[PATCH v7 0/4] Virtio shared dma-buf

[PATCH v7 0/4] Virtio shared dma-buf

[Albert Esteve]

v1 link -> https://lists.gnu.org/archive/html/qemu-devel/2023-05/msg00598.html
v2 link -> https://lists.gnu.org/archive/html/qemu-devel/2023-05/msg04530.html
v3 link -> https://lists.gnu.org/archive/html/qemu-devel/2023-05/msg06126.html
v4 link -> https://lists.gnu.org/archive/html/qemu-devel/2023-06/msg05174.html
v5 link -> https://lists.gnu.org/archive/html/qemu-devel/2023-08/msg00255.html
v6 link -> https://lists.gnu.org/archive/html/qemu-devel/2023-09/msg00987.html
v6 -> v7:
- Small refactor of a couple of virtio-dmabuf.c functions
- Add Error propagation for vhost_user_send_resp function
- Split last commit for vhost-user and libvhost-user

This patch covers the required steps to add support for virtio cross-device resource sharing[1],
which support is already available in the kernel.

The main usecase will be sharing dma buffers from virtio-gpu devices (as the exporter
-see VIRTIO_GPU_CMD_RESOURCE_ASSIGN_UUID in [2]), to virtio-video (under discussion)
devices (as the buffer-user or importer). Therefore, even though virtio specs talk about
resources or objects[3], this patch adds the infrastructure with dma-bufs in mind.
Note that virtio specs let the devices themselves define what a vitio object is.

These are the main parts that are covered in the patch:

- Add hash function to uuid module
- Shared resources table, to hold all resources that can be shared in the host and their assigned UUID,
  or pointers to the backend holding the resource
- Internal shared table API for virtio devices to add, lookup and remove resources
- Unit test to verify the API
- New messages to the vhost-user protocol to allow backend to interact with the shared
  table API through the control socket
- New vhost-user feature bit to enable shared objects feature

Applies cleanly to c152379422a204109f34ca2b43ecc538c7d738ae

[1] - https://lwn.net/Articles/828988/
[2] - https://docs.oasis-open.org/virtio/virtio/v1.2/csd01/virtio-v1.2-csd01.html#x1-3730006
[3] - https://docs.oasis-open.org/virtio/virtio/v1.2/csd01/virtio-v1.2-csd01.html#x1-10500011

Albert Esteve (4):
  uuid: add a hash function
  virtio-dmabuf: introduce virtio-dmabuf
  vhost-user: add shared_object msg
  libvhost-user: handle shared_object msg

 MAINTAINERS                               |   7 +
 docs/interop/vhost-user.rst               |  57 ++++++++
 hw/display/meson.build                    |   1 +
 hw/display/virtio-dmabuf.c                | 136 ++++++++++++++++++
 hw/virtio/vhost-user.c                    | 168 ++++++++++++++++++++--
 include/hw/virtio/vhost-backend.h         |   3 +
 include/hw/virtio/virtio-dmabuf.h         | 103 +++++++++++++
 include/qemu/uuid.h                       |   2 +
 subprojects/libvhost-user/libvhost-user.c | 120 ++++++++++++++++
 subprojects/libvhost-user/libvhost-user.h |  55 ++++++-
 tests/unit/meson.build                    |   1 +
 tests/unit/test-uuid.c                    |  27 ++++
 tests/unit/test-virtio-dmabuf.c           | 137 ++++++++++++++++++
 util/uuid.c                               |  15 ++
 14 files changed, 819 insertions(+), 13 deletions(-)
 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

-- 
2.41.0

[PATCH v7 1/4] uuid: add a hash function

[Albert Esteve]

Add hash function to uuid module using the
djb2 hash algorithm.

