From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 66EC5EB64DA for ; Thu, 20 Jul 2023 12:14:44 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qMSXm-0003g4-C9; Thu, 20 Jul 2023 08:14:07 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qMSXi-0003fn-2X for qemu-devel@nongnu.org; Thu, 20 Jul 2023 08:14:02 -0400 Received: from out-16.mta0.migadu.com ([91.218.175.16]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qMSXa-0000OD-Bk for qemu-devel@nongnu.org; Thu, 20 Jul 2023 08:14:01 -0400 Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1689855229; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2bakeTI+gagck4M5EUwFUmezf10gmavqKh68Ty1NQA0=; b=WBhlvziJ4KXgLnRJ4OhFDCTrpqYthD1WAPPsZbpUaUuE89bkwhipSbID9iOunIrjT9r8Hx Rm3Mti9fb3qfrALyJiEn1pjZsvqEyZg161nlMBQRDFyLyYKIMaa5gvU2IkVUHwaNqavGMA ZNeAkRIbqbPCeDpzzyksZqt1dDq97No= Date: Thu, 20 Jul 2023 20:13:42 +0800 MIME-Version: 1.0 Subject: Re: [Virtio-fs] [PATCH v2 2/4] vhost-user: Interface for migration state transfer Content-Language: en-US To: Hanna Czenczek , qemu-devel@nongnu.org, virtio-fs@redhat.com Cc: =?UTF-8?Q?Eugenio_P=c3=a9rez?= , Stefan Hajnoczi , "Michael S . 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From: Hao Xu In-Reply-To: <20230712111703.28031-3-hreitz@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT Received-SPF: pass client-ip=91.218.175.16; envelope-from=hao.xu@linux.dev; helo=out-16.mta0.migadu.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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 7/12/23 19:17, Hanna Czenczek wrote: > Add the interface for transferring the back-end's state during migration > as defined previously in vhost-user.rst. > > Signed-off-by: Hanna Czenczek > --- > include/hw/virtio/vhost-backend.h | 24 +++++ > include/hw/virtio/vhost.h | 79 ++++++++++++++++ > hw/virtio/vhost-user.c | 147 ++++++++++++++++++++++++++++++ > 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..e59d0b53f8 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_migratory_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_migratory_state_op vhost_supports_migratory_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 69bf59d630..d8877496e5 100644 > --- a/include/hw/virtio/vhost.h > +++ b/include/hw/virtio/vhost.h > @@ -346,4 +346,83 @@ int vhost_dev_set_inflight(struct vhost_dev *dev, > int vhost_dev_get_inflight(struct vhost_dev *dev, uint16_t queue_size, > struct vhost_inflight *inflight); > bool vhost_dev_has_iommu(struct vhost_dev *dev); > + > +/** > + * vhost_supports_migratory_state(): Checks whether the back-end > + * supports transferring internal 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_migratory_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 Hi Hanna, In what case/situation, the back-end will have a more efficient fd? Here my understanding of this "FD of its own" is as same type as the given fd(e.g. both pipe files), why the fd from back-end makes difference? Do I miss anything here? Regards, Hao > + * 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 53a881ec2a..8e6b5485e8 100644 > --- a/hw/virtio/vhost-user.c > +++ b/hw/virtio/vhost-user.c > @@ -76,6 +76,7 @@ enum VhostUserProtocolFeature { > VHOST_USER_PROTOCOL_F_STATUS = 16, > /* Feature 17 reserved for VHOST_USER_PROTOCOL_F_XEN_MMAP. */ > VHOST_USER_PROTOCOL_F_SUSPEND = 18, > + VHOST_USER_PROTOCOL_F_MIGRATORY_STATE = 19, > VHOST_USER_PROTOCOL_F_MAX > }; > > @@ -125,6 +126,8 @@ typedef enum VhostUserRequest { > VHOST_USER_GET_STATUS = 40, > VHOST_USER_SUSPEND = 41, > VHOST_USER_RESUME = 42, > + VHOST_USER_SET_DEVICE_STATE_FD = 43, > + VHOST_USER_CHECK_DEVICE_STATE = 44, > VHOST_USER_MAX > } VhostUserRequest; > > @@ -216,6 +219,12 @@ 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) > @@ -230,6 +239,7 @@ typedef union { > VhostUserCryptoSession session; > VhostUserVringArea area; > VhostUserInflight inflight; > + VhostUserTransferDeviceState transfer_state; > } VhostUserPayload; > > typedef struct VhostUserMsg { > @@ -2838,6 +2848,140 @@ static void vhost_user_reset_status(struct vhost_dev *dev) > } > } > > +static bool vhost_user_supports_migratory_state(struct vhost_dev *dev) > +{ > + return virtio_has_feature(dev->protocol_features, > + VHOST_USER_PROTOCOL_F_MIGRATORY_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_migratory_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_migratory_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, > @@ -2874,4 +3018,7 @@ 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_migratory_state = vhost_user_supports_migratory_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 2e28e58da7..756b6d55a8 100644 > --- a/hw/virtio/vhost.c > +++ b/hw/virtio/vhost.c > @@ -2091,3 +2091,40 @@ int vhost_net_set_backend(struct vhost_dev *hdev, > > return -ENOSYS; > } > + > +bool vhost_supports_migratory_state(struct vhost_dev *dev) > +{ > + if (dev->vhost_ops->vhost_supports_migratory_state) { > + return dev->vhost_ops->vhost_supports_migratory_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; > +}