On 6/10/25 13:42, Mark Cave-Ayland wrote:
On 07/06/2025 01:10, John Levon wrote:

Introduce basic plumbing for vfio-user behind a new
--enable-vfio-user-client option.

We introduce VFIOUserContainer in hw/vfio-user/container.c, which is a
container type for the "IOMMU" type "vfio-iommu-user", and share some
common container code from hw/vfio/container.c.

Add hw/vfio-user/pci.c for instantiating VFIOUserPCIDevice objects,
sharing some common code from hw/vfio/pci.c.

Originally-by: John Johnson <john.g.john...@oracle.com>
Signed-off-by: Elena Ufimtseva <elena.ufimts...@oracle.com>
Signed-off-by: Jagannathan Raman <jag.ra...@oracle.com>
Signed-off-by: John Levon <john.le...@nutanix.com>
---
  MAINTAINERS                           |   2 +
  hw/vfio-user/container.h              |  25 +++
  include/hw/vfio/vfio-container-base.h |   1 +
  hw/vfio-user/container.c              | 212 ++++++++++++++++++++++++++
  hw/vfio-user/pci.c                    | 155 +++++++++++++++++++
  hw/meson.build                        |   1 +
  hw/vfio-user/meson.build              |   9 ++
  meson_options.txt                     |   2 +
  scripts/meson-buildoptions.sh         |   4 +
  9 files changed, 411 insertions(+)
  create mode 100644 hw/vfio-user/container.h
  create mode 100644 hw/vfio-user/container.c
  create mode 100644 hw/vfio-user/pci.c
  create mode 100644 hw/vfio-user/meson.build

diff --git a/MAINTAINERS b/MAINTAINERS
index dbc393989a..328bab8d19 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4252,6 +4252,8 @@ M: John Levon <john.le...@nutanix.com>
  M: Thanos Makatos <thanos.maka...@nutanix.com>
  S: Supported
  F: docs/devel/vfio-user.rst
+F: hw/vfio-user/*
+F: include/hw/vfio-user/*
  F: subprojects/libvfio-user

Question: how do you see the division between hw/vfio and hw/vfio-user? My 
initial feeling is that there is substantial sharing between the two, in which 
case I'd expect the files to be in hw/vfio as e.g. hw/vfio/container-user.c 
etc. instead of its own directory.

Cédric, what are your thoughts here?

The vfio devices are very dependent on the bus they depend on.
My idea is to keep under hw/vfio the initial implementation of
the vfio-pci device and the common services for other "complex"
vfio devices like vfio-user-pci. Which give us :

        hw/vfio/*               17323 lines
        hw/vfio-user/*          2955 lines

vfio-ap and vfio-ccw are small but I might still move them under
s390x. vfio-platform will be removed in the next QEMU cycle.

Also, util/vfio-helpers.c, on which is built the nvme BlockDriver,
should be merged under the common services, so under hw/vfio.


Thanks,

C.




  EBPF:
diff --git a/hw/vfio-user/container.h b/hw/vfio-user/container.h
new file mode 100644
index 0000000000..3cd3303e68
--- /dev/null
+++ b/hw/vfio-user/container.h
@@ -0,0 +1,25 @@
+/*
+ * vfio-user specific definitions.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef HW_VFIO_USER_CONTAINER_H
+#define HW_VFIO_USER_CONTAINER_H
+
+#include <inttypes.h>
+#include <stdbool.h>

These shouldn't be included directly: you probably just want:

#include "qemu/osdep.h"

instead.

+#include "hw/vfio/vfio-container-base.h"
+
+/* MMU container sub-class for vfio-user. */
+typedef struct VFIOUserContainer {
+    VFIOContainerBase bcontainer;
+} VFIOUserContainer;
+
+OBJECT_DECLARE_SIMPLE_TYPE(VFIOUserContainer, VFIO_IOMMU_USER);

As per the documentation at 
https://qemu-project.gitlab.io/qemu/devel/style.html#qemu-object-model-declarations
 the parent object should always be named parent_obj and struct shouldn't have 
a typedef i.e.

