From: Hanna Czenczek <hre...@redhat.com>
Add the interface for transferring the back-end's state during migration
as defined previously in vhost-user.rst.
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
Signed-off-by: Hanna Czenczek <hre...@redhat.com>
Message-Id: <20231016134243.68248-6-hre...@redhat.com>
Reviewed-by: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
---
include/hw/virtio/vhost-backend.h | 24 +++++
include/hw/virtio/vhost-user.h | 1 +
include/hw/virtio/vhost.h | 78 ++++++++++++++++
hw/virtio/vhost-user.c | 146 ++++++++++++++++++++++++++++++
hw/virtio/vhost.c | 37 ++++++++
5 files changed, 286 insertions(+)
diff --git a/include/hw/virtio/vhost-backend.h
b/include/hw/virtio/vhost-backend.h
index 96ccc18cd3..a86d103f82 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -26,6 +26,18 @@ typedef enum VhostSetConfigType {
VHOST_SET_CONFIG_TYPE_MIGRATION = 1,
} VhostSetConfigType;
+typedef enum VhostDeviceStateDirection {
+ /* Transfer state from back-end (device) to front-end */
+ VHOST_TRANSFER_STATE_DIRECTION_SAVE = 0,
+ /* Transfer state from front-end to back-end (device) */
+ VHOST_TRANSFER_STATE_DIRECTION_LOAD = 1,
+} VhostDeviceStateDirection;
+
+typedef enum VhostDeviceStatePhase {
+ /* The device (and all its vrings) is stopped */
+ VHOST_TRANSFER_STATE_PHASE_STOPPED = 0,
+} VhostDeviceStatePhase;
+
struct vhost_inflight;
struct vhost_dev;
struct vhost_log;
@@ -129,6 +141,15 @@ typedef int (*vhost_set_config_call_op)(struct vhost_dev
*dev,
typedef void (*vhost_reset_status_op)(struct vhost_dev *dev);
+typedef bool (*vhost_supports_device_state_op)(struct vhost_dev *dev);
+typedef int (*vhost_set_device_state_fd_op)(struct vhost_dev *dev,
+ VhostDeviceStateDirection
direction,
+ VhostDeviceStatePhase phase,
+ int fd,
+ int *reply_fd,
+ Error **errp);
+typedef int (*vhost_check_device_state_op)(struct vhost_dev *dev, Error
**errp);
+
typedef struct VhostOps {
VhostBackendType backend_type;
vhost_backend_init vhost_backend_init;
@@ -176,6 +197,9 @@ typedef struct VhostOps {
vhost_force_iommu_op vhost_force_iommu;
vhost_set_config_call_op vhost_set_config_call;
vhost_reset_status_op vhost_reset_status;
+ vhost_supports_device_state_op vhost_supports_device_state;
+ vhost_set_device_state_fd_op vhost_set_device_state_fd;
+ vhost_check_device_state_op vhost_check_device_state;
} VhostOps;
int vhost_backend_update_device_iotlb(struct vhost_dev *dev,
diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h
index 20b69d8e85..d7c09ffd34 100644
--- a/include/hw/virtio/vhost-user.h
+++ b/include/hw/virtio/vhost-user.h
@@ -31,6 +31,7 @@ enum VhostUserProtocolFeature {
VHOST_USER_PROTOCOL_F_STATUS = 16,
/* Feature 17 reserved for VHOST_USER_PROTOCOL_F_XEN_MMAP. */
VHOST_USER_PROTOCOL_F_SHARED_OBJECT = 18,
+ VHOST_USER_PROTOCOL_F_DEVICE_STATE = 19,
VHOST_USER_PROTOCOL_F_MAX
};
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index 5e8183f64a..b6ee6da6ce 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -351,4 +351,82 @@ static inline int vhost_reset_device(struct vhost_dev
*hdev)
}
#endif /* CONFIG_VHOST */
+/**
+ * vhost_supports_device_state(): Checks whether the back-end supports
+ * transferring internal device state for the purpose of migration.
+ * Support for this feature is required for vhost_set_device_state_fd()
+ * and vhost_check_device_state().
+ *
+ * @dev: The vhost device
+ *
+ * Returns true if the device supports these commands, and false if it
+ * does not.
+ */
+bool vhost_supports_device_state(struct vhost_dev *dev);
+
+/**
+ * vhost_set_device_state_fd(): Begin transfer of internal state from/to
+ * the back-end for the purpose of migration. Data is to be transferred
+ * over a pipe according to @direction and @phase. The sending end must
+ * only write to the pipe, and the receiving end must only read from it.
+ * Once the sending end is done, it closes its FD. The receiving end
+ * must take this as the end-of-transfer signal and close its FD, too.
+ *
+ * @fd is the back-end's end of the pipe: The write FD for SAVE, and the
+ * read FD for LOAD. This function transfers ownership of @fd to the
+ * back-end, i.e. closes it in the front-end.
