Re: [Qemu-devel] [PATCH v7 1/4] vhost-user: add new vhost user messages to support virtio config space

[Marc-André Lureau]

Hi

On Wed, Dec 13, 2017 at 3:29 AM, Changpeng Liu <address@hidden> wrote:
> Add VHOST_USER_GET_CONFIG/VHOST_USER_SET_CONFIG messages which can be
> used for live migration of vhost user devices, also vhost user devices
> can benefit from the messages to get/set virtio config space from/to the
> I/O target. For the purpose to support virtio config space change,
> VHOST_USER_SET_CONFIG_FD message is added as the event notifier
> in case virtio config space change in the I/O target.

Why not use a new slave message instead of adding another fd to watch for?

VHOST_USER_SLAVE_SET_CONFIG: notify the master of device configuration
space change


>
> Signed-off-by: Changpeng Liu <address@hidden>
> ---
>  docs/interop/vhost-user.txt       |  45 ++++++++++++++++
>  hw/virtio/vhost-user.c            | 107 
> ++++++++++++++++++++++++++++++++++++++
>  hw/virtio/vhost.c                 |  64 +++++++++++++++++++++++
>  include/hw/virtio/vhost-backend.h |  14 +++++
>  include/hw/virtio/vhost.h         |  16 ++++++
>  5 files changed, 246 insertions(+)
>
> diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
> index 954771d..826ba18 100644
> --- a/docs/interop/vhost-user.txt
> +++ b/docs/interop/vhost-user.txt
> @@ -116,6 +116,19 @@ Depending on the request type, payload can be:
>      - 3: IOTLB invalidate
>      - 4: IOTLB access fail
>
> + * Virtio device config space
> +   -----------------------------------
> +   | offset | size | flags | payload |
> +   -----------------------------------
> +
> +   Offset: a 32-bit offset of virtio device's configuration space
> +   Size: a 32-bit configuration space access size in bytes
> +   Flags: a 32-bit value:
> +    - 0: Vhost master messages used for writeable fields
> +    - 1: Vhost master messages used for live migration
> +   Payload: Size bytes array holding the contents of the virtio
> +       device's configuration space
> +
>  In QEMU the vhost-user message is implemented with the following struct:
>
>  typedef struct VhostUserMsg {
> @@ -129,6 +142,7 @@ typedef struct VhostUserMsg {
>          VhostUserMemory memory;
>          VhostUserLog log;
>          struct vhost_iotlb_msg iotlb;
> +        VhostUserConfig config;
>      };
>  } QEMU_PACKED VhostUserMsg;
>
> @@ -596,6 +610,37 @@ Master message types
>        and expect this message once (per VQ) during device configuration
>        (ie. before the master starts the VQ).
>
> + * VHOST_USER_GET_CONFIG

Please add an empty line (same style as other messages). Same for
other messages.

> +      Id: 24
> +      Equivalent ioctl: N/A
> +      Master payload: virtio device config space

Why is the master sending the current config space? I suppose the
content should be meaningful then. Make that explicit in the spec
please

+ missing Slave payload (make it explicit that size must match)

> +
> +      Submitted by the vhost-user master to fetch the contents of the virtio
> +      device configuration space, vhost-user slave uses zero length of 
> payload
> +      to indicate an error to vhost-user master. The vhost-user master may
> +      cache the contents to avoid repeated VHOST_USER_GET_CONFIG calls.
> +
> +* VHOST_USER_SET_CONFIG
> +      Id: 25
> +      Equivalent ioctl: N/A
> +      Master payload: virtio device config space
> +
> +      Submitted by the vhost-user master when the Guest changes the virtio
> +      device configuration space and also can be used for live migration
> +      on the destination host. The vhost-user slave must check the flags
> +      field, and slaves MUST NOT accept SET_CONFIG for read-only
> +      configuration space fields unless the live migration bit is set.

I would make reply mandatory for any newly introduced message. If not,
please add the message to the list that don't in "Communication"

> +
> +* VHOST_USER_SET_CONFIG_FD
> +      Id: 26
> +      Equivalent ioctl: N/A
> +      Master payload: N/A
> +
> +      Sets the notifier file descriptor, which is passed as ancillary data.
> +      The vhost-user slave uses the file descriptor to notify the vhost-user
> +      master of changes to the virtio configuration space. The vhost-user
> +      master can read the virtio configuration space to get the latest 
> update.