Add a couple simple unit tests for the hash
function, checking collisions for similar UUIDs.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Albert Esteve <aesteve@redhat.com>
---
 include/qemu/uuid.h    |  2 ++
 tests/unit/test-uuid.c | 27 +++++++++++++++++++++++++++
 util/uuid.c            | 15 +++++++++++++++
 3 files changed, 44 insertions(+)

diff --git a/include/qemu/uuid.h b/include/qemu/uuid.h
index dc40ee1fc9..e24a1099e4 100644
--- a/include/qemu/uuid.h
+++ b/include/qemu/uuid.h
@@ -96,4 +96,6 @@ int qemu_uuid_parse(const char *str, QemuUUID *uuid);
 
 QemuUUID qemu_uuid_bswap(QemuUUID uuid);
 
+uint32_t qemu_uuid_hash(const void *uuid);
+
 #endif
diff --git a/tests/unit/test-uuid.c b/tests/unit/test-uuid.c
index c111de5fc1..aedc125ae9 100644
--- a/tests/unit/test-uuid.c
+++ b/tests/unit/test-uuid.c
@@ -171,6 +171,32 @@ static void test_uuid_unparse_strdup(void)
     }
 }
 
+static void test_uuid_hash(void)
+{
+    QemuUUID uuid;
+    int i;
+
+    for (i = 0; i < 100; i++) {
+        qemu_uuid_generate(&uuid);
+        /* Obtain the UUID hash */
+        uint32_t hash_a = qemu_uuid_hash(&uuid);
+        int data_idx = g_random_int_range(0, 15);
+        /* Change a single random byte of the UUID */
+        if (uuid.data[data_idx] < 0xFF) {
+            uuid.data[data_idx]++;
+        } else {
+            uuid.data[data_idx]--;
+        }
+        /* Obtain the UUID hash again */
+        uint32_t hash_b = qemu_uuid_hash(&uuid);
+        /*
+         * Both hashes shall be different (avoid collision)
+         * for any change in the UUID fields
+         */
+        g_assert_cmpint(hash_a, !=, hash_b);
+    }
+}
+
 int main(int argc, char **argv)
 {
     g_test_init(&argc, &argv, NULL);
@@ -179,6 +205,7 @@ int main(int argc, char **argv)
     g_test_add_func("/uuid/parse", test_uuid_parse);
     g_test_add_func("/uuid/unparse", test_uuid_unparse);
     g_test_add_func("/uuid/unparse_strdup", test_uuid_unparse_strdup);
+    g_test_add_func("/uuid/hash", test_uuid_hash);
 
     return g_test_run();
 }
diff --git a/util/uuid.c b/util/uuid.c
index b1108dde78..b366961bc6 100644
--- a/util/uuid.c
+++ b/util/uuid.c
@@ -116,3 +116,18 @@ QemuUUID qemu_uuid_bswap(QemuUUID uuid)
     bswap16s(&uuid.fields.time_high_and_version);
     return uuid;
 }
+
+/* djb2 hash algorithm */
+uint32_t qemu_uuid_hash(const void *uuid)
+{
+    QemuUUID *qid = (QemuUUID *) uuid;
+    uint32_t h = 5381;
+    int i;
+
+    for (i = 0; i < ARRAY_SIZE(qid->data); i++) {
+        h = (h << 5) + h + qid->data[i];
+    }
+
+    return h;
+}
+
-- 
2.41.0

[PATCH v7 2/4] virtio-dmabuf: introduce virtio-dmabuf

[Albert Esteve]

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

[PATCH v7 3/4] vhost-user: add shared_object msg

[Albert Esteve]

Add three new vhost-user protocol
`VHOST_USER_BACKEND_SHARED_OBJECT_* messages`.
These new messages are sent from vhost-user
back-ends to interact with the virtio-dmabuf
table in order to add or remove themselves as
virtio exporters, or lookup for virtio dma-buf
shared objects.

The action taken in the front-end depends
on the type stored in the virtio shared
object hash table.

When the table holds a pointer to a vhost
backend for a given UUID, the front-end sends
a VHOST_USER_GET_SHARED_OBJECT to the
backend holding the shared object.

The messages can only be sent after successfully
negotiating a new VHOST_USER_PROTOCOL_F_SHARED_OBJECT
vhost-user protocol feature bit.

Finally, refactor code to send response message so
that all common parts both for the common REPLY_ACK
case, and other data responses, can call it and
avoid code repetition.

Signed-off-by: Albert Esteve <aesteve@redhat.com>
---
 docs/interop/vhost-user.rst       |  57 ++++++++++
 hw/virtio/vhost-user.c            | 168 +++++++++++++++++++++++++++---
 include/hw/virtio/vhost-backend.h |   3 +
 3 files changed, 216 insertions(+), 12 deletions(-)

diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst
index 5a070adbc1..415bb47a19 100644
--- a/docs/interop/vhost-user.rst
+++ b/docs/interop/vhost-user.rst
@@ -1440,6 +1440,18 @@ Front-end message types
   query the back-end for its device status as defined in the Virtio
   specification.
 