/* MMU container sub-class for vfio-user. */
struct VFIOUserContainer {
     VFIOContainerBase parent_obj;
};

OBJECT_DECLARE_SIMPLE_TYPE(VFIOUserContainer, VFIO_IOMMU_USER);

+#endif /* HW_VFIO_USER_CONTAINER_H */
diff --git a/include/hw/vfio/vfio-container-base.h 
b/include/hw/vfio/vfio-container-base.h
index 9d37f86115..28899ca0a6 100644
--- a/include/hw/vfio/vfio-container-base.h
+++ b/include/hw/vfio/vfio-container-base.h
@@ -109,6 +109,7 @@ vfio_container_get_page_size_mask(const VFIOContainerBase 
*bcontainer)
  #define TYPE_VFIO_IOMMU_LEGACY TYPE_VFIO_IOMMU "-legacy"
  #define TYPE_VFIO_IOMMU_SPAPR TYPE_VFIO_IOMMU "-spapr"
  #define TYPE_VFIO_IOMMU_IOMMUFD TYPE_VFIO_IOMMU "-iommufd"
+#define TYPE_VFIO_IOMMU_USER TYPE_VFIO_IOMMU "-user"
  OBJECT_DECLARE_TYPE(VFIOContainerBase, VFIOIOMMUClass, VFIO_IOMMU)
diff --git a/hw/vfio-user/container.c b/hw/vfio-user/container.c
new file mode 100644
index 0000000000..2892845b4f
--- /dev/null
+++ b/hw/vfio-user/container.c
@@ -0,0 +1,212 @@
+/*
+ * Container for vfio-user IOMMU type: rather than communicating with the 
kernel
+ * vfio driver, we communicate over a socket to a server using the vfio-user
+ * protocol.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include <sys/ioctl.h>
+#include <linux/vfio.h>
+#include "qemu/osdep.h"
+
+#include "hw/vfio-user/container.h"
+#include "hw/vfio/vfio-cpr.h"
+#include "hw/vfio/vfio-device.h"
+#include "hw/vfio/vfio-listener.h"
+#include "qapi/error.h"
+#include "trace.h"
+
+static int vfio_user_dma_unmap(const VFIOContainerBase *bcontainer,
+                               hwaddr iova, ram_addr_t size,
+                               IOMMUTLBEntry *iotlb, bool unmap_all)
+{
+    return -ENOTSUP;
+}
+
+static int vfio_user_dma_map(const VFIOContainerBase *bcontainer, hwaddr iova,
+                             ram_addr_t size, void *vaddr, bool readonly,
+                             MemoryRegion *mrp)
+{
+    return -ENOTSUP;
+}
+
+static int
+vfio_user_set_dirty_page_tracking(const VFIOContainerBase *bcontainer,
+                                    bool start, Error **errp)
+{
+    error_setg_errno(errp, ENOTSUP, "Not supported");
+    return -ENOTSUP;
+}
+
+static int vfio_user_query_dirty_bitmap(const VFIOContainerBase *bcontainer,
+                                         VFIOBitmap *vbmap, hwaddr iova,
+                                         hwaddr size, Error **errp)
+{
+    error_setg_errno(errp, ENOTSUP, "Not supported");
+    return -ENOTSUP;
+}
+
+static bool vfio_user_setup(VFIOContainerBase *bcontainer, Error **errp)
+{
+    error_setg_errno(errp, ENOTSUP, "Not supported");
+    return -ENOTSUP;
+}
+
+static VFIOUserContainer *vfio_user_create_container(Error **errp)
+{
+    VFIOUserContainer *container;
+
+    container = VFIO_IOMMU_USER(object_new(TYPE_VFIO_IOMMU_USER));
+    return container;
+}
+
+/*
+ * Try to mirror vfio_container_connect() as much as possible.
+ */
+static VFIOUserContainer *
+vfio_user_container_connect(AddressSpace *as, Error **errp)
+{
+    VFIOContainerBase *bcontainer;
+    VFIOUserContainer *container;
+    VFIOAddressSpace *space;
+    VFIOIOMMUClass *vioc;
+
+    space = vfio_address_space_get(as);
+
+    container = vfio_user_create_container(errp);
+    if (!container) {
+        goto put_space_exit;
+    }
+
+    bcontainer = &container->bcontainer;

References to the object hierarchy should always be done with the automatically 
generated QOM cast macros since they are easier to read, and also ensure type 
safety e.g.:

        bcontainer = VFIO_IOMMU(container);

