Re: [PATCH v6 01/21] backends/iommufd: Introduce the iommufd object

[Eric Auger <eric.auger@redhat.com>]

Hi Zhenzhong,

On 11/14/23 11:09, Zhenzhong Duan wrote:
> From: Eric Auger <eric.auger@redhat.com>
>
> Introduce an iommufd object which allows the interaction
> with the host /dev/iommu device.
>
> The /dev/iommu can have been already pre-opened outside of qemu,
> in which case the fd can be passed directly along with the
> iommufd object:
>
> This allows the iommufd object to be shared accross several
> subsystems (VFIO, VDPA, ...). For example, libvirt would open
> the /dev/iommu once.
>
> If no fd is passed along with the iommufd object, the /dev/iommu
> is opened by the qemu code.
>
> Suggested-by: Alex Williamson <alex.williamson@redhat.com>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> ---
> v6: remove redundant call, alloc_hwpt, get/put_ioas
>
>  MAINTAINERS              |   7 ++
>  qapi/qom.json            |  19 ++++
>  include/sysemu/iommufd.h |  44 ++++++++
>  backends/iommufd.c       | 228 +++++++++++++++++++++++++++++++++++++++
>  backends/Kconfig         |   4 +
>  backends/meson.build     |   1 +
>  backends/trace-events    |  10 ++
>  qemu-options.hx          |  12 +++
>  8 files changed, 325 insertions(+)
>  create mode 100644 include/sysemu/iommufd.h
>  create mode 100644 backends/iommufd.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index ff1238bb98..a4891f7bda 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -2166,6 +2166,13 @@ F: hw/vfio/ap.c
>  F: docs/system/s390x/vfio-ap.rst
>  L: qemu-s390x@nongnu.org
>  
> +iommufd
> +M: Yi Liu <yi.l.liu@intel.com>
> +M: Eric Auger <eric.auger@redhat.com>
Zhenzhong, don't you want to be added here?
> +S: Supported
> +F: backends/iommufd.c
> +F: include/sysemu/iommufd.h
> +
>  vhost
>  M: Michael S. Tsirkin <mst@redhat.com>
>  S: Supported
> diff --git a/qapi/qom.json b/qapi/qom.json
> index c53ef978ff..1fd8555a75 100644
> --- a/qapi/qom.json
> +++ b/qapi/qom.json
> @@ -794,6 +794,23 @@
>  { 'struct': 'VfioUserServerProperties',
>    'data': { 'socket': 'SocketAddress', 'device': 'str' } }
>  
> +##
> +# @IOMMUFDProperties:
> +#
> +# Properties for iommufd objects.
> +#
> +# @fd: file descriptor name previously passed via 'getfd' command,

"previously passed via 'getfd' command", I wonder if this applies here or whether it is copy/paste of 
RemoteObjectProperties.fd doc?

> +#     which represents a pre-opened /dev/iommu.  This allows the
> +#     iommufd object to be shared accross several subsystems
> +#     (VFIO, VDPA, ...), and the file descriptor to be shared
> +#     with other process, e.g. DPDK.  (default: QEMU opens
> +#     /dev/iommu by itself)
> +#
> +# Since: 8.2
> +##
> +{ 'struct': 'IOMMUFDProperties',
> +  'data': { '*fd': 'str' } }
> +
>  ##
>  # @RngProperties:
>  #
> @@ -934,6 +951,7 @@
>      'input-barrier',
>      { 'name': 'input-linux',
>        'if': 'CONFIG_LINUX' },
> +    'iommufd',
>      'iothread',
>      'main-loop',
>      { 'name': 'memory-backend-epc',
> @@ -1003,6 +1021,7 @@
>        'input-barrier':              'InputBarrierProperties',
>        'input-linux':                { 'type': 'InputLinuxProperties',
>                                        'if': 'CONFIG_LINUX' },
> +      'iommufd':                    'IOMMUFDProperties',
>        'iothread':                   'IothreadProperties',
>        'main-loop':                  'MainLoopProperties',
>        'memory-backend-epc':         { 'type': 'MemoryBackendEpcProperties',
> diff --git a/include/sysemu/iommufd.h b/include/sysemu/iommufd.h
> new file mode 100644
> index 0000000000..9b3a86f57d
> --- /dev/null
> +++ b/include/sysemu/iommufd.h