+``VHOST_USER_GET_SHARED_OBJECT``
+  :id: 41
+  :equivalent ioctl: N/A
+  :request payload: ``struct VhostUserShared``
+  :reply payload: dmabuf fd
+
+  When the ``VHOST_USER_PROTOCOL_F_SHARED_OBJECT`` protocol
+  feature has been successfully negotiated, and the UUID is found
+  in the exporters cache, this message is submitted by the front-end
+  to retrieve a given dma-buf fd from a given back-end, determined by
+  the requested UUID. Back-end will reply passing the fd when the operation
+  is successful, or no fd otherwise.
 
 Back-end message types
 ----------------------
@@ -1528,6 +1540,51 @@ is sent by the front-end.
 
   The state.num field is currently reserved and must be set to 0.
 
+``VHOST_USER_BACKEND_SHARED_OBJECT_ADD``
+  :id: 6
+  :equivalent ioctl: N/A
+  :request payload: ``struct VhostUserShared``
+  :reply payload: N/A
+
+  When the ``VHOST_USER_PROTOCOL_F_SHARED_OBJECT`` protocol
+  feature has been successfully negotiated, this message can be submitted
+  by the backends to add themselves as exporters to the virtio shared lookup
+  table. The back-end device gets associated with a UUID in the shared table.
+  The back-end is responsible of keeping its own table with exported dma-buf fds.
+  When another back-end tries to import the resource associated with the UUID,
+  it will send a message to the front-end, which will act as a proxy to the
+  exporter back-end. If ``VHOST_USER_PROTOCOL_F_REPLY_ACK`` is negotiated, and
+  the back-end sets the ``VHOST_USER_NEED_REPLY`` flag, the front-end must
+  respond with zero when operation is successfully completed, or non-zero
+  otherwise.
+
+``VHOST_USER_BACKEND_SHARED_OBJECT_REMOVE``
+  :id: 7
+  :equivalent ioctl: N/A
+  :request payload: ``struct VhostUserShared``
+  :reply payload: N/A
+
+  When the ``VHOST_USER_PROTOCOL_F_SHARED_OBJECT`` protocol
+  feature has been successfully negotiated, this message can be submitted
+  by the backend to remove themselves from to the virtio-dmabuf shared
+  table API. The shared table will remove the back-end device associated with
+  the UUID. If ``VHOST_USER_PROTOCOL_F_REPLY_ACK`` is negotiated, and the
+  back-end sets the ``VHOST_USER_NEED_REPLY`` flag, the front-end must respond
+  with zero when operation is successfully completed, or non-zero otherwise.
+
+``VHOST_USER_BACKEND_SHARED_OBJECT_LOOKUP``
+  :id: 8
+  :equivalent ioctl: N/A
+  :request payload: ``struct VhostUserShared``
+  :reply payload: dmabuf fd and ``u64``
+
+  When the ``VHOST_USER_PROTOCOL_F_SHARED_OBJECT`` protocol
+  feature has been successfully negotiated, this message can be submitted
+  by the backends to retrieve a given dma-buf fd from the virtio-dmabuf
+  shared table given a UUID. Frontend will reply passing the fd and a zero
+  when the operation is successful, or non-zero otherwise. Note that if the
+  operation fails, no fd is sent to the backend.
+
 .. _reply_ack:
 
 VHOST_USER_PROTOCOL_F_REPLY_ACK
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 8dcf049d42..08ab256613 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -10,6 +10,7 @@
 
 #include "qemu/osdep.h"
 #include "qapi/error.h"
+#include "hw/virtio/virtio-dmabuf.h"
 #include "hw/virtio/vhost.h"
 #include "hw/virtio/virtio-crypto.h"
 #include "hw/virtio/vhost-user.h"
@@ -21,6 +22,7 @@
 #include "sysemu/kvm.h"
 #include "qemu/error-report.h"
 #include "qemu/main-loop.h"
+#include "qemu/uuid.h"
 #include "qemu/sockets.h"
 #include "sysemu/runstate.h"
 #include "sysemu/cryptodev.h"
@@ -74,6 +76,7 @@ enum VhostUserProtocolFeature {
     /* Feature 14 reserved for VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS. */
     VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS = 15,
     VHOST_USER_PROTOCOL_F_STATUS = 16,
+    VHOST_USER_PROTOCOL_F_SHARED_OBJECT = 17,
     VHOST_USER_PROTOCOL_F_MAX
 };
 
