mutex_lock(&lock);
+    result = g_hash_table_remove(resource_uuids, uuid);
+    g_mutex_unlock(&lock);
+
+    return result;
+}
+
+static VirtioSharedObject *get_shared_object(const QemuUUID *uuid)
+{
+    gpointer lookup_res = NULL;
+
+    g_mutex_lock(&lock);
+    if (resource_uuids != NULL) {
+        lookup_res = g_hash_table_lookup(resource_uuids, uuid);
+    }
+    g_mutex_unlock(&lock);
+
+    return (VirtioSharedObject *) lookup_res;
+}
+
+int virtio_lookup_dmabuf(const QemuUUID *uuid)
+{
+    VirtioSharedObject *vso = get_shared_object(uuid);
+    if (vso == NULL) {
+        return -1;
+    }
+    assert(vso->type == TYPE_DMABUF);
+    return GPOINTER_TO_INT(vso->value);
+}
+
+struct vhost_dev *virtio_lookup_vhost_device(const QemuUUID *uuid)
+{
+    VirtioSharedObject *vso = get_shared_object(uuid);
+    if (vso == NULL) {
+        return NULL;
+    }
+    assert(vso->type == TYPE_VHOST_DEV);
+    return (struct vhost_dev *) vso->value;
+}
+
+SharedObjectType virtio_object_type(const QemuUUID *uuid)
+{
+    VirtioSharedObject *vso = get_shared_object(uuid);
+    if (vso == NULL) {
+        return TYPE_INVALID;
+    }
+    return vso->type;
+}
+
+void virtio_free_resources(void)
+{
+    g_mutex_lock(&lock);
+    g_hash_table_destroy(resource_uuids);
+    /* Reference count shall be 0 after the implicit unref on destroy */
+    resource_uuids = NULL;
+    g_mutex_unlock(&lock);
+}