+    if (!vfio_cpr_register_container(bcontainer, errp)) {
+        goto free_container_exit;
+    }
+
+    vioc = VFIO_IOMMU_GET_CLASS(bcontainer);
+    assert(vioc->setup);
+
+    if (!vioc->setup(bcontainer, errp)) {
+        goto unregister_container_exit;
+    }
+
+    vfio_address_space_insert(space, bcontainer);
+
+    if (!vfio_listener_register(bcontainer, errp)) {
+        goto listener_release_exit;
+    }
+
+    bcontainer->initialized = true;
+
+    return container;
+
+listener_release_exit:
+    vfio_listener_unregister(bcontainer);
+    if (vioc->release) {
+        vioc->release(bcontainer);
+    }
+
+unregister_container_exit:
+    vfio_cpr_unregister_container(bcontainer);
+
+free_container_exit:
+    object_unref(container);
+
+put_space_exit:
+    vfio_address_space_put(space);
+
+    return NULL;
+}
+
+static void vfio_user_container_disconnect(VFIOUserContainer *container)
+{
+    VFIOContainerBase *bcontainer = &container->bcontainer;

Use a QOM cast here.

+    VFIOIOMMUClass *vioc = VFIO_IOMMU_GET_CLASS(bcontainer);
+
+    vfio_listener_unregister(bcontainer);
+    if (vioc->release) {
+        vioc->release(bcontainer);
+    }
+
+    VFIOAddressSpace *space = bcontainer->space;
+
+    vfio_cpr_unregister_container(bcontainer);
+    object_unref(container);
+
+    vfio_address_space_put(space);
+}
+
+static bool vfio_user_device_get(VFIOUserContainer *container,
+                                 VFIODevice *vbasedev, Error **errp)
+{
+    struct vfio_device_info info = { 0 };
+
+    vbasedev->fd = -1;
+
+    vfio_device_prepare(vbasedev, &container->bcontainer, &info);

Use a QOM cast here.

+    return true;
+}
+
+/*
+ * vfio_user_device_attach: attach a device to a new container.
+ */
+static bool vfio_user_device_attach(const char *name, VFIODevice *vbasedev,
+                                    AddressSpace *as, Error **errp)
+{
+    VFIOUserContainer *container;
+
+    container = vfio_user_container_connect(as, errp);
+    if (container == NULL) {
+        error_prepend(errp, "failed to connect proxy");
+        return false;
+    }
+
+    return vfio_user_device_get(container, vbasedev, errp);
+}
+
+static void vfio_user_device_detach(VFIODevice *vbasedev)
+{
+    VFIOUserContainer *container = container_of(vbasedev->bcontainer,
+                                                VFIOUserContainer, bcontainer);
+
+    vfio_device_unprepare(vbasedev);
+
+    vfio_user_container_disconnect(container);
+}
+
+static int vfio_user_pci_hot_reset(VFIODevice *vbasedev, bool single)
+{
+    /* ->needs_reset is always false for vfio-user. */
+    return 0;
+}
+
+static void vfio_iommu_user_class_init(ObjectClass *klass, const void *data)
+{
+    VFIOIOMMUClass *vioc = VFIO_IOMMU_CLASS(klass);
+
+    vioc->setup = vfio_user_setup;
+    vioc->dma_map = vfio_user_dma_map;
+    vioc->dma_unmap = vfio_user_dma_unmap;
+    vioc->attach_device = vfio_user_device_attach;
+    vioc->detach_device = vfio_user_device_detach;
+    vioc->set_dirty_page_tracking = vfio_user_set_dirty_page_tracking;
+    vioc->query_dirty_bitmap = vfio_user_query_dirty_bitmap;
+    vioc->pci_hot_reset = vfio_user_pci_hot_reset;
+};
+
+static const TypeInfo types[] = {
+    {
+        .name = TYPE_VFIO_IOMMU_USER,
+        .parent = TYPE_VFIO_IOMMU,
+        .instance_size = sizeof(VFIOUserContainer),
+        .class_init = vfio_iommu_user_class_init,
+    },
+};
+
+DEFINE_TYPES(types)
diff --git a/hw/vfio-user/pci.c b/hw/vfio-user/pci.c
new file mode 100644
index 0000000000..74b0c61f9b
--- /dev/null
+++ b/hw/vfio-user/pci.c
@@ -0,0 +1,155 @@
+/*
+ * vfio PCI device over a UNIX socket.
+ *
+ * Copyright © 2018, 2021 Oracle and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include <sys/ioctl.h>
+#include "qemu/osdep.h"
+
+#include "hw/qdev-properties.h"
+#include "hw/vfio/pci.h"
+
+#define TYPE_VFIO_USER_PCI "vfio-user-pci"
+OBJECT_DECLARE_SIMPLE_TYPE(VFIOUserPCIDevice, VFIO_USER_PCI)
+
+struct VFIOUserPCIDevice {
+    VFIOPCIDevice device;
+    char *sock_name;
+};

Again as per the documentation link above, device should be called parent_obj 
plus there should be a empty line between parent_obj and the other members i.e.

struct VFIOUserPCIDevice {
     VFIOPCIDevice parent_obj;

     char *sock_name;
}

Note that by using QOM casts the name of the parent object member is not 
exposed to the remainder of the code.