> @@ -0,0 +1,44 @@
> +#ifndef SYSEMU_IOMMUFD_H
> +#define SYSEMU_IOMMUFD_H
> +
> +#include "qom/object.h"
> +#include "qemu/thread.h"
> +#include "exec/hwaddr.h"
> +#include "exec/cpu-common.h"
> +
> +#define TYPE_IOMMUFD_BACKEND "iommufd"
> +OBJECT_DECLARE_TYPE(IOMMUFDBackend, IOMMUFDBackendClass,
> +                    IOMMUFD_BACKEND)
> +#define IOMMUFD_BACKEND(obj) \
> +    OBJECT_CHECK(IOMMUFDBackend, (obj), TYPE_IOMMUFD_BACKEND)
> +#define IOMMUFD_BACKEND_GET_CLASS(obj) \
> +    OBJECT_GET_CLASS(IOMMUFDBackendClass, (obj), TYPE_IOMMUFD_BACKEND)
> +#define IOMMUFD_BACKEND_CLASS(klass) \
> +    OBJECT_CLASS_CHECK(IOMMUFDBackendClass, (klass), TYPE_IOMMUFD_BACKEND)
> +struct IOMMUFDBackendClass {
> +    ObjectClass parent_class;
> +};
> +
> +struct IOMMUFDBackend {
> +    Object parent;
> +
> +    /*< protected >*/
> +    int fd;            /* /dev/iommu file descriptor */
> +    bool owned;        /* is the /dev/iommu opened internally */
> +    QemuMutex lock;
> +    uint32_t users;
> +
> +    /*< public >*/
> +};
> +
> +int iommufd_backend_connect(IOMMUFDBackend *be, Error **errp);
> +void iommufd_backend_disconnect(IOMMUFDBackend *be);
> +
> +int iommufd_backend_alloc_ioas(IOMMUFDBackend *be, uint32_t *ioas_id,
> +                               Error **errp);
> +void iommufd_backend_free_id(IOMMUFDBackend *be, uint32_t id);
> +int iommufd_backend_map_dma(IOMMUFDBackend *be, uint32_t ioas_id, hwaddr iova,
> +                            ram_addr_t size, void *vaddr, bool readonly);
> +int iommufd_backend_unmap_dma(IOMMUFDBackend *be, uint32_t ioas_id,
> +                              hwaddr iova, ram_addr_t size);
> +#endif
> diff --git a/backends/iommufd.c b/backends/iommufd.c
> new file mode 100644
> index 0000000000..ea3e2a8f85
> --- /dev/null
> +++ b/backends/iommufd.c
> @@ -0,0 +1,228 @@
> +/*
> + * iommufd container backend
> + *
> + * Copyright (C) 2023 Intel Corporation.
> + * Copyright Red Hat, Inc. 2023
> + *
> + * Authors: Yi Liu <yi.l.liu@intel.com>
> + *          Eric Auger <eric.auger@redhat.com>
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#include "qemu/osdep.h"
> +#include "sysemu/iommufd.h"
> +#include "qapi/error.h"
> +#include "qapi/qmp/qerror.h"
> +#include "qemu/module.h"
> +#include "qom/object_interfaces.h"
> +#include "qemu/error-report.h"
> +#include "monitor/monitor.h"
> +#include "trace.h"
> +#include <sys/ioctl.h>
> +#include <linux/iommufd.h>
> +
> +static void iommufd_backend_init(Object *obj)
> +{
> +    IOMMUFDBackend *be = IOMMUFD_BACKEND(obj);
> +
> +    be->fd = -1;
> +    be->users = 0;
> +    be->owned = true;
> +    qemu_mutex_init(&be->lock);
> +}
> +
> +static void iommufd_backend_finalize(Object *obj)
> +{
> +    IOMMUFDBackend *be = IOMMUFD_BACKEND(obj);
> +
> +    if (be->owned) {
> +        close(be->fd);
> +        be->fd = -1;
> +    }
> +}
> +
> +static void iommufd_backend_set_fd(Object *obj, const char *str, Error **errp)
> +{
> +    IOMMUFDBackend *be = IOMMUFD_BACKEND(obj);
> +    int fd = -1;
> +
> +    fd = monitor_fd_param(monitor_cur(), str, errp);
> +    if (fd == -1) {
> +        error_prepend(errp, "Could not parse remote object fd %s:", str);
> +        return;
> +    }
> +    qemu_mutex_lock(&be->lock);
> +    be->fd = fd;
> +    be->owned = false;
> +    qemu_mutex_unlock(&be->lock);
> +    trace_iommu_backend_set_fd(be->fd);
> +}
> +
> +static void iommufd_backend_class_init(ObjectClass *oc, void *data)
> +{
> +    object_class_property_add_str(oc, "fd", NULL, iommufd_backend_set_fd);
> +}
> +
> +int iommufd_backend_connect(IOMMUFDBackend *be, Error **errp)
> +{
> +    int fd, ret = 0;
> +
> +    qemu_mutex_lock(&be->lock);
