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Tsirkin" , Stefan Hajnoczi , German Maglione , =?utf-8?q?Eugenio_P=C3=A9rez?= , Anton Kuchin Subject: [PATCH v4 6/8] vhost-user: Interface for migration state transfer Date: Wed, 4 Oct 2023 14:59:02 +0200 Message-ID: <20231004125904.110781-7-hreitz@redhat.com> In-Reply-To: <20231004125904.110781-1-hreitz@redhat.com> References: <20231004125904.110781-1-hreitz@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Received-SPF: pass client-ip=170.10.129.124; envelope-from=hreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Add the interface for transferring the back-end's state during migration as defined previously in vhost-user.rst. Reviewed-by: Stefan Hajnoczi Signed-off-by: Hanna Czenczek Reviewed-by: Stefan Hajnoczi --- include/hw/virtio/vhost-backend.h | 24 +++++ include/hw/virtio/vhost.h | 78 ++++++++++++++++ hw/virtio/vhost-user.c | 148 ++++++++++++++++++++++++++++++ hw/virtio/vhost.c | 37 ++++++++ 4 files changed, 287 insertions(+) diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h index 31a251a9f5..b6eee7e9fd 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; @@ -133,6 +145,15 @@ 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; @@ -181,6 +202,9 @@ 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.h b/include/hw/virtio/vhost.h index 14621f9e79..a0d03c9fdf 100644 --- a/include/hw/virtio/vhost.h +++ b/include/hw/virtio/vhost.h @@ -348,4 +348,82 @@ 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 7bed9ad7d5..7096b148a9 100644 --- a/hw/virtio/vhost-user.c +++ b/hw/virtio/vhost-user.c @@ -74,6 +74,8 @@ enum VhostUserProtocolFeature { /* Feature 14 reserved for VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS. */ VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS = 15, VHOST_USER_PROTOCOL_F_STATUS = 16, + /* Feature 17 reserved for VHOST_USER_PROTOCOL_F_XEN_MMAP. */ + VHOST_USER_PROTOCOL_F_DEVICE_STATE = 18, VHOST_USER_PROTOCOL_F_MAX }; @@ -121,6 +123,8 @@ typedef enum VhostUserRequest { VHOST_USER_REM_MEM_REG = 38, VHOST_USER_SET_STATUS = 39, VHOST_USER_GET_STATUS = 40, + VHOST_USER_SET_DEVICE_STATE_FD = 41, + VHOST_USER_CHECK_DEVICE_STATE = 42, VHOST_USER_MAX } VhostUserRequest; @@ -212,6 +216,12 @@ 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) @@ -226,6 +236,7 @@ typedef union { VhostUserCryptoSession session; VhostUserVringArea area; VhostUserInflight inflight; + VhostUserTransferDeviceState transfer_state; } VhostUserPayload; typedef struct VhostUserMsg { @@ -2746,6 +2757,140 @@ 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, @@ -2782,4 +2927,7 @@ 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 6003e50e83..85e199f0aa 100644 --- a/hw/virtio/vhost.c +++ b/hw/virtio/vhost.c @@ -2096,3 +2096,40 @@ 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; +}