[Qemu-devel] [PATCH v4 08/29] Add vhost-user-backend

[Marc-André Lureau]

Create a vhost-user-backend object that holds a connection to a
vhost-user backend and can be referenced from virtio devices that
support it. See later patches for input & gpu usage.

A chardev can be specified to communicate with the vhost-user backend,
ex: -chardev socket,id=char0,path=/tmp/foo.sock -object
vhost-user-backend,id=vuid,chardev=char0.

Signed-off-by: Marc-André Lureau <address@hidden>
---
 include/sysemu/vhost-user-backend.h |  60 +++++++
 backends/vhost-user.c               | 244 ++++++++++++++++++++++++++++
 vl.c                                |   3 +-
 MAINTAINERS                         |   2 +
 backends/Makefile.objs              |   3 +-
 qemu-options.hx                     |  20 +++
 6 files changed, 330 insertions(+), 2 deletions(-)
 create mode 100644 include/sysemu/vhost-user-backend.h
 create mode 100644 backends/vhost-user.c

diff --git a/include/sysemu/vhost-user-backend.h 
b/include/sysemu/vhost-user-backend.h
new file mode 100644
index 0000000000..60f811cae7
--- /dev/null
+++ b/include/sysemu/vhost-user-backend.h
@@ -0,0 +1,60 @@
+/*
+ * QEMU vhost-user backend
+ *
+ * Copyright (C) 2018 Red Hat Inc
+ *
+ * Authors:
+ *  Marc-André Lureau <address@hidden>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+#ifndef QEMU_VHOST_USER_BACKEND_H
+#define QEMU_VHOST_USER_BACKEND_H
+
+#include "qom/object.h"
+#include "exec/memory.h"
+#include "qemu/option.h"
+#include "qemu/bitmap.h"
+#include "hw/virtio/vhost.h"
+#include "hw/virtio/vhost-user.h"
+#include "chardev/char-fe.h"
+#include "io/channel.h"
+
+#define TYPE_VHOST_USER_BACKEND "vhost-user-backend"
+#define VHOST_USER_BACKEND(obj) \
+    OBJECT_CHECK(VhostUserBackend, (obj), TYPE_VHOST_USER_BACKEND)
+#define VHOST_USER_BACKEND_GET_CLASS(obj) \
+    OBJECT_GET_CLASS(VhostUserBackendClass, (obj), TYPE_VHOST_USER_BACKEND)
+#define VHOST_USER_BACKEND_CLASS(klass) \
+    OBJECT_CLASS_CHECK(VhostUserBackendClass, (klass), TYPE_VHOST_USER_BACKEND)
+
+typedef struct VhostUserBackend VhostUserBackend;
+typedef struct VhostUserBackendClass VhostUserBackendClass;
+
+struct VhostUserBackendClass {
+    ObjectClass parent_class;
+};
+
+struct VhostUserBackend {
+    /* private */
+    Object parent;
+
+    char *cmd;
+    char *chr_name;
+
+    CharBackend chr;
+    VhostUserState vhost_user;
+    struct vhost_dev dev;
+    QIOChannel *child;
+    VirtIODevice *vdev;
+    bool started;
+    bool completed;
+};
+
+int vhost_user_backend_dev_init(VhostUserBackend *b, VirtIODevice *vdev,
+                                unsigned nvqs, Error **errp);
+void vhost_user_backend_start(VhostUserBackend *b);
+void vhost_user_backend_stop(VhostUserBackend *b);
+
+#endif
diff --git a/backends/vhost-user.c b/backends/vhost-user.c
new file mode 100644
index 0000000000..bf39c0751d
--- /dev/null
+++ b/backends/vhost-user.c
@@ -0,0 +1,244 @@
+/*
+ * QEMU vhost-user backend
+ *
+ * Copyright (C) 2018 Red Hat Inc
+ *
+ * Authors:
+ *  Marc-André Lureau <address@hidden>
+ *
+ * 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/qdev.h"
+#include "qapi/error.h"
+#include "qapi/qmp/qerror.h"
+#include "qemu/error-report.h"
+#include "qom/object_interfaces.h"
+#include "sysemu/vhost-user-backend.h"
+#include "sysemu/kvm.h"
+#include "io/channel-command.h"
+#include "hw/virtio/virtio-bus.h"
+
+static bool
+ioeventfd_enabled(void)
+{
+    return kvm_enabled() && kvm_eventfds_enabled();
+}
+
+int
+vhost_user_backend_dev_init(VhostUserBackend *b, VirtIODevice *vdev,
+                            unsigned nvqs, Error **errp)
+{
+    int ret;
+
+    assert(!b->vdev && vdev);
+
+    if (!ioeventfd_enabled()) {
+        error_setg(errp, "vhost initialization failed: requires kvm");
+        return -1;
+    }
+
+    if (!vhost_user_init(&b->vhost_user, &b->chr, errp)) {
+        return -1;
+    }
+
+    b->vdev = vdev;
+    b->dev.nvqs = nvqs;
+    b->dev.vqs = g_new(struct vhost_virtqueue, nvqs);
+
+    ret = vhost_dev_init(&b->dev, &b->vhost_user, VHOST_BACKEND_TYPE_USER, 0);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "vhost initialization failed");
+        return -1;
+    }
+
+    return 0;
+}
+
+void
+vhost_user_backend_start(VhostUserBackend *b)
+{
+    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(b->vdev)));
+    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+    int ret, i ;
+
+    if (b->started) {
+        return;
+    }
+
+    if (!k->set_guest_notifiers) {
+        error_report("binding does not support guest notifiers");
