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>
Signed-off-by: Albert Esteve <aesteve@redhat.com>
---
 MAINTAINERS                       |   7 ++
 hw/display/meson.build            |   1 +
 hw/display/virtio-dmabuf.c        | 136 +++++++++++++++++++++++++++++
 include/hw/virtio/virtio-dmabuf.h | 103 ++++++++++++++++++++++
 tests/unit/meson.build            |   1 +
 tests/unit/test-virtio-dmabuf.c   | 137 ++++++++++++++++++++++++++++++
 6 files changed, 385 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 3b29568ed4..fb0f7b823f 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..7e7a536c4d
--- /dev/null
+++ b/hw/display/virtio-dmabuf.c
@@ -0,0 +1,136 @@
+/*
+ * 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, 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);
+}
diff --git a/include/hw/virtio/virtio-dmabuf.h b/include/hw/virtio/virtio-dmabuf.h
new file mode 100644
index 0000000000..202eec5868
--- /dev/null
+++ b/include/hw/virtio/virtio-dmabuf.h
@@ -0,0 +1,103 @@
+/*
+ * 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"
+#include "vhost.h"
+
+typedef enum SharedObjectType {
+    TYPE_INVALID = 0,
+    TYPE_DMABUF,
+    TYPE_VHOST_DEV,
+} SharedObjectType;
+
+typedef struct VirtioSharedObject {
+    SharedObjectType type;
+    gpointer value;
+} VirtioSharedObject;
+
+/**
+ * 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_add_vhost_device() - Add a new exporter vhost device that holds the
+ * resource with the associated UUID
+ * @uuid: new resource's UUID
+ * @dev: the pointer to the vhost device that holds the resource. The caller
+ *       retains ownership over the device struct and its lifecycle.
+ *
+ * Return: true if the UUID did not exist and the device has been tracked,
+ * 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_vhost_device(QemuUUID *uuid, struct vhost_dev *dev);
+
+/**
+ * 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_lookup_vhost_device() - Looks for an exporter vhost device in the
+ * lookup table
+ * @uuid: resource's UUID
+ *
+ * Return: pointer to the vhost_dev struct, or NULL if the key is not found.
+ */
+struct vhost_dev *virtio_lookup_vhost_device(const QemuUUID *uuid);
+
+/**
+ * virtio_object_type() - Looks for the type of resource in the lookup table
+ * @uuid: resource's UUID
+ *
+ * Return: the type of resource associated with the UUID, or TYPE_INVALID if
+ * the key is not found.
+ */
+SharedObjectType virtio_object_type(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..a45ec52f42
--- /dev/null
+++ b/tests/unit/test-virtio-dmabuf.c
@@ -0,0 +1,137 @@
+/*
+ * 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_add_remove_dev(void)
+{
+    QemuUUID uuid;
+    struct vhost_dev *dev = g_new0(struct vhost_dev, 1);
+    int i;
+
+    for (i = 0; i < 100; ++i) {
+        qemu_uuid_generate(&uuid);
+        virtio_add_vhost_device(&uuid, dev);
+        /* vhost device is found */
+        g_assert(virtio_lookup_vhost_device(&uuid) != NULL);
+        /* Remove the vhost device */
+        g_assert(virtio_remove_resource(&uuid));
+        /* vhost device is not found anymore */
+        g_assert(virtio_lookup_vhost_device(&uuid) == NULL);
+    }
+    g_free(dev);
+}
+
+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;
+    struct vhost_dev *dev = NULL;
+    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);
+        /* Add a new vhost device with invalid (NULL) pointer */
+        g_assert_false(virtio_add_vhost_device(&uuid, dev));
+        /* vhost device is not found */
+        g_assert(virtio_lookup_vhost_device(&uuid) == NULL);
+    }
+
+    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/add_rm_dev", test_add_remove_dev);
+    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();
+}
-- 
2.41.0