Imho there should be a slave message instead.

> +
>  Slave message types
>  -------------------
>
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 093675e..037c165 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -26,6 +26,11 @@
>  #define VHOST_MEMORY_MAX_NREGIONS    8
>  #define VHOST_USER_F_PROTOCOL_FEATURES 30
>
> +/*
> + * Maximum size of virtio device config space
> + */
> +#define VHOST_USER_MAX_CONFIG_SIZE 256
> +
>  enum VhostUserProtocolFeature {
>      VHOST_USER_PROTOCOL_F_MQ = 0,
>      VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1,
> @@ -65,6 +70,9 @@ typedef enum VhostUserRequest {
>      VHOST_USER_SET_SLAVE_REQ_FD = 21,
>      VHOST_USER_IOTLB_MSG = 22,
>      VHOST_USER_SET_VRING_ENDIAN = 23,
> +    VHOST_USER_GET_CONFIG = 24,
> +    VHOST_USER_SET_CONFIG = 25,
> +    VHOST_USER_SET_CONFIG_FD = 26,
>      VHOST_USER_MAX
>  } VhostUserRequest;
>
> @@ -92,6 +100,18 @@ typedef struct VhostUserLog {
>      uint64_t mmap_offset;
>  } VhostUserLog;
>
> +typedef struct VhostUserConfig {
> +    uint32_t offset;
> +    uint32_t size;
> +    uint32_t flags;
> +    uint8_t region[VHOST_USER_MAX_CONFIG_SIZE];
> +} VhostUserConfig;
> +
> +static VhostUserConfig c __attribute__ ((unused));
> +#define VHOST_USER_CONFIG_HDR_SIZE (sizeof(c.offset) \
> +                                   + sizeof(c.size) \
> +                                   + sizeof(c.flags))
> +
>  typedef struct VhostUserMsg {
>      VhostUserRequest request;
>
> @@ -109,6 +129,7 @@ typedef struct VhostUserMsg {
>          VhostUserMemory memory;
>          VhostUserLog log;
>          struct vhost_iotlb_msg iotlb;
> +        VhostUserConfig config;
>      } payload;
>  } QEMU_PACKED VhostUserMsg;
>
> @@ -922,6 +943,89 @@ static void vhost_user_set_iotlb_callback(struct 
> vhost_dev *dev, int enabled)
>      /* No-op as the receive channel is not dedicated to IOTLB messages. */
>  }
>
> +static int vhost_user_get_config(struct vhost_dev *dev, uint8_t *config,
> +                                 uint32_t config_len)
> +{
> +    VhostUserMsg msg = {
> +        msg.request = VHOST_USER_GET_CONFIG,
> +        msg.flags = VHOST_USER_VERSION,
> +        msg.size = VHOST_USER_CONFIG_HDR_SIZE + config_len,
> +    };
> +
> +    msg.payload.config.offset = 0;
> +    msg.payload.config.size = config_len;
> +    if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
> +        return -1;
> +    }

if config_len > VHOST_USER_MAX_CONFIG_SIZE, I think there will be a
stack overflow. Add an assert() ?

> +
> +    if (vhost_user_read(dev, &msg) < 0) {
> +        return -1;
> +    }
> +
> +    if (msg.request != VHOST_USER_GET_CONFIG) {
> +        error_report("Received unexpected msg type. Expected %d received %d",
> +                     VHOST_USER_GET_CONFIG, msg.request);
> +        return -1;
> +    }
> +
> +    if (msg.size != VHOST_USER_CONFIG_HDR_SIZE + config_len) {
> +        error_report("Received bad msg size.");
> +        return -1;
> +    }
> +
> +    memcpy(config, msg.payload.config.region, config_len);
> +
> +    return 0;
> +}
> +
> +static int vhost_user_set_config(struct vhost_dev *dev, const uint8_t *data,
> +                                 uint32_t offset, uint32_t size, uint32_t 
> flags)
> +{
> +    uint8_t *p;
> +    bool reply_supported = virtio_has_feature(dev->protocol_features,
> +                                              
> VHOST_USER_PROTOCOL_F_REPLY_ACK);
> +
> +    VhostUserMsg msg = {
> +        msg.request = VHOST_USER_SET_CONFIG,
> +        msg.flags = VHOST_USER_VERSION,
> +        msg.size = VHOST_USER_CONFIG_HDR_SIZE + size,
> +    };
> +
> +    if (reply_supported) {
> +        msg.flags |= VHOST_USER_NEED_REPLY_MASK;
> +    }
> +
> +    msg.payload.config.offset = offset,
> +    msg.payload.config.size = size,
> +    msg.payload.config.flags = flags,
> +    p = msg.payload.config.region;
> +    memcpy(p, data, size);

here again, max config size should be checked.