+        return;
+    }
+
+    ret = vhost_dev_enable_notifiers(&b->dev, b->vdev);
+    if (ret < 0) {
+        return;
+    }
+
+    ret = k->set_guest_notifiers(qbus->parent, b->dev.nvqs, true);
+    if (ret < 0) {
+        error_report("Error binding guest notifier");
+        goto err_host_notifiers;
+    }
+
+    b->dev.acked_features = b->vdev->guest_features;
+    ret = vhost_dev_start(&b->dev, b->vdev);
+    if (ret < 0) {
+        error_report("Error start vhost dev");
+        goto err_guest_notifiers;
+    }
+
+    /* guest_notifier_mask/pending not used yet, so just unmask
+     * everything here.  virtio-pci will do the right thing by
+     * enabling/disabling irqfd.
+     */
+    for (i = 0; i < b->dev.nvqs; i++) {
+        vhost_virtqueue_mask(&b->dev, b->vdev,
+                             b->dev.vq_index + i, false);
+    }
+
+    b->started = true;
+    return;
+
+err_guest_notifiers:
+    k->set_guest_notifiers(qbus->parent, b->dev.nvqs, false);
+err_host_notifiers:
+    vhost_dev_disable_notifiers(&b->dev, b->vdev);
+}
+
+void
+vhost_user_backend_stop(VhostUserBackend *b)
+{
+    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(b->vdev)));
+    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+    int ret = 0;
+
+    if (!b->started) {
+        return;
+    }
+
+    vhost_dev_stop(&b->dev, b->vdev);
+
+    if (k->set_guest_notifiers) {
+        ret = k->set_guest_notifiers(qbus->parent,
+                                     b->dev.nvqs, false);
+        if (ret < 0) {
+            error_report("vhost guest notifier cleanup failed: %d", ret);
+        }
+    }
+    assert(ret >= 0);
+
+    vhost_dev_disable_notifiers(&b->dev, b->vdev);
+    b->started = false;
+}
+
+static void
+vhost_user_backend_complete(UserCreatable *uc, Error **errp)
+{
+    VhostUserBackend *b = VHOST_USER_BACKEND(uc);
+    Chardev *chr;
+
+    if (!b->chr_name) {
+        error_setg(errp, "You must specificy 'chardev'.");
+        return;
+    }
+
+    chr = qemu_chr_find(b->chr_name);
+    if (chr == NULL) {
+        error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
+                  "Chardev '%s' not found", b->chr_name);
+        return;
+    }
+
+    if (!qemu_chr_fe_init(&b->chr, chr, errp)) {
+        return;
+    }
+
+    b->completed = true;
+    /* could vhost_dev_init() happen here, so early vhost-user message
+     * can be exchanged */
+}
+
+static void set_chardev(Object *obj, const char *value, Error **errp)
+{
+    VhostUserBackend *b = VHOST_USER_BACKEND(obj);
+
+    if (b->completed) {
+        error_setg(errp, QERR_PERMISSION_DENIED);
+    } else {
+        g_free(b->chr_name);
+        b->chr_name = g_strdup(value);
+    }
+}
+
+static char *get_chardev(Object *obj, Error **errp)
+{
+    VhostUserBackend *b = VHOST_USER_BACKEND(obj);
+    Chardev *chr = qemu_chr_fe_get_driver(&b->chr);
+
+    if (chr && chr->label) {
+        return g_strdup(chr->label);
+    }
+
+    return NULL;
+}
+
+static void vhost_user_backend_init(Object *obj)
+{
+    object_property_add_str(obj, "chardev", get_chardev, set_chardev, NULL);
+}
+
+static void vhost_user_backend_finalize(Object *obj)
+{
+    VhostUserBackend *b = VHOST_USER_BACKEND(obj);
+
+    g_free(b->dev.vqs);
+    g_free(b->chr_name);
+
+    vhost_user_cleanup(&b->vhost_user);
+    qemu_chr_fe_deinit(&b->chr, true);
+
+    if (b->child) {
+        object_unref(OBJECT(b->child));
+    }
+}
+
+static bool
+vhost_user_backend_can_be_deleted(UserCreatable *uc)
+{
+    return true;
+}
+
+static void
+vhost_user_backend_class_init(ObjectClass *oc, void *data)
+{
+    UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
+
+    ucc->complete = vhost_user_backend_complete;
+    ucc->can_be_deleted = vhost_user_backend_can_be_deleted;
+}
+
+static const TypeInfo vhost_user_backend_info = {
+    .name = TYPE_VHOST_USER_BACKEND,
+    .parent = TYPE_OBJECT,
+    .instance_size = sizeof(VhostUserBackend),
+    .instance_init = vhost_user_backend_init,
+    .instance_finalize = vhost_user_backend_finalize,
+    .class_size = sizeof(VhostUserBackendClass),
+    .class_init = vhost_user_backend_class_init,
+    .interfaces = (InterfaceInfo[]) {
+        { TYPE_USER_CREATABLE },
+        { }
+    }
+};
+
+static void register_types(void)
+{
+    type_register_static(&vhost_user_backend_info);
+}
+
+type_init(register_types);
diff --git a/vl.c b/vl.c
index 16b913f9d5..5272b4939f 100644
--- a/vl.c
+++ b/vl.c
@@ -2737,7 +2737,8 @@ static bool object_create_initial(const char *type)
     }
 