+/*
+ * Emulated devices don't use host hot reset
+ */
+static void vfio_user_compute_needs_reset(VFIODevice *vbasedev)
+{
+    vbasedev->needs_reset = false;
+}
+
+static Object *vfio_user_pci_get_object(VFIODevice *vbasedev)
+{
+    VFIOUserPCIDevice *vdev = container_of(vbasedev, VFIOUserPCIDevice,
+                                           device.vbasedev);

Hmmm. Not for this series but this may suggest VFIODevice should be QOMified.

+    return OBJECT(vdev);
+}
 >   > +static VFIODeviceOps vfio_user_pci_ops = {
+    .vfio_compute_needs_reset = vfio_user_compute_needs_reset,
+    .vfio_eoi = vfio_pci_intx_eoi,
+    .vfio_get_object = vfio_user_pci_get_object,
+    /* No live migration support yet. */
+    .vfio_save_config = NULL,
+    .vfio_load_config = NULL,
+};
+
+static void vfio_user_pci_realize(PCIDevice *pdev, Error **errp)
+{
+    ERRP_GUARD();
+    VFIOUserPCIDevice *udev = VFIO_USER_PCI(pdev);
+    VFIOPCIDevice *vdev = VFIO_PCI_BASE(pdev);
+    VFIODevice *vbasedev = &vdev->vbasedev;
+    AddressSpace *as;
+
+    /*
+     * TODO: make option parser understand SocketAddress
+     * and use that instead of having scalar options
+     * for each socket type.
+     */
+    if (!udev->sock_name) {
+        error_setg(errp, "No socket specified");
+        error_append_hint(errp, "Use -device vfio-user-pci,socket=<name>\n");
+        return;
+    }
+
+    vbasedev->name = g_strdup_printf("VFIO user <%s>", udev->sock_name);
+
+    /*
+     * vfio-user devices are effectively mdevs (don't use a host iommu).
+     */
+    vbasedev->mdev = true;
+
+    as = pci_device_iommu_address_space(pdev);
+    if (!vfio_device_attach_by_iommu_type(TYPE_VFIO_IOMMU_USER,
+                                          vbasedev->name, vbasedev,
+                                          as, errp)) {
+        error_prepend(errp, VFIO_MSG_PREFIX, vbasedev->name);
+        return;
+    }
+}
+
+static void vfio_user_instance_init(Object *obj)
+{
+    PCIDevice *pci_dev = PCI_DEVICE(obj);
+    VFIOPCIDevice *vdev = VFIO_PCI_BASE(obj);
+    VFIODevice *vbasedev = &vdev->vbasedev;
+
+    device_add_bootindex_property(obj, &vdev->bootindex,
+                                  "bootindex", NULL,
+                                  &pci_dev->qdev);
+    vdev->host.domain = ~0U;
+    vdev->host.bus = ~0U;
+    vdev->host.slot = ~0U;
+    vdev->host.function = ~0U;
+
+    vfio_device_init(vbasedev, VFIO_DEVICE_TYPE_PCI, &vfio_user_pci_ops,
+                     DEVICE(vdev), false);
+
+    vdev->nv_gpudirect_clique = 0xFF;
+
+    /*
+     * QEMU_PCI_CAP_EXPRESS initialization does not depend on QEMU command
+     * line, therefore, no need to wait to realize like other devices.
+     */
+    pci_dev->cap_present |= QEMU_PCI_CAP_EXPRESS;
+}
+
+static void vfio_user_instance_finalize(Object *obj)
+{
+    VFIOPCIDevice *vdev = VFIO_PCI_BASE(obj);
+
+    vfio_pci_put_device(vdev);
+}
+
+static const Property vfio_user_pci_dev_properties[] = {
+    DEFINE_PROP_UINT32("x-pci-vendor-id", VFIOPCIDevice,
+                       vendor_id, PCI_ANY_ID),
+    DEFINE_PROP_UINT32("x-pci-device-id", VFIOPCIDevice,
+                       device_id, PCI_ANY_ID),
+    DEFINE_PROP_UINT32("x-pci-sub-vendor-id", VFIOPCIDevice,
+                       sub_vendor_id, PCI_ANY_ID),
+    DEFINE_PROP_UINT32("x-pci-sub-device-id", VFIOPCIDevice,
+                       sub_device_id, PCI_ANY_ID),
+    DEFINE_PROP_STRING("socket", VFIOUserPCIDevice, sock_name),
+};
+
+static void vfio_user_pci_dev_class_init(ObjectClass *klass, const void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    PCIDeviceClass *pdc = PCI_DEVICE_CLASS(klass);
+
+    device_class_set_props(dc, vfio_user_pci_dev_properties);
+    dc->desc = "VFIO over socket PCI device assignment";
+    pdc->realize = vfio_user_pci_realize;
+}
+
+static const TypeInfo vfio_user_pci_dev_info = {
+    .name = TYPE_VFIO_USER_PCI,
+    .parent = TYPE_VFIO_PCI_BASE,
+    .instance_size = sizeof(VFIOUserPCIDevice),
+    .class_init = vfio_user_pci_dev_class_init,
+    .instance_init = vfio_user_instance_init,
+    .instance_finalize = vfio_user_instance_finalize,
+};
+
+static void register_vfio_user_dev_type(void)
+{
+    type_register_static(&vfio_user_pci_dev_info);
+}
+
+ type_init(register_vfio_user_dev_type)

