From 27351992bf238f669dd08655d31ad111905bf899 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Alex=20Benn=C3=A9e?= Date: Mon, 21 Mar 2022 15:30:34 +0000 Subject: [PATCH] include/hw: start documenting the vhost API MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit While trying to get my head around the nest of interactions for vhost devices I though I could start by documenting the key API functions. This patch documents the main API hooks for creating and starting a vhost device as well as how the configuration changes are handled. Signed-off-by: Alex Bennée Cc: Michael S. Tsirkin Cc: Stefan Hajnoczi Cc: Marc-André Lureau Message-Id: <20220321153037.3622127-11-alex.bennee@linaro.org> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- include/hw/virtio/vhost.h | 132 +++++++++++++++++++++++++++++++++++--- 1 file changed, 122 insertions(+), 10 deletions(-) diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h index 58a73e7b7a..b291fe4e24 100644 --- a/include/hw/virtio/vhost.h +++ b/include/hw/virtio/vhost.h @@ -61,6 +61,12 @@ typedef struct VhostDevConfigOps { } VhostDevConfigOps; struct vhost_memory; + +/** + * struct vhost_dev - common vhost_dev structure + * @vhost_ops: backend specific ops + * @config_ops: ops for config changes (see @vhost_dev_set_config_notifier) + */ struct vhost_dev { VirtIODevice *vdev; MemoryListener memory_listener; @@ -108,15 +114,129 @@ struct vhost_net { NetClientState *nc; }; +/** + * vhost_dev_init() - initialise the vhost interface + * @hdev: the common vhost_dev structure + * @opaque: opaque ptr passed to backend (vhost/vhost-user/vdpa) + * @backend_type: type of backend + * @busyloop_timeout: timeout for polling virtqueue + * @errp: error handle + * + * The initialisation of the vhost device will trigger the + * initialisation of the backend and potentially capability + * negotiation of backend interface. Configuration of the VirtIO + * itself won't happen until the interface is started. + * + * Return: 0 on success, non-zero on error while setting errp. + */ int vhost_dev_init(struct vhost_dev *hdev, void *opaque, VhostBackendType backend_type, uint32_t busyloop_timeout, Error **errp); + +/** + * vhost_dev_cleanup() - tear down and cleanup vhost interface + * @hdev: the common vhost_dev structure + */ void vhost_dev_cleanup(struct vhost_dev *hdev); -int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev); -void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev); + +/** + * vhost_dev_enable_notifiers() - enable event notifiers + * @hdev: common vhost_dev structure + * @vdev: the VirtIODevice structure + * + * Enable notifications directly to the vhost device rather than being + * triggered by QEMU itself. Notifications should be enabled before + * the vhost device is started via @vhost_dev_start. + * + * Return: 0 on success, < 0 on error. + */ int vhost_dev_enable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev); + +/** + * vhost_dev_disable_notifiers - disable event notifications + * @hdev: common vhost_dev structure + * @vdev: the VirtIODevice structure + * + * Disable direct notifications to vhost device. + */ void vhost_dev_disable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev); +/** + * vhost_dev_start() - start the vhost device + * @hdev: common vhost_dev structure + * @vdev: the VirtIODevice structure + * + * Starts the vhost device. From this point VirtIO feature negotiation + * can start and the device can start processing VirtIO transactions. + * + * Return: 0 on success, < 0 on error. + */ +int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev); + +/** + * vhost_dev_stop() - stop the vhost device + * @hdev: common vhost_dev structure + * @vdev: the VirtIODevice structure + * + * Stop the vhost device. After the device is stopped the notifiers + * can be disabled (@vhost_dev_disable_notifiers) and the device can + * be torn down (@vhost_dev_cleanup). + */ +void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev); + +/** + * DOC: vhost device configuration handling + * + * The VirtIO device configuration space is used for rarely changing + * or initialisation time parameters. The configuration can be updated + * by either the guest driver or the device itself. If the device can + * change the configuration over time the vhost handler should + * register a @VhostDevConfigOps structure with + * @vhost_dev_set_config_notifier so the guest can be notified. Some + * devices register a handler anyway and will signal an error if an + * unexpected config change happens. + */ + +/** + * vhost_dev_get_config() - fetch device configuration + * @hdev: common vhost_dev_structure + * @config: pointer to device appropriate config structure + * @config_len: size of device appropriate config structure + * + * Return: 0 on success, < 0 on error while setting errp + */ +int vhost_dev_get_config(struct vhost_dev *hdev, uint8_t *config, + uint32_t config_len, Error **errp); + +/** + * vhost_dev_set_config() - set device configuration + * @hdev: common vhost_dev_structure + * @data: pointer to data to set + * @offset: offset into configuration space + * @size: length of set + * @flags: @VhostSetConfigType flags + * + * By use of @offset/@size a subset of the configuration space can be + * written to. The @flags are used to indicate if it is a normal + * transaction or related to migration. + * + * Return: 0 on success, non-zero on error + */ +int vhost_dev_set_config(struct vhost_dev *dev, const uint8_t *data, + uint32_t offset, uint32_t size, uint32_t flags); + +/** + * vhost_dev_set_config_notifier() - register VhostDevConfigOps + * @hdev: common vhost_dev_structure + * @ops: notifier ops + * + * If the device is expected to change configuration a notifier can be + * setup to handle the case. + */ +void vhost_dev_set_config_notifier(struct vhost_dev *dev, + const VhostDevConfigOps *ops); + + /* Test and clear masked event pending status. * Should be called after unmask to avoid losing events. */ @@ -136,14 +256,6 @@ 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 *hdev, uint8_t *config, - uint32_t config_len, Error **errp); -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 - */ -void vhost_dev_set_config_notifier(struct vhost_dev *dev, - const VhostDevConfigOps *ops); void vhost_dev_reset_inflight(struct vhost_inflight *inflight); void vhost_dev_free_inflight(struct vhost_inflight *inflight); -- 2.39.5