 #if defined(CONFIG_VHOST_USER) && defined(CONFIG_LINUX)
-    if (g_str_equal(type, "cryptodev-vhost-user")) {
+    if (g_str_equal(type, "cryptodev-vhost-user") ||
+        g_str_equal(type, "vhost-user-backend")) {
         return false;
     }
 #endif
diff --git a/MAINTAINERS b/MAINTAINERS
index 20eef3cb61..dd8d07651f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1189,6 +1189,8 @@ M: Michael S. Tsirkin <address@hidden>
 S: Supported
 F: hw/*/*vhost*
 F: docs/interop/vhost-user.txt
+F: backends/vhost-user.c
+F: include/sysemu/vhost-user-backend.h
 
 virtio
 M: Michael S. Tsirkin <address@hidden>
diff --git a/backends/Makefile.objs b/backends/Makefile.objs
index ad7c0325ed..1ffcf76bb1 100644
--- a/backends/Makefile.objs
+++ b/backends/Makefile.objs
@@ -12,7 +12,8 @@ common-obj-y += cryptodev-builtin.o
 ifeq ($(CONFIG_VIRTIO),y)
 common-obj-y += cryptodev-vhost.o
 common-obj-$(call land,$(CONFIG_VHOST_USER),$(CONFIG_LINUX)) += \
-    cryptodev-vhost-user.o
+    cryptodev-vhost-user.o \
+    vhost-user.o
 endif
 
 common-obj-$(CONFIG_LINUX) += hostmem-memfd.o
diff --git a/qemu-options.hx b/qemu-options.hx
index 654e69cc3b..413b97d5e9 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4292,6 +4292,26 @@ secondary:
 If you want to know the detail of above command line, you can read
 the colo-compare git log.
 
address@hidden -object vhost-user-backend,address@hidden,address@hidden
+
+Create a vhost-user-backend object that holds a connection to a
+vhost-user backend and can be referenced from virtio/vhost-user
+devices that support it.
+
+The @var{id} parameter is a unique ID that will be used to reference
+this vhost-user backend from the @option{vhost-user} device. The
address@hidden parameter is the unique ID of a character device backend
+that provides the connection to the vhost-user slave process. (Since 3.0)
+
address@hidden
+
+ # qemu-system-x86_64 \
+   [...] \
+   -object vhost-user-backend,id=vuid,chardev=char0 \
+   -device vhost-user-input-pci,vhost-user=vuid
+   [...]
address@hidden example
+
 @item -object cryptodev-backend-builtin,address@hidden,address@hidden
 
 Creates a cryptodev backend which executes crypto opreation from
-- 
2.18.0.129.ge3331758f1