+ *
+ * The back-end may optionally reply with an FD of its own, if this
+ * improves efficiency on its end. In this case, the returned FD is
+ * stored in *reply_fd. The back-end will discard the FD sent to it,
+ * and the front-end must use *reply_fd for transferring state to/from
+ * the back-end.
+ *
+ * @dev: The vhost device
+ * @direction: The direction in which the state is to be transferred.
+ * For outgoing migrations, this is SAVE, and data is read
+ * from the back-end and stored by the front-end in the
+ * migration stream.
+ * For incoming migrations, this is LOAD, and data is read
+ * by the front-end from the migration stream and sent to
+ * the back-end to restore the saved state.
+ * @phase: Which migration phase we are in. Currently, there is only
+ * STOPPED (device and all vrings are stopped), in the future,
+ * more phases such as PRE_COPY or POST_COPY may be added.
+ * @fd: Back-end's end of the pipe through which to transfer state; note
+ * that ownership is transferred to the back-end, so this function
+ * closes @fd in the front-end.
+ * @reply_fd: If the back-end wishes to use a different pipe for state
+ * transfer, this will contain an FD for the front-end to
+ * use. Otherwise, -1 is stored here.
+ * @errp: Potential error description
+ *
+ * Returns 0 on success, and -errno on failure.
+ */
+int vhost_set_device_state_fd(struct vhost_dev *dev,
+ VhostDeviceStateDirection direction,
+ VhostDeviceStatePhase phase,
+ int fd,
+ int *reply_fd,
+ Error **errp);
+
+/**
+ * vhost_set_device_state_fd(): After transferring state from/to the
+ * back-end via vhost_set_device_state_fd(), i.e. once the sending end
+ * has closed the pipe, inquire the back-end to report any potential
+ * errors that have occurred on its side. This allows to sense errors
+ * like:
+ * - During outgoing migration, when the source side had already started
+ * to produce its state, something went wrong and it failed to finish
+ * - During incoming migration, when the received state is somehow
+ * invalid and cannot be processed by the back-end
+ *
+ * @dev: The vhost device
+ * @errp: Potential error description
+ *
+ * Returns 0 when the back-end reports successful state transfer and
+ * processing, and -errno when an error occurred somewhere.
+ */
+int vhost_check_device_state(struct vhost_dev *dev, Error **errp);
+
#endif
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 7b42ae8aae..f214df804b 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -103,6 +103,8 @@ typedef enum VhostUserRequest {
VHOST_USER_SET_STATUS = 39,
VHOST_USER_GET_STATUS = 40,
VHOST_USER_GET_SHARED_OBJECT = 41,
+ VHOST_USER_SET_DEVICE_STATE_FD = 42,
+ VHOST_USER_CHECK_DEVICE_STATE = 43,
VHOST_USER_MAX
} VhostUserRequest;
@@ -201,6 +203,12 @@ typedef struct {
uint32_t size; /* the following payload size */
} QEMU_PACKED VhostUserHeader;
+/* Request payload of VHOST_USER_SET_DEVICE_STATE_FD */
+typedef struct VhostUserTransferDeviceState {
+ uint32_t direction;
+ uint32_t phase;
+} VhostUserTransferDeviceState;
+
typedef union {
#define VHOST_USER_VRING_IDX_MASK (0xff)
#define VHOST_USER_VRING_NOFD_MASK (0x1 << 8)
@@ -216,6 +224,7 @@ typedef union {
VhostUserVringArea area;
VhostUserInflight inflight;
VhostUserShared object;
+ VhostUserTransferDeviceState transfer_state;
} VhostUserPayload;
typedef struct VhostUserMsg {
@@ -2855,6 +2864,140 @@ static void vhost_user_reset_status(struct vhost_dev
*dev)
}
}
+static bool vhost_user_supports_device_state(struct vhost_dev *dev)
+{
+ return virtio_has_feature(dev->protocol_features,
+ VHOST_USER_PROTOCOL_F_DEVICE_STATE);
+}
+
+static int vhost_user_set_device_state_fd(struct vhost_dev *dev,
+ VhostDeviceStateDirection direction,
+ VhostDeviceStatePhase phase,
+ int fd,
+ int *reply_fd,
+ Error **errp)
+{
+ int ret;
+ struct vhost_user *vu = dev->opaque;
+ VhostUserMsg msg = {
+ .hdr = {
+ .request = VHOST_USER_SET_DEVICE_STATE_FD,
+ .flags = VHOST_USER_VERSION,
+ .size = sizeof(msg.payload.transfer_state),
+ },
+ .payload.transfer_state = {
+ .direction = direction,
+ .phase = phase,
+ },
+ };
+
+ *reply_fd = -1;
+
+ if (!vhost_user_supports_device_state(dev)) {
+ close(fd);
