[PATCH v4 2/4] virtio-dmabuf: introduce virtio-dmabuf

[Albert Esteve <aesteve@redhat.com>]

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

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.

Suggested-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Albert Esteve <aesteve@redhat.com>
---
 MAINTAINERS                       |   7 ++
 hw/display/meson.build            |   1 +
 hw/display/virtio-dmabuf.c        |  90 ++++++++++++++++++++++++
 include/hw/virtio/virtio-dmabuf.h |  59 ++++++++++++++++
 tests/unit/meson.build            |   1 +
 tests/unit/test-virtio-dmabuf.c   | 112 ++++++++++++++++++++++++++++++
 6 files changed, 270 insertions(+)
 create mode 100644 hw/display/virtio-dmabuf.c
 create mode 100644 include/hw/virtio/virtio-dmabuf.h
 create mode 100644 tests/unit/test-virtio-dmabuf.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 7f323cd2eb..ce77a691a1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2150,6 +2150,13 @@ T: git https://gitlab.com/cohuck/qemu.git s390-next
 T: git https://github.com/borntraeger/qemu.git s390-next
 L: qemu-s390x@nongnu.org
 
+virtio-dmabuf
+M: Albert Esteve <aesteve@redhat.com>
+S: Supported
+F: hw/display/virtio-dmabuf.c
+F: include/hw/virtio/virtio-dmabuf.h
+F: tests/unit/test-virtio-dmabuf.c
+
 virtiofs
 M: Stefan Hajnoczi <stefanha@redhat.com>
 S: Supported
diff --git a/hw/display/meson.build b/hw/display/meson.build
index 413ba4ab24..05619c6968 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 0000000000..7dba0b2c71
--- /dev/null
+++ b/hw/display/virtio-dmabuf.c
@@ -0,0 +1,90 @@
+/*
+ * 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 "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, gpointer value)
+{
+    assert(resource_uuids != NULL);
+    if (g_hash_table_lookup(resource_uuids, uuid) != NULL) {
+        return false;
+    }
+
+    return g_hash_table_insert(resource_uuids, uuid, value);
+}
+
+static gpointer virtio_lookup_resource(const QemuUUID *uuid)
+{
+    if (resource_uuids == NULL) {
+        return NULL;
+    }
+
+    return g_hash_table_lookup(resource_uuids, uuid);
+}
+
+bool virtio_add_dmabuf(QemuUUID *uuid, int udmabuf_fd)
+{
+    bool result;
+    if (udmabuf_fd < 0) {
+        return false;
+    }
+    g_mutex_lock(&lock);
+    if (resource_uuids == NULL) {
+        resource_uuids = g_hash_table_new(qemu_uuid_hash, uuid_equal_func);
+    }
+    result = virtio_add_resource(uuid, GINT_TO_POINTER(udmabuf_fd));
+    g_mutex_unlock(&lock);
+
+    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;
+}
+
+int virtio_lookup_dmabuf(const QemuUUID *uuid)
+{
+    g_mutex_lock(&lock);
+    gpointer lookup_res = virtio_lookup_resource(uuid);
+    g_mutex_unlock(&lock);
+    if (lookup_res == NULL) {
+        return -1;
+    }
+
+    return GPOINTER_TO_INT(lookup_res);
+}
+
+void virtio_free_resources(void)
+{
+    g_hash_table_destroy(resource_uuids);
+    /* Reference count shall be 0 after the implicit unref on destroy */
+    resource_uuids = NULL;
+}
diff --git a/include/hw/virtio/virtio-dmabuf.h b/include/hw/virtio/virtio-dmabuf.h
new file mode 100644
index 0000000000..4fdd394c4b
--- /dev/null
+++ b/include/hw/virtio/virtio-dmabuf.h
@@ -0,0 +1,59 @@
+/*
+ * 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.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef VIRTIO_DMABUF_H
+#define VIRTIO_DMABUF_H
+
+#include "qemu/osdep.h"
+
+#include <glib.h>
+#include "qemu/uuid.h"
+
+/**
+ * virtio_add_dmabuf() - Add a new dma-buf resource to the lookup table
+ * @uuid: new resource's UUID
+ * @dmabuf_fd: the dma-buf descriptor that will be stored and shared with
+ *             other virtio devices. The caller retains ownership over the
+ *             descriptor and its lifecycle.
+ *
+ * Note: @dmabuf_fd must be a valid (non-negative) file descriptor.
+ *
+ * Return: true if the UUID did not exist and the resource has been added,
+ * false if another resource with the same UUID already existed.
+ * Note that if it finds a repeated UUID, the resource is not inserted in
+ * the lookup table.
+ */
+bool virtio_add_dmabuf(QemuUUID *uuid, int dmabuf_fd);
+
+/**
+ * virtio_remove_resource() - Removes a resource from the lookup table
+ * @uuid: resource's UUID
+ *
+ * Return: true if the UUID has been found and removed from the lookup table.
+ */
+bool virtio_remove_resource(const QemuUUID *uuid);
+
+/**
+ * virtio_lookup_dmabuf() - Looks for a dma-buf resource in the lookup table
+ * @uuid: resource's UUID
+ *
+ * Return: the dma-buf file descriptor integer, or -1 if the key is not found.
+ */
+int virtio_lookup_dmabuf(const QemuUUID *uuid);
+
+/**
+ * virtio_free_resources() - Destroys all keys and values of the shared
+ * resources lookup table, and frees them
+ */
+void virtio_free_resources(void);
+
+#endif /* VIRTIO_DMABUF_H */
diff --git a/tests/unit/meson.build b/tests/unit/meson.build
index 93977cc32d..425ecc30fb 100644
--- a/tests/unit/meson.build
+++ b/tests/unit/meson.build
@@ -50,6 +50,7 @@ tests = {
   'test-qapi-util': [],
   'test-interval-tree': [],
   'test-xs-node': [qom],
+  'test-virtio-dmabuf': [meson.project_source_root() / 'hw/display/virtio-dmabuf.c'],
 }
 