@@ -121,6 +124,7 @@ typedef enum VhostUserRequest {
     VHOST_USER_REM_MEM_REG = 38,
     VHOST_USER_SET_STATUS = 39,
     VHOST_USER_GET_STATUS = 40,
+    VHOST_USER_GET_SHARED_OBJECT = 41,
     VHOST_USER_MAX
 } VhostUserRequest;
 
@@ -129,6 +133,9 @@ typedef enum VhostUserBackendRequest {
     VHOST_USER_BACKEND_IOTLB_MSG = 1,
     VHOST_USER_BACKEND_CONFIG_CHANGE_MSG = 2,
     VHOST_USER_BACKEND_VRING_HOST_NOTIFIER_MSG = 3,
+    VHOST_USER_BACKEND_SHARED_OBJECT_ADD = 6,
+    VHOST_USER_BACKEND_SHARED_OBJECT_REMOVE = 7,
+    VHOST_USER_BACKEND_SHARED_OBJECT_LOOKUP = 8,
     VHOST_USER_BACKEND_MAX
 }  VhostUserBackendRequest;
 
@@ -202,6 +209,10 @@ typedef struct VhostUserInflight {
     uint16_t queue_size;
 } VhostUserInflight;
 
+typedef struct VhostUserShared {
+    unsigned char uuid[16];
+} VhostUserShared;
+
 typedef struct {
     VhostUserRequest request;
 
@@ -226,6 +237,7 @@ typedef union {
         VhostUserCryptoSession session;
         VhostUserVringArea area;
         VhostUserInflight inflight;
+        VhostUserShared object;
 } VhostUserPayload;
 
 typedef struct VhostUserMsg {
@@ -1601,6 +1613,139 @@ static int vhost_user_backend_handle_vring_host_notifier(struct vhost_dev *dev,
     return 0;
 }
 