> +    if (be->users == UINT32_MAX) {
> +        error_setg(errp, "too many connections");
> +        ret = -E2BIG;
> +        goto out;
> +    }
> +    if (be->owned && !be->users) {
> +        fd = qemu_open_old("/dev/iommu", O_RDWR);
> +        if (fd < 0) {
> +            error_setg_errno(errp, errno, "/dev/iommu opening failed");
> +            ret = fd;
> +            goto out;
> +        }
> +        be->fd = fd;
> +    }
> +    be->users++;
> +out:
> +    trace_iommufd_backend_connect(be->fd, be->owned,
> +                                  be->users, ret);
> +    qemu_mutex_unlock(&be->lock);
> +    return ret;
> +}
> +
> +void iommufd_backend_disconnect(IOMMUFDBackend *be)
> +{
> +    qemu_mutex_lock(&be->lock);
> +    if (!be->users) {
> +        goto out;
> +    }
> +    be->users--;
> +    if (!be->users && be->owned) {
> +        close(be->fd);
> +        be->fd = -1;
> +    }
> +out:
> +    trace_iommufd_backend_disconnect(be->fd, be->users);
> +    qemu_mutex_unlock(&be->lock);
> +}
> +
> +int iommufd_backend_alloc_ioas(IOMMUFDBackend *be, uint32_t *ioas_id,
> +                               Error **errp)
> +{
> +    int ret, fd = be->fd;
> +    struct iommu_ioas_alloc alloc_data  = {
> +        .size = sizeof(alloc_data),
> +        .flags = 0,
> +    };
> +
> +    ret = ioctl(fd, IOMMU_IOAS_ALLOC, &alloc_data);
> +    if (ret) {
> +        error_setg_errno(errp, errno, "Failed to allocate ioas");
> +        return ret;
> +    }
> +
> +    *ioas_id = alloc_data.out_ioas_id;
> +    trace_iommufd_backend_alloc_ioas(fd, *ioas_id, ret);
> +
> +    return ret;
> +}
> +
> +void iommufd_backend_free_id(IOMMUFDBackend *be, uint32_t id)
> +{
> +    int ret, fd = be->fd;
> +    struct iommu_destroy des = {
> +        .size = sizeof(des),
> +        .id = id,
> +    };
> +
> +    ret = ioctl(fd, IOMMU_DESTROY, &des);
> +    trace_iommufd_backend_free_id(fd, id, ret);
> +    if (ret) {
> +        error_report("Failed to free id: %u %m", id);
> +    }
> +}
> +
> +int iommufd_backend_map_dma(IOMMUFDBackend *be, uint32_t ioas_id, hwaddr iova,
> +                            ram_addr_t size, void *vaddr, bool readonly)
> +{
> +    int ret, fd = be->fd;
> +    struct iommu_ioas_map map = {
> +        .size = sizeof(map),
> +        .flags = IOMMU_IOAS_MAP_READABLE |
> +                 IOMMU_IOAS_MAP_FIXED_IOVA,
> +        .ioas_id = ioas_id,
> +        .__reserved = 0,
> +        .user_va = (uintptr_t)vaddr,
> +        .iova = iova,
> +        .length = size,
> +    };
> +
> +    if (!readonly) {
> +        map.flags |= IOMMU_IOAS_MAP_WRITEABLE;
> +    }
> +
> +    ret = ioctl(fd, IOMMU_IOAS_MAP, &map);
> +    trace_iommufd_backend_map_dma(fd, ioas_id, iova, size,
> +                                  vaddr, readonly, ret);
> +    if (ret) {
> +        ret = -errno;
> +        error_report("IOMMU_IOAS_MAP failed: %m");
> +    }
> +    return ret;
> +}
> +
> +int iommufd_backend_unmap_dma(IOMMUFDBackend *be, uint32_t ioas_id,
> +                              hwaddr iova, ram_addr_t size)
> +{
> +    int ret, fd = be->fd;
> +    struct iommu_ioas_unmap unmap = {
> +        .size = sizeof(unmap),
> +        .ioas_id = ioas_id,
> +        .iova = iova,
> +        .length = size,
> +    };
> +
> +    ret = ioctl(fd, IOMMU_IOAS_UNMAP, &unmap);
> +    /*
> +     * IOMMUFD takes mapping as some kind of object, unmapping
> +     * nonexistent mapping is treated as deleting a nonexistent
> +     * object and return ENOENT. This is different from legacy
> +     * backend which allows it. vIOMMU may trigger a lot of
> +     * redundant unmapping, to avoid flush the log, treat them
> +     * as succeess for IOMMUFD just like legacy backend.