On 7/9/23 09:43, Albert Esteve wrote:
> 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>
> Signed-off-by: Albert Esteve <aesteve@redhat.com>
> ---
>   MAINTAINERS                       |   7 ++
>   hw/display/meson.build            |   1 +
>   hw/display/virtio-dmabuf.c        | 136 +++++++++++++++++++++++++++++
>   include/hw/virtio/virtio-dmabuf.h | 103 ++++++++++++++++++++++
>   tests/unit/meson.build            |   1 +
>   tests/unit/test-virtio-dmabuf.c   | 137 ++++++++++++++++++++++++++++++
>   6 files changed, 385 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/include/hw/virtio/virtio-dmabuf.h b/include/hw/virtio/virtio-dmabuf.h
> new file mode 100644
> index 0000000000..202eec5868
> --- /dev/null
> +++ b/include/hw/virtio/virtio-dmabuf.h
> @@ -0,0 +1,103 @@
> +/*
> + * 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"

See https://www.qemu.org/docs/master/devel/style.html#include-directives

   Do not include “qemu/osdep.h” from header files since the .c
   file will have already included it.

> +#include <glib.h>

This one is also included via "qemu/osdep.h" -> "glib-compat.h"

> +#include "qemu/uuid.h"
> +#include "vhost.h"
> +
> +typedef enum SharedObjectType {
> +    TYPE_INVALID = 0,
> +    TYPE_DMABUF,
> +    TYPE_VHOST_DEV,
> +} SharedObjectType;
> +
> +typedef struct VirtioSharedObject {
> +    SharedObjectType type;
> +    gpointer value;
> +} VirtioSharedObject;

Since this need a repost, better use "hw/display: Introduce 
virtio-dmabuf" as patch subject (and "util/uuid" prefix for the previous 
patch).

Otherwise LGTM, so with these changes:

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

On Thu, Sep 7, 2023 at 10:19 AM Philippe Mathieu-Daudé <philmd@linaro.org>
wrote:

> On 7/9/23 09:43, Albert Esteve wrote:
> > 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>
> > Signed-off-by: Albert Esteve <aesteve@redhat.com>
> > ---
> >   MAINTAINERS                       |   7 ++
> >   hw/display/meson.build            |   1 +
> >   hw/display/virtio-dmabuf.c        | 136 +++++++++++++++++++++++++++++
> >   include/hw/virtio/virtio-dmabuf.h | 103 ++++++++++++++++++++++
> >   tests/unit/meson.build            |   1 +
> >   tests/unit/test-virtio-dmabuf.c   | 137 ++++++++++++++++++++++++++++++
> >   6 files changed, 385 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/include/hw/virtio/virtio-dmabuf.h
> b/include/hw/virtio/virtio-dmabuf.h
> > new file mode 100644
> > index 0000000000..202eec5868
> > --- /dev/null
> > +++ b/include/hw/virtio/virtio-dmabuf.h
> > @@ -0,0 +1,103 @@
> > +/*
> > + * 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"
>
> See https://www.qemu.org/docs/master/devel/style.html#include-directives
>
>    Do not include “qemu/osdep.h” from header files since the .c
>    file will have already included it.
>
> > +#include <glib.h>
>
> This one is also included via "qemu/osdep.h" -> "glib-compat.h"
>
> > +#include "qemu/uuid.h"
> > +#include "vhost.h"
> > +
> > +typedef enum SharedObjectType {
> > +    TYPE_INVALID = 0,
> > +    TYPE_DMABUF,
> > +    TYPE_VHOST_DEV,
> > +} SharedObjectType;
> > +
> > +typedef struct VirtioSharedObject {
> > +    SharedObjectType type;
> > +    gpointer value;
> > +} VirtioSharedObject;
>
> Since this need a repost, better use "hw/display: Introduce
> virtio-dmabuf" as patch subject (and "util/uuid" prefix for the previous
> patch).
>
> Otherwise LGTM, so with these changes:
>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>
>
Thanks a lot! I'll do it for the next review.
Any other comment on the other commits?