+static int
+vhost_user_backend_handle_shared_object_add(struct vhost_dev *dev,
+                                            VhostUserShared *object)
+{
+    QemuUUID uuid;
+
+    memcpy(uuid.data, object->uuid, sizeof(object->uuid));
+    return virtio_add_vhost_device(&uuid, dev);
+}
+
+static int
+vhost_user_backend_handle_shared_object_remove(VhostUserShared *object)
+{
+    QemuUUID uuid;
+
+    memcpy(uuid.data, object->uuid, sizeof(object->uuid));
+    return virtio_remove_resource(&uuid);
+}
+
+static bool vhost_user_send_resp(QIOChannel *ioc, VhostUserHeader *hdr,
+                                 VhostUserPayload *payload, Error **errp)
+{
+    struct iovec iov[] = {
+        { .iov_base = hdr,      .iov_len = VHOST_USER_HDR_SIZE },
+        { .iov_base = payload,  .iov_len = hdr->size },
+    };
+
+    hdr->flags &= ~VHOST_USER_NEED_REPLY_MASK;
+    hdr->flags |= VHOST_USER_REPLY_MASK;
+
+    return !qio_channel_writev_all(ioc, iov, ARRAY_SIZE(iov), errp);
+}
+
+static bool
+vhost_user_backend_send_dmabuf_fd(QIOChannel *ioc, VhostUserHeader *hdr,
+                                  VhostUserPayload *payload, Error **errp)
+{
+    hdr->size = sizeof(payload->u64);
+    return vhost_user_send_resp(ioc, hdr, payload, errp);
+}
+
+int vhost_user_get_shared_object(struct vhost_dev *dev, unsigned char *uuid,
+                                 int *dmabuf_fd)
+{
+    struct vhost_user *u = dev->opaque;
+    CharBackend *chr = u->user->chr;
+    int ret;
+    VhostUserMsg msg = {
+        .hdr.request = VHOST_USER_GET_SHARED_OBJECT,
+        .hdr.flags = VHOST_USER_VERSION,
+    };
+    memcpy(msg.payload.object.uuid, uuid, sizeof(msg.payload.object.uuid));
+
+    ret = vhost_user_write(dev, &msg, NULL, 0);
+    if (ret < 0) {
+        return ret;
+    }
+
+    ret = vhost_user_read(dev, &msg);
+    if (ret < 0) {
+        return ret;
+    }
+
+    if (msg.hdr.request != VHOST_USER_GET_SHARED_OBJECT) {
+        error_report("Received unexpected msg type. "
+                     "Expected %d received %d",
+                     VHOST_USER_GET_SHARED_OBJECT, msg.hdr.request);
+        return -EPROTO;
+    }
+
+    *dmabuf_fd = qemu_chr_fe_get_msgfd(chr);
+    if (*dmabuf_fd < 0) {
+        error_report("Failed to get dmabuf fd");
+        return -EIO;
+    }
+
+    return 0;
+}
+
+static int
+vhost_user_backend_handle_shared_object_lookup(struct vhost_user *u,
+                                               QIOChannel *ioc,
+                                               VhostUserHeader *hdr,
+                                               VhostUserPayload *payload)
+{
+    QemuUUID uuid;
+    CharBackend *chr = u->user->chr;
+    Error *local_err = NULL;
+    int dmabuf_fd = -1;
+    int fd_num = 0;
+
+    memcpy(uuid.data, payload->object.uuid, sizeof(payload->object.uuid));
+
+    payload->u64 = 0;
+    switch (virtio_object_type(&uuid)) {
+    case TYPE_DMABUF:
+        dmabuf_fd = virtio_lookup_dmabuf(&uuid);
+        break;
+    case TYPE_VHOST_DEV:
+    {
+        struct vhost_dev *dev = virtio_lookup_vhost_device(&uuid);
+        if (dev == NULL) {
+            payload->u64 = -EINVAL;
+            break;
+        }
+        int ret = vhost_user_get_shared_object(dev, uuid.data, &dmabuf_fd);
+        if (ret < 0) {
+            payload->u64 = ret;
+        }
+        break;
+    }
+    case TYPE_INVALID:
+        payload->u64 = -EINVAL;
+        break;
+    }
+
+    if (dmabuf_fd != -1) {
+        fd_num++;
+    }
+
+    if (qemu_chr_fe_set_msgfds(chr, &dmabuf_fd, fd_num) < 0) {
+        error_report("Failed to set msg fds.");
+        payload->u64 = -EINVAL;
+    }
+
+    if (!vhost_user_backend_send_dmabuf_fd(ioc, hdr, payload, &local_err)) {
+        error_report_err(local_err);
+        return -EINVAL;
+    }
+
+    return 0;
+}
+
 static void close_backend_channel(struct vhost_user *u)
 {
     g_source_destroy(u->backend_src);
@@ -1658,6 +1803,16 @@ static gboolean backend_read(QIOChannel *ioc, GIOCondition condition,
         ret = vhost_user_backend_handle_vring_host_notifier(dev, &payload.area,
                                                           fd ? fd[0] : -1);
         break;
+    case VHOST_USER_BACKEND_SHARED_OBJECT_ADD:
+        ret = vhost_user_backend_handle_shared_object_add(dev, &payload.object);
+        break;
+    case VHOST_USER_BACKEND_SHARED_OBJECT_REMOVE:
+        ret = vhost_user_backend_handle_shared_object_remove(&payload.object);
+        break;
+    case VHOST_USER_BACKEND_SHARED_OBJECT_LOOKUP:
+        ret = vhost_user_backend_handle_shared_object_lookup(dev->opaque, ioc,
+                                                             &hdr, &payload);
+        break;
     default:
         error_report("Received unexpected msg type: %d.", hdr.request);
         ret = -EINVAL;
@@ -1668,21 +1823,10 @@ static gboolean backend_read(QIOChannel *ioc, GIOCondition condition,
      * directly in their request handlers.
      */
     if (hdr.flags & VHOST_USER_NEED_REPLY_MASK) {
-        struct iovec iovec[2];
-
-
-        hdr.flags &= ~VHOST_USER_NEED_REPLY_MASK;
-        hdr.flags |= VHOST_USER_REPLY_MASK;
-
         payload.u64 = !!ret;
         hdr.size = sizeof(payload.u64);
 