Use DEFINE_TYPES as you've already done above instead of type_init() here.

diff --git a/hw/meson.build b/hw/meson.build
index b91f761fe0..791ce21ab4 100644
--- a/hw/meson.build
+++ b/hw/meson.build
@@ -39,6 +39,7 @@ subdir('uefi')
  subdir('ufs')
  subdir('usb')
  subdir('vfio')
+subdir('vfio-user')
  subdir('virtio')
  subdir('vmapple')
  subdir('watchdog')
diff --git a/hw/vfio-user/meson.build b/hw/vfio-user/meson.build
new file mode 100644
index 0000000000..f1fee70c85
--- /dev/null
+++ b/hw/vfio-user/meson.build
@@ -0,0 +1,9 @@
+vfio_user_ss = ss.source_set()
+vfio_user_ss.add(files(
+  'container.c',
+  'pci.c',
+))
+
+if get_option('vfio_user_client').enabled()
+  specific_ss.add_all(vfio_user_ss)
+endif
diff --git a/meson_options.txt b/meson_options.txt
index a442be2995..97d3db44cd 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -109,6 +109,8 @@ option('multiprocess', type: 'feature', value: 'auto',
         description: 'Out of process device emulation support')
  option('relocatable', type : 'boolean', value : true,
         description: 'toggle relocatable install')
+option('vfio_user_client', type: 'feature', value: 'disabled',
+       description: 'vfio-user client support')
  option('vfio_user_server', type: 'feature', value: 'disabled',
         description: 'vfio-user server support')
  option('dbus_display', type: 'feature', value: 'auto',
diff --git a/scripts/meson-buildoptions.sh b/scripts/meson-buildoptions.sh
index f09ef9604f..2c5673769a 100644
--- a/scripts/meson-buildoptions.sh
+++ b/scripts/meson-buildoptions.sh
@@ -201,6 +201,8 @@ meson_options_help() {
    printf "%s\n" '  vdi             vdi image format support'
    printf "%s\n" '  vduse-blk-export'
    printf "%s\n" '                  VDUSE block export support'
+  printf "%s\n" '  vfio-user-client'
+  printf "%s\n" '                  vfio-user client support'
    printf "%s\n" '  vfio-user-server'
    printf "%s\n" '                  vfio-user server support'
    printf "%s\n" '  vhdx            vhdx image format support'
@@ -529,6 +531,8 @@ _meson_option_parse() {
      --disable-vdi) printf "%s" -Dvdi=disabled ;;
      --enable-vduse-blk-export) printf "%s" -Dvduse_blk_export=enabled ;;
      --disable-vduse-blk-export) printf "%s" -Dvduse_blk_export=disabled ;;
+    --enable-vfio-user-client) printf "%s" -Dvfio_user_client=enabled ;;
+    --disable-vfio-user-client) printf "%s" -Dvfio_user_client=disabled ;;
      --enable-vfio-user-server) printf "%s" -Dvfio_user_server=enabled ;;
      --disable-vfio-user-server) printf "%s" -Dvfio_user_server=disabled ;;
      --enable-vhdx) printf "%s" -Dvhdx=enabled ;;


ATB,

Mark.



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