+ error_setg(errp, "Back-end does not support migration state transfer");
+ return -ENOTSUP;
+ }
+
+ ret = vhost_user_write(dev, &msg, &fd, 1);
+ close(fd);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret,
+ "Failed to send SET_DEVICE_STATE_FD message");
+ return ret;
+ }
+
+ ret = vhost_user_read(dev, &msg);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret,
+ "Failed to receive SET_DEVICE_STATE_FD reply");
+ return ret;
+ }
+
+ if (msg.hdr.request != VHOST_USER_SET_DEVICE_STATE_FD) {
+ error_setg(errp,
+ "Received unexpected message type, expected %d, received
%d",
+ VHOST_USER_SET_DEVICE_STATE_FD, msg.hdr.request);
+ return -EPROTO;
+ }
+
+ if (msg.hdr.size != sizeof(msg.payload.u64)) {
+ error_setg(errp,
+ "Received bad message size, expected %zu, received %"
PRIu32,
+ sizeof(msg.payload.u64), msg.hdr.size);
+ return -EPROTO;
+ }
+
+ if ((msg.payload.u64 & 0xff) != 0) {
+ error_setg(errp, "Back-end did not accept migration state transfer");
+ return -EIO;
+ }
+
+ if (!(msg.payload.u64 & VHOST_USER_VRING_NOFD_MASK)) {
+ *reply_fd = qemu_chr_fe_get_msgfd(vu->user->chr);
+ if (*reply_fd < 0) {
+ error_setg(errp,
+ "Failed to get back-end-provided transfer pipe FD");
+ *reply_fd = -1;
+ return -EIO;
+ }
+ }
+
+ return 0;
+}
+
+static int vhost_user_check_device_state(struct vhost_dev *dev, Error **errp)
+{
+ int ret;
+ VhostUserMsg msg = {
+ .hdr = {
+ .request = VHOST_USER_CHECK_DEVICE_STATE,
+ .flags = VHOST_USER_VERSION,
+ .size = 0,
+ },
+ };
+
+ if (!vhost_user_supports_device_state(dev)) {
+ error_setg(errp, "Back-end does not support migration state transfer");
+ return -ENOTSUP;
+ }
+
+ ret = vhost_user_write(dev, &msg, NULL, 0);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret,
+ "Failed to send CHECK_DEVICE_STATE message");
+ return ret;
+ }
+
+ ret = vhost_user_read(dev, &msg);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret,
+ "Failed to receive CHECK_DEVICE_STATE reply");
+ return ret;
+ }
+
+ if (msg.hdr.request != VHOST_USER_CHECK_DEVICE_STATE) {
+ error_setg(errp,
+ "Received unexpected message type, expected %d, received
%d",
+ VHOST_USER_CHECK_DEVICE_STATE, msg.hdr.request);
+ return -EPROTO;
+ }
+
+ if (msg.hdr.size != sizeof(msg.payload.u64)) {
+ error_setg(errp,
+ "Received bad message size, expected %zu, received %"
PRIu32,
+ sizeof(msg.payload.u64), msg.hdr.size);
+ return -EPROTO;
+ }
+
+ if (msg.payload.u64 != 0) {
+ error_setg(errp, "Back-end failed to process its internal state");
+ return -EIO;
+ }
+
+ return 0;
+}
+
const VhostOps user_ops = {
.backend_type = VHOST_BACKEND_TYPE_USER,
.vhost_backend_init = vhost_user_backend_init,
@@ -2890,4 +3033,7 @@ const VhostOps user_ops = {
.vhost_set_inflight_fd = vhost_user_set_inflight_fd,
.vhost_dev_start = vhost_user_dev_start,
.vhost_reset_status = vhost_user_reset_status,
+ .vhost_supports_device_state = vhost_user_supports_device_state,
+ .vhost_set_device_state_fd = vhost_user_set_device_state_fd,
+ .vhost_check_device_state = vhost_user_check_device_state,
};
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 9c9ae7109e..4db9dbfd64 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -2159,3 +2159,40 @@ int vhost_reset_device(struct vhost_dev *hdev)
return -ENOSYS;
}
+
+bool vhost_supports_device_state(struct vhost_dev *dev)
+{
+ if (dev->vhost_ops->vhost_supports_device_state) {
+ return dev->vhost_ops->vhost_supports_device_state(dev);
+ }
+
+ return false;
+}
+
+int vhost_set_device_state_fd(struct vhost_dev *dev,
+ VhostDeviceStateDirection direction,
+ VhostDeviceStatePhase phase,
+ int fd,
+ int *reply_fd,
+ Error **errp)
+{
+ if (dev->vhost_ops->vhost_set_device_state_fd) {
+ return dev->vhost_ops->vhost_set_device_state_fd(dev, direction, phase,
+ fd, reply_fd, errp);
+ }
+
+ error_setg(errp,
+ "vhost transport does not support migration state transfer");
+ return -ENOSYS;
+}
+
+int vhost_check_device_state(struct vhost_dev *dev, Error **errp)
+{
+ if (dev->vhost_ops->vhost_check_device_state) {
+ return dev->vhost_ops->vhost_check_device_state(dev, errp);
+ }
+
+ error_setg(errp,
+ "vhost transport does not support migration state transfer");
+ return -ENOSYS;
+}
--
MST