-        iovec[0].iov_base = &hdr;
-        iovec[0].iov_len = VHOST_USER_HDR_SIZE;
-        iovec[1].iov_base = &payload;
-        iovec[1].iov_len = hdr.size;
-
-        if (qio_channel_writev_all(ioc, iovec, ARRAY_SIZE(iovec), &local_err)) {
+        if (!vhost_user_send_resp(ioc, &hdr, &payload, &local_err)) {
             error_report_err(local_err);
             goto err;
         }
diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
index 31a251a9f5..1860b541d8 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -196,4 +196,7 @@ int vhost_backend_handle_iotlb_msg(struct vhost_dev *dev,
 
 int vhost_user_gpu_set_socket(struct vhost_dev *dev, int fd);
 
+int vhost_user_get_shared_object(struct vhost_dev *dev, unsigned char *uuid,
+                                        int *dmabuf_fd);
+
 #endif /* VHOST_BACKEND_H */
-- 
2.41.0

[PATCH v7 4/4] libvhost-user: handle shared_object msg

[Albert Esteve]

In the libvhost-user library we need to
handle VHOST_USER_GET_SHARED_OBJECT requests,
and add helper functions to allow sending messages
to interact with the virtio shared objects
hash table.

Signed-off-by: Albert Esteve <aesteve@redhat.com>
---
 subprojects/libvhost-user/libvhost-user.c | 120 ++++++++++++++++++++++
 subprojects/libvhost-user/libvhost-user.h |  55 +++++++++-
 2 files changed, 174 insertions(+), 1 deletion(-)

diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
index 0469a50101..676e57a468 100644
--- a/subprojects/libvhost-user/libvhost-user.c
+++ b/subprojects/libvhost-user/libvhost-user.c
@@ -161,6 +161,7 @@ vu_request_to_string(unsigned int req)
         REQ(VHOST_USER_GET_MAX_MEM_SLOTS),
         REQ(VHOST_USER_ADD_MEM_REG),
         REQ(VHOST_USER_REM_MEM_REG),
+        REQ(VHOST_USER_GET_SHARED_OBJECT),
         REQ(VHOST_USER_MAX),
     };
 #undef REQ
@@ -900,6 +901,24 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
     return false;
 }
 
+static bool
+vu_get_shared_object(VuDev *dev, VhostUserMsg *vmsg)
+{
+    int fd_num = 0;
+    int dmabuf_fd = -1;
+    if (dev->iface->get_shared_object) {
+        dmabuf_fd = dev->iface->get_shared_object(
+            dev, &vmsg->payload.object.uuid[0]);
+    }
+    if (dmabuf_fd != -1) {
+        DPRINT("dmabuf_fd found for requested UUID\n");
+        vmsg->fds[fd_num++] = dmabuf_fd;
+    }
+    vmsg->fd_num = fd_num;
+
+    return true;
+}
+
 static bool
 vu_set_mem_table_exec_postcopy(VuDev *dev, VhostUserMsg *vmsg)
 {
@@ -1403,6 +1422,105 @@ bool vu_set_queue_host_notifier(VuDev *dev, VuVirtq *vq, int fd,
     return vu_process_message_reply(dev, &vmsg);
 }
 