> +     */
> +    if (ret && errno == ENOENT) {
> +        trace_iommufd_backend_unmap_dma_non_exist(fd, ioas_id, iova, size, ret);
> +        ret = 0;
> +    } else {
> +        trace_iommufd_backend_unmap_dma(fd, ioas_id, iova, size, ret);
> +    }
> +
> +    if (ret) {
> +        ret = -errno;
> +        error_report("IOMMU_IOAS_UNMAP failed: %m");
> +    }
> +    return ret;
> +}
> +
> +static const TypeInfo iommufd_backend_info = {
> +    .name = TYPE_IOMMUFD_BACKEND,
> +    .parent = TYPE_OBJECT,
> +    .instance_size = sizeof(IOMMUFDBackend),
> +    .instance_init = iommufd_backend_init,
> +    .instance_finalize = iommufd_backend_finalize,
> +    .class_size = sizeof(IOMMUFDBackendClass),
> +    .class_init = iommufd_backend_class_init,
> +    .interfaces = (InterfaceInfo[]) {
> +        { TYPE_USER_CREATABLE },
> +        { }
> +    }
> +};
> +
> +static void register_types(void)
> +{
> +    type_register_static(&iommufd_backend_info);
> +}
> +
> +type_init(register_types);
> diff --git a/backends/Kconfig b/backends/Kconfig
> index f35abc1609..2cb23f62fa 100644
> --- a/backends/Kconfig
> +++ b/backends/Kconfig
> @@ -1 +1,5 @@
>  source tpm/Kconfig
> +
> +config IOMMUFD
> +    bool
> +    depends on VFIO
I don't know the state of vDPA/iommufd integration but this extra might
be added in short term.
> diff --git a/backends/meson.build b/backends/meson.build
> index 914c7c4afb..9a5cea480d 100644
> --- a/backends/meson.build
> +++ b/backends/meson.build
> @@ -20,6 +20,7 @@ if have_vhost_user
>    system_ss.add(when: 'CONFIG_VIRTIO', if_true: files('vhost-user.c'))
>  endif
>  system_ss.add(when: 'CONFIG_VIRTIO_CRYPTO', if_true: files('cryptodev-vhost.c'))
> +system_ss.add(when: 'CONFIG_IOMMUFD', if_true: files('iommufd.c'))
>  if have_vhost_user_crypto
>    system_ss.add(when: 'CONFIG_VIRTIO_CRYPTO', if_true: files('cryptodev-vhost-user.c'))
>  endif
> diff --git a/backends/trace-events b/backends/trace-events
> index 652eb76a57..d45c6e31a6 100644
> --- a/backends/trace-events
> +++ b/backends/trace-events
> @@ -5,3 +5,13 @@ dbus_vmstate_pre_save(void)
>  dbus_vmstate_post_load(int version_id) "version_id: %d"
>  dbus_vmstate_loading(const char *id) "id: %s"
>  dbus_vmstate_saving(const char *id) "id: %s"
> +
> +# iommufd.c
> +iommufd_backend_connect(int fd, bool owned, uint32_t users, int ret) "fd=%d owned=%d users=%d (%d)"
> +iommufd_backend_disconnect(int fd, uint32_t users) "fd=%d users=%d"
> +iommu_backend_set_fd(int fd) "pre-opened /dev/iommu fd=%d"
> +iommufd_backend_map_dma(int iommufd, uint32_t ioas, uint64_t iova, uint64_t size, void *vaddr, bool readonly, int ret) " iommufd=%d ioas=%d iova=0x%"PRIx64" size=0x%"PRIx64" addr=%p readonly=%d (%d)"
> +iommufd_backend_unmap_dma_non_exist(int iommufd, uint32_t ioas, uint64_t iova, uint64_t size, int ret) " Unmap nonexistent mapping: iommufd=%d ioas=%d iova=0x%"PRIx64" size=0x%"PRIx64" (%d)"
> +iommufd_backend_unmap_dma(int iommufd, uint32_t ioas, uint64_t iova, uint64_t size, int ret) " iommufd=%d ioas=%d iova=0x%"PRIx64" size=0x%"PRIx64" (%d)"
> +iommufd_backend_alloc_ioas(int iommufd, uint32_t ioas, int ret) " iommufd=%d ioas=%d (%d)"
> +iommufd_backend_free_id(int iommufd, uint32_t id, int ret) " iommufd=%d id=%d (%d)"
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 42fd09e4de..70507c0ee6 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -5224,6 +5224,18 @@ SRST
>  
>          The ``share`` boolean option is on by default with memfd.
>  
> +    ``-object iommufd,id=id[,fd=fd]``
> +        Creates an iommufd backend which allows control of DMA mapping
> +        through the /dev/iommu device.
> +
> +        The ``id`` parameter is a unique ID which frontends (such as
> +        vfio-pci of vdpa) will use to connect with the iommufd backend.
> +
> +        The ``fd`` parameter is an optional pre-opened file descriptor
> +        resulting from /dev/iommu opening. Usually the iommufd is shared
> +        across all subsystems, bringing the benefit of centralized
> +        reference counting.
> +
>      ``-object rng-builtin,id=id``
>          Creates a random number generator backend which obtains entropy
>          from QEMU builtin functions. The ``id`` parameter is a unique ID