virtio: add vhost-user-fs base device

The virtio-fs virtio device provides shared file system access using
the FUSE protocol carried over virtio.
The actual file server is implemented in an external vhost-user-fs device
backend process.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20190930105135.27244-3-dgilbert@redhat.com>
Acked-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

configure

@@ -381,6 +381,7 @@ vhost_crypto=""
 vhost_scsi=""
 vhost_vsock=""
 vhost_user=""
+vhost_user_fs=""
 kvm="no"
 hax="no"
 hvf="no"
@@ -1293,6 +1294,10 @@ for opt do
   ;;
   --enable-vhost-vsock) vhost_vsock="yes"
   ;;
+  --disable-vhost-user-fs) vhost_user_fs="no"
+  ;;
+  --enable-vhost-user-fs) vhost_user_fs="yes"
+  ;;
   --disable-opengl) opengl="no"
   ;;
   --enable-opengl) opengl="yes"
@@ -2236,6 +2241,10 @@ test "$vhost_crypto" = "" && vhost_crypto=$vhost_user
 if test "$vhost_crypto" = "yes" && test "$vhost_user" = "no"; then
   error_exit "--enable-vhost-crypto requires --enable-vhost-user"
 fi
+test "$vhost_user_fs" = "" && vhost_user_fs=$vhost_user
+if test "$vhost_user_fs" = "yes" && test "$vhost_user" = "no"; then
+  error_exit "--enable-vhost-user-fs requires --enable-vhost-user"
+fi
 
 # OR the vhost-kernel and vhost-user values for simplicity
 if test "$vhost_net" = ""; then
@@ -6377,6 +6386,7 @@ echo "vhost-crypto support $vhost_crypto"
 echo "vhost-scsi support $vhost_scsi"
 echo "vhost-vsock support $vhost_vsock"
 echo "vhost-user support $vhost_user"
+echo "vhost-user-fs support $vhost_user_fs"
 echo "Trace backends    $trace_backends"
 if have_backend "simple"; then
 echo "Trace output file $trace_file-<pid>"
@@ -6873,6 +6883,9 @@ fi
 if test "$vhost_user" = "yes" ; then
   echo "CONFIG_VHOST_USER=y" >> $config_host_mak
 fi
+if test "$vhost_user_fs" = "yes" ; then
+  echo "CONFIG_VHOST_USER_FS=y" >> $config_host_mak
+fi
 if test "$blobs" = "yes" ; then
   echo "INSTALL_BLOBS=yes" >> $config_host_mak
 fi

hw/virtio/Makefile.objs

@@ -11,6 +11,7 @@ common-obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o
 common-obj-$(CONFIG_VIRTIO_MMIO) += virtio-mmio.o
 obj-$(CONFIG_VIRTIO_BALLOON) += virtio-balloon.o
 obj-$(CONFIG_VIRTIO_CRYPTO) += virtio-crypto.o
+obj-$(CONFIG_VHOST_USER_FS) += vhost-user-fs.o
 obj-$(call land,$(CONFIG_VIRTIO_CRYPTO),$(CONFIG_VIRTIO_PCI)) += virtio-crypto-pci.o
 obj-$(CONFIG_VIRTIO_PMEM) += virtio-pmem.o
 common-obj-$(call land,$(CONFIG_VIRTIO_PMEM),$(CONFIG_VIRTIO_PCI)) += virtio-pmem-pci.o