> +
> +    if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
> +        return -1;
> +    }
> +
> +    if (reply_supported) {
> +        return process_message_reply(dev, &msg);
> +    }
> +
> +    return 0;
> +}
> +
> +static int vhost_user_set_config_fd(struct vhost_dev *dev, int fd)
> +{
> +    VhostUserMsg msg = {
> +       .request = VHOST_USER_SET_CONFIG_FD,
> +       .flags = VHOST_USER_VERSION,
> +    };
> +
> +    if (vhost_user_write(dev, &msg, &fd, 1) < 0) {
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
>  const VhostOps user_ops = {
>          .backend_type = VHOST_BACKEND_TYPE_USER,
>          .vhost_backend_init = vhost_user_init,
> @@ -948,4 +1052,7 @@ const VhostOps user_ops = {
>          .vhost_net_set_mtu = vhost_user_net_set_mtu,
>          .vhost_set_iotlb_callback = vhost_user_set_iotlb_callback,
>          .vhost_send_device_iotlb_msg = vhost_user_send_device_iotlb_msg,
> +        .vhost_get_config = vhost_user_get_config,
> +        .vhost_set_config = vhost_user_set_config,
> +        .vhost_set_config_fd = vhost_user_set_config_fd,
>  };
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index e4290ce..aa93398 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -1358,6 +1358,9 @@ void vhost_dev_cleanup(struct vhost_dev *hdev)
>      for (i = 0; i < hdev->nvqs; ++i) {
>          vhost_virtqueue_cleanup(hdev->vqs + i);
>      }
> +    if (hdev->config_ops) {
> +        event_notifier_cleanup(&hdev->config_notifier);
> +    }
>      if (hdev->mem) {
>          /* those are only safe after successful init */
>          memory_listener_unregister(&hdev->memory_listener);
> @@ -1505,6 +1508,67 @@ void vhost_ack_features(struct vhost_dev *hdev, const 
> int *feature_bits,
>      }
>  }
>
> +int vhost_dev_get_config(struct vhost_dev *hdev, uint8_t *config,
> +                         uint32_t config_len)
> +{
> +    assert(hdev->vhost_ops);
> +
> +    if (hdev->vhost_ops->vhost_get_config) {
> +        return hdev->vhost_ops->vhost_get_config(hdev, config, config_len);
> +    }
> +
> +    return -1;
> +}
> +
> +int vhost_dev_set_config(struct vhost_dev *hdev, const uint8_t *data,
> +                         uint32_t offset, uint32_t size, uint32_t flags)
> +{
> +    assert(hdev->vhost_ops);
> +
> +    if (hdev->vhost_ops->vhost_set_config) {
> +        return hdev->vhost_ops->vhost_set_config(hdev, data, offset,
> +                                                 size, flags);
> +    }
> +
> +    return -1;
> +}
> +
> +static void vhost_dev_config_notifier_read(EventNotifier *n)
> +{
> +    struct vhost_dev *hdev = container_of(n, struct vhost_dev,
> +                                         config_notifier);
> +
> +    if (event_notifier_test_and_clear(n)) {
> +        if (hdev->config_ops) {
> +            hdev->config_ops->vhost_dev_config_notifier(hdev);
> +        }
> +    }
> +}
> +
> +int vhost_dev_set_config_notifier(struct vhost_dev *hdev,
> +                                  const VhostDevConfigOps *ops)
> +{
> +    int r, fd;
> +
> +    assert(hdev->vhost_ops);
> +
> +    r = event_notifier_init(&hdev->config_notifier, 0);
> +    if (r < 0) {
> +        return r;
> +    }
> +
> +    hdev->config_ops = ops;
> +    event_notifier_set_handler(&hdev->config_notifier,
> +                               vhost_dev_config_notifier_read);
> +
> +    if (hdev->vhost_ops->vhost_set_config_fd) {
> +        fd  = event_notifier_get_fd(&hdev->config_notifier);
> +        return hdev->vhost_ops->vhost_set_config_fd(hdev, fd);