 if have_system or have_tools
diff --git a/tests/unit/test-virtio-dmabuf.c b/tests/unit/test-virtio-dmabuf.c
new file mode 100644
index 0000000000..53436aa93d
--- /dev/null
+++ b/tests/unit/test-virtio-dmabuf.c
@@ -0,0 +1,112 @@
+/*
+ * QEMU tests for shared dma-buf API
+ *
+ * Copyright (c) 2023 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "hw/virtio/virtio-dmabuf.h"
+
+
+static void test_add_remove_resources(void)
+{
+    QemuUUID uuid;
+    int i, dmabuf_fd;
+
+    for (i = 0; i < 100; ++i) {
+        qemu_uuid_generate(&uuid);
+        dmabuf_fd = g_random_int_range(3, 500);
+        /* Add a new resource */
+        g_assert(virtio_add_dmabuf(&uuid, dmabuf_fd));
+        g_assert_cmpint(virtio_lookup_dmabuf(&uuid), ==, dmabuf_fd);
+        /* Remove the resource */
+        g_assert(virtio_remove_resource(&uuid));
+        /* Resource is not found anymore */
+        g_assert_cmpint(virtio_lookup_dmabuf(&uuid), ==, -1);
+    }
+}
+
+static void test_remove_invalid_resource(void)
+{
+    QemuUUID uuid;
+    int i;
+
+    for (i = 0; i < 20; ++i) {
+        qemu_uuid_generate(&uuid);
+        g_assert_cmpint(virtio_lookup_dmabuf(&uuid), ==, -1);
+        /* Removing a resource that does not exist returns false */
+        g_assert_false(virtio_remove_resource(&uuid));
+    }
+}
+
+static void test_add_invalid_resource(void)
+{
+    QemuUUID uuid;
+    int i, dmabuf_fd = -2, alt_dmabuf = 2;
+
+    for (i = 0; i < 20; ++i) {
+        qemu_uuid_generate(&uuid);
+        /* Add a new resource with invalid (negative) resource fd */
+        g_assert_false(virtio_add_dmabuf(&uuid, dmabuf_fd));
+        /* Resource is not found */
+        g_assert_cmpint(virtio_lookup_dmabuf(&uuid), ==, -1);
+    }
+
+    for (i = 0; i < 20; ++i) {
+        /* Add a valid resource */
+        qemu_uuid_generate(&uuid);
+        dmabuf_fd = g_random_int_range(3, 500);
+        g_assert(virtio_add_dmabuf(&uuid, dmabuf_fd));
+        g_assert_cmpint(virtio_lookup_dmabuf(&uuid), ==, dmabuf_fd);
+        /* Add a new resource with repeated uuid returns false */
+        g_assert_false(virtio_add_dmabuf(&uuid, alt_dmabuf));
+        /* The value for the uuid key is not replaced */
+        g_assert_cmpint(virtio_lookup_dmabuf(&uuid), ==, dmabuf_fd);
+    }
+}
+
+static void test_free_resources(void)
+{
+    QemuUUID uuids[20];
+    int i, dmabuf_fd;
+
+    for (i = 0; i < ARRAY_SIZE(uuids); ++i) {
+        qemu_uuid_generate(&uuids[i]);
+        dmabuf_fd = g_random_int_range(3, 500);
+        g_assert(virtio_add_dmabuf(&uuids[i], dmabuf_fd));
+        g_assert_cmpint(virtio_lookup_dmabuf(&uuids[i]), ==, dmabuf_fd);
+    }
+    virtio_free_resources();
+    for (i = 0; i < ARRAY_SIZE(uuids); ++i) {
+        /* None of the resources is found after free'd */
+        g_assert_cmpint(virtio_lookup_dmabuf(&uuids[i]), ==, -1);
+    }
+
+}
+
+int main(int argc, char **argv)
+{
+    g_test_init(&argc, &argv, NULL);
+    g_test_add_func("/virtio-dmabuf/add_rm_res", test_add_remove_resources);
+    g_test_add_func("/virtio-dmabuf/rm_invalid_res",
+                    test_remove_invalid_resource);
+    g_test_add_func("/virtio-dmabuf/add_invalid_res",
+                    test_add_invalid_resource);
+    g_test_add_func("/virtio-dmabuf/free_res", test_free_resources);
+
+    return g_test_run();
+}
-- 
2.40.0