+bool
+vu_lookup_shared_object(VuDev *dev, unsigned char uuid[UUID_LEN],
+                        int *dmabuf_fd)
+{
+    bool result = false;
+    VhostUserMsg msg_reply;
+    VhostUserMsg msg = {
+        .request = VHOST_USER_BACKEND_SHARED_OBJECT_LOOKUP,
+        .size = sizeof(msg.payload.object),
+        .flags = VHOST_USER_VERSION | VHOST_USER_NEED_REPLY_MASK,
+    };
+
+    memcpy(msg.payload.object.uuid, uuid, sizeof(uuid[0]) * UUID_LEN);
+
+    if (!vu_has_protocol_feature(dev, VHOST_USER_PROTOCOL_F_SHARED_OBJECT)) {
+        return false;
+    }
+
+    pthread_mutex_lock(&dev->backend_mutex);
+    if (!vu_message_write(dev, dev->backend_fd, &msg)) {
+        goto out;
+    }
+
+    if (!vu_message_read_default(dev, dev->backend_fd, &msg_reply)) {
+        goto out;
+    }
+
+    if (msg_reply.request != msg.request) {
+        DPRINT("Received unexpected msg type. Expected %d, received %d",
+               msg.request, msg_reply.request);
+        goto out;
+    }
+
+    if (msg_reply.fd_num != 1) {
+        DPRINT("Received unexpected number of fds. Expected 1, received %d",
+               msg_reply.fd_num);
+        goto out;
+    }
+
+    *dmabuf_fd = msg_reply.fds[0];
+    result = *dmabuf_fd > 0 && msg_reply.payload.u64 == 0;
+out:
+    pthread_mutex_unlock(&dev->backend_mutex);
+
+    return result;
+}
+
+static bool
+vu_send_message(VuDev *dev, VhostUserMsg *vmsg)
+{
+    bool result = false;
+    pthread_mutex_lock(&dev->backend_mutex);
+    if (!vu_message_write(dev, dev->backend_fd, vmsg)) {
+        goto out;
+    }
+
+    result = true;
+out:
+    pthread_mutex_unlock(&dev->backend_mutex);
+
+    return result;
+}
+
+bool
+vu_add_shared_object(VuDev *dev, unsigned char uuid[UUID_LEN])
+{
+    VhostUserMsg msg = {
+        .request = VHOST_USER_BACKEND_SHARED_OBJECT_ADD,
+        .size = sizeof(msg.payload.object),
+        .flags = VHOST_USER_VERSION,
+    };
+
+    memcpy(msg.payload.object.uuid, uuid, sizeof(uuid[0]) * UUID_LEN);
+
+    if (!vu_has_protocol_feature(dev, VHOST_USER_PROTOCOL_F_SHARED_OBJECT)) {
+        return false;
+    }
+
+    return vu_send_message(dev, &msg);
+}
+
+bool
+vu_rm_shared_object(VuDev *dev, unsigned char uuid[UUID_LEN])
+{
+    VhostUserMsg msg = {
+        .request = VHOST_USER_BACKEND_SHARED_OBJECT_REMOVE,
+        .size = sizeof(msg.payload.object),
+        .flags = VHOST_USER_VERSION,
+    };
+
+    memcpy(msg.payload.object.uuid, uuid, sizeof(uuid[0]) * UUID_LEN);
+
+    if (!vu_has_protocol_feature(dev, VHOST_USER_PROTOCOL_F_SHARED_OBJECT)) {
+        return false;
+    }
+
+    return vu_send_message(dev, &msg);
+}
+
 static bool
 vu_set_vring_call_exec(VuDev *dev, VhostUserMsg *vmsg)
 {
@@ -1943,6 +2061,8 @@ vu_process_message(VuDev *dev, VhostUserMsg *vmsg)
         return vu_add_mem_reg(dev, vmsg);
     case VHOST_USER_REM_MEM_REG:
         return vu_rem_mem_reg(dev, vmsg);
+    case VHOST_USER_GET_SHARED_OBJECT:
+        return vu_get_shared_object(dev, vmsg);
     default:
         vmsg_close_fds(vmsg);
         vu_panic(dev, "Unhandled request: %d", vmsg->request);
diff --git a/subprojects/libvhost-user/libvhost-user.h b/subprojects/libvhost-user/libvhost-user.h
index 708370c5f5..b36a42a7ca 100644
--- a/subprojects/libvhost-user/libvhost-user.h
+++ b/subprojects/libvhost-user/libvhost-user.h
@@ -64,7 +64,8 @@ enum VhostUserProtocolFeature {
     VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
     VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS = 14,
     VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS = 15,
-
+    /* Feature 16 is reserved for VHOST_USER_PROTOCOL_F_STATUS. */
+    VHOST_USER_PROTOCOL_F_SHARED_OBJECT = 17,
     VHOST_USER_PROTOCOL_F_MAX
 };
 
@@ -109,6 +110,7 @@ typedef enum VhostUserRequest {
     VHOST_USER_GET_MAX_MEM_SLOTS = 36,
     VHOST_USER_ADD_MEM_REG = 37,
     VHOST_USER_REM_MEM_REG = 38,
+    VHOST_USER_GET_SHARED_OBJECT = 41,
     VHOST_USER_MAX
 } VhostUserRequest;
 