hw/virtio/vhost-user-fs.c

@@ -0,0 +1,299 @@
+/*
+ * Vhost-user filesystem virtio device
+ *
+ * Copyright 2018-2019 Red Hat, Inc.
+ *
+ * Authors:
+ *  Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * (at your option) any later version.  See the COPYING file in the
+ * top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include <sys/ioctl.h>
+#include "standard-headers/linux/virtio_fs.h"
+#include "qapi/error.h"
+#include "hw/qdev-properties.h"
+#include "hw/virtio/virtio-bus.h"
+#include "hw/virtio/virtio-access.h"
+#include "qemu/error-report.h"
+#include "hw/virtio/vhost-user-fs.h"
+#include "monitor/monitor.h"
+
+static void vuf_get_config(VirtIODevice *vdev, uint8_t *config)
+{
+    VHostUserFS *fs = VHOST_USER_FS(vdev);
+    struct virtio_fs_config fscfg = {};
+
+    memcpy((char *)fscfg.tag, fs->conf.tag,
+           MIN(strlen(fs->conf.tag) + 1, sizeof(fscfg.tag)));
+
+    virtio_stl_p(vdev, &fscfg.num_request_queues, fs->conf.num_request_queues);
+
+    memcpy(config, &fscfg, sizeof(fscfg));
+}
+
+static void vuf_start(VirtIODevice *vdev)
+{
+    VHostUserFS *fs = VHOST_USER_FS(vdev);
+    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
+    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+    int ret;
+    int i;
+
+    if (!k->set_guest_notifiers) {
+        error_report("binding does not support guest notifiers");
+        return;
+    }
+
+    ret = vhost_dev_enable_notifiers(&fs->vhost_dev, vdev);
+    if (ret < 0) {
+        error_report("Error enabling host notifiers: %d", -ret);
+        return;
+    }
+
+    ret = k->set_guest_notifiers(qbus->parent, fs->vhost_dev.nvqs, true);
+    if (ret < 0) {
+        error_report("Error binding guest notifier: %d", -ret);
+        goto err_host_notifiers;
+    }
+
+    fs->vhost_dev.acked_features = vdev->guest_features;
+    ret = vhost_dev_start(&fs->vhost_dev, vdev);
+    if (ret < 0) {
+        error_report("Error starting vhost: %d", -ret);
+        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 < fs->vhost_dev.nvqs; i++) {
+        vhost_virtqueue_mask(&fs->vhost_dev, vdev, i, false);
+    }
+
+    return;
+
+err_guest_notifiers:
+    k->set_guest_notifiers(qbus->parent, fs->vhost_dev.nvqs, false);
+err_host_notifiers:
+    vhost_dev_disable_notifiers(&fs->vhost_dev, vdev);
+}
+
+static void vuf_stop(VirtIODevice *vdev)
+{
+    VHostUserFS *fs = VHOST_USER_FS(vdev);
+    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
+    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+    int ret;
+
+    if (!k->set_guest_notifiers) {
+        return;
+    }
+
+    vhost_dev_stop(&fs->vhost_dev, vdev);
+
+    ret = k->set_guest_notifiers(qbus->parent, fs->vhost_dev.nvqs, false);
+    if (ret < 0) {
+        error_report("vhost guest notifier cleanup failed: %d", ret);
+        return;
+    }
+
+    vhost_dev_disable_notifiers(&fs->vhost_dev, vdev);
+}
+
+static void vuf_set_status(VirtIODevice *vdev, uint8_t status)
+{
+    VHostUserFS *fs = VHOST_USER_FS(vdev);
+    bool should_start = status & VIRTIO_CONFIG_S_DRIVER_OK;
+
+    if (!vdev->vm_running) {
+        should_start = false;
+    }
+
+    if (fs->vhost_dev.started == should_start) {
+        return;
+    }
+
+    if (should_start) {
+        vuf_start(vdev);
+    } else {
+        vuf_stop(vdev);
+    }
+}
+
+static uint64_t vuf_get_features(VirtIODevice *vdev,
+                                      uint64_t requested_features,
+                                      Error **errp)
+{
+    /* No feature bits used yet */
+    return requested_features;
+}
+
+static void vuf_handle_output(VirtIODevice *vdev, VirtQueue *vq)
+{
+    /*
+     * Not normally called; it's the daemon that handles the queue;
+     * however virtio's cleanup path can call this.
+     */
+}
+
+static void vuf_guest_notifier_mask(VirtIODevice *vdev, int idx,
+                                            bool mask)
+{
+    VHostUserFS *fs = VHOST_USER_FS(vdev);
+
+    vhost_virtqueue_mask(&fs->vhost_dev, vdev, idx, mask);
+}
+
+static bool vuf_guest_notifier_pending(VirtIODevice *vdev, int idx)
+{
+    VHostUserFS *fs = VHOST_USER_FS(vdev);
+
+    return vhost_virtqueue_pending(&fs->vhost_dev, idx);
+}
+
+static void vuf_device_realize(DeviceState *dev, Error **errp)
+{
+    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+    VHostUserFS *fs = VHOST_USER_FS(dev);
+    unsigned int i;
+    size_t len;
+    int ret;
+
+    if (!fs->conf.chardev.chr) {
+        error_setg(errp, "missing chardev");
+        return;
+    }
+
+    if (!fs->conf.tag) {
+        error_setg(errp, "missing tag property");
+        return;
+    }
+    len = strlen(fs->conf.tag);
+    if (len == 0) {
+        error_setg(errp, "tag property cannot be empty");
+        return;
+    }
+    if (len > sizeof_field(struct virtio_fs_config, tag)) {
+        error_setg(errp, "tag property must be %zu bytes or less",
+                   sizeof_field(struct virtio_fs_config, tag));
+        return;
+    }
+
+    if (fs->conf.num_request_queues == 0) {
+        error_setg(errp, "num-request-queues property must be larger than 0");
+        return;
+    }
+
+    if (!is_power_of_2(fs->conf.queue_size)) {
+        error_setg(errp, "queue-size property must be a power of 2");
+        return;
+    }
+
+    if (fs->conf.queue_size > VIRTQUEUE_MAX_SIZE) {
+        error_setg(errp, "queue-size property must be %u or smaller",
+                   VIRTQUEUE_MAX_SIZE);
+        return;
+    }
+
+    if (!vhost_user_init(&fs->vhost_user, &fs->conf.chardev, errp)) {
+        return;
+    }
+
+    virtio_init(vdev, "vhost-user-fs", VIRTIO_ID_FS,
+                sizeof(struct virtio_fs_config));
+
+    /* Hiprio queue */
+    virtio_add_queue(vdev, fs->conf.queue_size, vuf_handle_output);
+
+    /* Request queues */
+    for (i = 0; i < fs->conf.num_request_queues; i++) {
+        virtio_add_queue(vdev, fs->conf.queue_size, vuf_handle_output);
+    }
+
+    /* 1 high prio queue, plus the number configured */
+    fs->vhost_dev.nvqs = 1 + fs->conf.num_request_queues;
+    fs->vhost_dev.vqs = g_new0(struct vhost_virtqueue, fs->vhost_dev.nvqs);
+    ret = vhost_dev_init(&fs->vhost_dev, &fs->vhost_user,
+                         VHOST_BACKEND_TYPE_USER, 0);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "vhost_dev_init failed");
+        goto err_virtio;
+    }
+
+    return;
+
+err_virtio:
+    vhost_user_cleanup(&fs->vhost_user);
+    virtio_cleanup(vdev);
+    g_free(fs->vhost_dev.vqs);
+    return;
+}
+
+static void vuf_device_unrealize(DeviceState *dev, Error **errp)
+{
+    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+    VHostUserFS *fs = VHOST_USER_FS(dev);
+
+    /* This will stop vhost backend if appropriate. */
+    vuf_set_status(vdev, 0);
+
+    vhost_dev_cleanup(&fs->vhost_dev);
+
+    vhost_user_cleanup(&fs->vhost_user);
+
+    virtio_cleanup(vdev);
+    g_free(fs->vhost_dev.vqs);
+    fs->vhost_dev.vqs = NULL;
+}
+
+static const VMStateDescription vuf_vmstate = {
+    .name = "vhost-user-fs",
+    .unmigratable = 1,
+};
+
+static Property vuf_properties[] = {
+    DEFINE_PROP_CHR("chardev", VHostUserFS, conf.chardev),
+    DEFINE_PROP_STRING("tag", VHostUserFS, conf.tag),
+    DEFINE_PROP_UINT16("num-request-queues", VHostUserFS,
+                       conf.num_request_queues, 1),
+    DEFINE_PROP_UINT16("queue-size", VHostUserFS, conf.queue_size, 128),
+    DEFINE_PROP_STRING("vhostfd", VHostUserFS, conf.vhostfd),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void vuf_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
+
+    dc->props = vuf_properties;
+    dc->vmsd = &vuf_vmstate;
+    set_bit(DEVICE_CATEGORY_STORAGE, dc->categories);
+    vdc->realize = vuf_device_realize;
+    vdc->unrealize = vuf_device_unrealize;
+    vdc->get_features = vuf_get_features;
+    vdc->get_config = vuf_get_config;
+    vdc->set_status = vuf_set_status;
+    vdc->guest_notifier_mask = vuf_guest_notifier_mask;
+    vdc->guest_notifier_pending = vuf_guest_notifier_pending;
+}
+
+static const TypeInfo vuf_info = {
+    .name = TYPE_VHOST_USER_FS,
+    .parent = TYPE_VIRTIO_DEVICE,
+    .instance_size = sizeof(VHostUserFS),
+    .class_init = vuf_class_init,
+};
+
+static void vuf_register_types(void)
+{
+    type_register_static(&vuf_info);
+}
+
+type_init(vuf_register_types)