> +    }
> +
> +    return -1;
> +}
> +
>  /* Host notifiers must be enabled at this point. */
>  int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
>  {
> diff --git a/include/hw/virtio/vhost-backend.h 
> b/include/hw/virtio/vhost-backend.h
> index a7a5f22..8996d5f 100644
> --- a/include/hw/virtio/vhost-backend.h
> +++ b/include/hw/virtio/vhost-backend.h
> @@ -20,6 +20,11 @@ typedef enum VhostBackendType {
>      VHOST_BACKEND_TYPE_MAX = 3,
>  } VhostBackendType;
>
> +typedef enum VhostSetConfigType {
> +    VHOST_SET_CONFIG_TYPE_MASTER = 0,
> +    VHOST_SET_CONFIG_TYPE_MIGRATION = 1,
> +} VhostSetConfigType;
> +
>  struct vhost_dev;
>  struct vhost_log;
>  struct vhost_memory;
> @@ -84,6 +89,12 @@ typedef void (*vhost_set_iotlb_callback_op)(struct 
> vhost_dev *dev,
>                                             int enabled);
>  typedef int (*vhost_send_device_iotlb_msg_op)(struct vhost_dev *dev,
>                                                struct vhost_iotlb_msg *imsg);
> +typedef int (*vhost_set_config_op)(struct vhost_dev *dev, const uint8_t 
> *data,
> +                                   uint32_t offset, uint32_t size,
> +                                   uint32_t flags);
> +typedef int (*vhost_get_config_op)(struct vhost_dev *dev, uint8_t *config,
> +                                   uint32_t config_len);
> +typedef int (*vhost_set_config_fd_op)(struct vhost_dev *dev, int fd);
>
>  typedef struct VhostOps {
>      VhostBackendType backend_type;
> @@ -118,6 +129,9 @@ typedef struct VhostOps {
>      vhost_vsock_set_running_op vhost_vsock_set_running;
>      vhost_set_iotlb_callback_op vhost_set_iotlb_callback;
>      vhost_send_device_iotlb_msg_op vhost_send_device_iotlb_msg;
> +    vhost_get_config_op vhost_get_config;
> +    vhost_set_config_op vhost_set_config;
> +    vhost_set_config_fd_op vhost_set_config_fd;
>  } VhostOps;
>
>  extern const VhostOps user_ops;
> diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
> index 467dc77..7f43a82 100644
> --- a/include/hw/virtio/vhost.h
> +++ b/include/hw/virtio/vhost.h
> @@ -46,6 +46,12 @@ struct vhost_iommu {
>      QLIST_ENTRY(vhost_iommu) iommu_next;
>  };
>
> +typedef struct VhostDevConfigOps {
> +    /* Vhost device config space changed callback
> +     */
> +    void (*vhost_dev_config_notifier)(struct vhost_dev *dev);
> +} VhostDevConfigOps;
> +
>  struct vhost_memory;
>  struct vhost_dev {
>      VirtIODevice *vdev;
> @@ -76,6 +82,8 @@ struct vhost_dev {
>      QLIST_ENTRY(vhost_dev) entry;
>      QLIST_HEAD(, vhost_iommu) iommu_list;
>      IOMMUNotifier n;
> +    EventNotifier config_notifier;
> +    const VhostDevConfigOps *config_ops;
>  };
>
>  int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
> @@ -106,4 +114,12 @@ int vhost_net_set_backend(struct vhost_dev *hdev,
>                            struct vhost_vring_file *file);
>
>  int vhost_device_iotlb_miss(struct vhost_dev *dev, uint64_t iova, int write);
> +int vhost_dev_get_config(struct vhost_dev *dev, uint8_t *config,
> +                         uint32_t config_len);
> +int vhost_dev_set_config(struct vhost_dev *dev, const uint8_t *data,
> +                         uint32_t offset, uint32_t size, uint32_t flags);
> +/* notifier callback in case vhost device config space changed
> + */
> +int vhost_dev_set_config_notifier(struct vhost_dev *dev,
> +                                  const VhostDevConfigOps *ops);
>  #endif
> --
> 1.9.3
>
>



-- 
Marc-André Lureau