@@ -119,6 +121,9 @@ typedef enum VhostUserBackendRequest {
     VHOST_USER_BACKEND_VRING_HOST_NOTIFIER_MSG = 3,
     VHOST_USER_BACKEND_VRING_CALL = 4,
     VHOST_USER_BACKEND_VRING_ERR = 5,
+    VHOST_USER_BACKEND_SHARED_OBJECT_ADD = 6,
+    VHOST_USER_BACKEND_SHARED_OBJECT_REMOVE = 7,
+    VHOST_USER_BACKEND_SHARED_OBJECT_LOOKUP = 8,
     VHOST_USER_BACKEND_MAX
 }  VhostUserBackendRequest;
 
@@ -172,6 +177,12 @@ typedef struct VhostUserInflight {
     uint16_t queue_size;
 } VhostUserInflight;
 
+#define UUID_LEN 16
+
+typedef struct VhostUserShared {
+    unsigned char uuid[UUID_LEN];
+} VhostUserShared;
+
 #if defined(_WIN32) && (defined(__x86_64__) || defined(__i386__))
 # define VU_PACKED __attribute__((gcc_struct, packed))
 #else
@@ -199,6 +210,7 @@ typedef struct VhostUserMsg {
         VhostUserConfig config;
         VhostUserVringArea area;
         VhostUserInflight inflight;
+        VhostUserShared object;
     } payload;
 
     int fds[VHOST_MEMORY_BASELINE_NREGIONS];
@@ -232,6 +244,7 @@ typedef int (*vu_get_config_cb) (VuDev *dev, uint8_t *config, uint32_t len);
 typedef int (*vu_set_config_cb) (VuDev *dev, const uint8_t *data,
                                  uint32_t offset, uint32_t size,
                                  uint32_t flags);
+typedef int (*vu_get_shared_object_cb) (VuDev *dev, const unsigned char *uuid);
 
 typedef struct VuDevIface {
     /* called by VHOST_USER_GET_FEATURES to get the features bitmask */
@@ -258,6 +271,8 @@ typedef struct VuDevIface {
     vu_get_config_cb get_config;
     /* set the config space of the device */
     vu_set_config_cb set_config;
+    /* get virtio shared object from the underlying vhost implementation. */
+    vu_get_shared_object_cb get_shared_object;
 } VuDevIface;
 
 typedef void (*vu_queue_handler_cb) (VuDev *dev, int qidx);
@@ -541,6 +556,44 @@ void vu_set_queue_handler(VuDev *dev, VuVirtq *vq,
 bool vu_set_queue_host_notifier(VuDev *dev, VuVirtq *vq, int fd,
                                 int size, int offset);
 
+/**
+ * vu_lookup_shared_object:
+ * @dev: a VuDev context
+ * @uuid: UUID of the shared object
+ * @dmabuf_fd: output dma-buf file descriptor
+ *
+ * Lookup for a virtio shared object (i.e., dma-buf fd) associated with the
+ * received UUID. Result, if found, is stored in the dmabuf_fd argument.
+ *
+ * Returns: whether the virtio object was found.
+ */
+bool vu_lookup_shared_object(VuDev *dev, unsigned char uuid[UUID_LEN],
+                             int *dmabuf_fd);
+
+/**
+ * vu_add_shared_object:
+ * @dev: a VuDev context
+ * @uuid: UUID of the shared object
+ *
+ * Registers this back-end as the exporter for the object associated with
+ * the received UUID.
+ *
+ * Returns: TRUE on success, FALSE on failure.
+ */
+bool vu_add_shared_object(VuDev *dev, unsigned char uuid[UUID_LEN]);
+
+/**
+ * vu_rm_shared_object:
+ * @dev: a VuDev context
+ * @uuid: UUID of the shared object
+ *
+ * Removes a shared object entry (i.e., back-end entry) associated with the
+ * received UUID key from the hash table.
+ *
+ * Returns: TRUE on success, FALSE on failure.
+ */
+bool vu_rm_shared_object(VuDev *dev, unsigned char uuid[UUID_LEN]);
+
 /**
  * vu_queue_set_notification:
  * @dev: a VuDev context
-- 
2.41.0

Re: [PATCH v7 2/4] virtio-dmabuf: introduce virtio-dmabuf

[Philippe Mathieu-Daudé]

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>

Re: [PATCH v7 2/4] virtio-dmabuf: introduce virtio-dmabuf

[Albert Esteve]

[-- Attachment #1: Type: text/plain, Size: 2913 bytes --]

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?

[-- Attachment #2: Type: text/html, Size: 4197 bytes --]