include/hw/virtio/vhost-user-fs.h

@@ -0,0 +1,45 @@
+/*
+ * Vhost-user filesystem virtio device
+ *
+ * Copyright 2018-2019 Red Hat, Inc.
+ *
+ * Authors:
+ *  Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * (at your option) any later version.  See the COPYING file in the
+ * top-level directory.
+ */
+
+#ifndef _QEMU_VHOST_USER_FS_H
+#define _QEMU_VHOST_USER_FS_H
+
+#include "hw/virtio/virtio.h"
+#include "hw/virtio/vhost.h"
+#include "hw/virtio/vhost-user.h"
+#include "chardev/char-fe.h"
+
+#define TYPE_VHOST_USER_FS "vhost-user-fs-device"
+#define VHOST_USER_FS(obj) \
+        OBJECT_CHECK(VHostUserFS, (obj), TYPE_VHOST_USER_FS)
+
+typedef struct {
+    CharBackend chardev;
+    char *tag;
+    uint16_t num_request_queues;
+    uint16_t queue_size;
+    char *vhostfd;
+} VHostUserFSConf;
+
+typedef struct {
+    /*< private >*/
+    VirtIODevice parent;
+    VHostUserFSConf conf;
+    struct vhost_virtqueue *vhost_vqs;
+    struct vhost_dev vhost_dev;
+    VhostUserState vhost_user;
+
+    /*< public >*/
+} VHostUserFS;
+
+#endif /* _QEMU_VHOST_USER_FS_H */