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include/hw: start documenting the vhost API
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 <alex.bennee@linaro.org> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Stefan Hajnoczi <stefanha@redhat.com> Cc: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <20220321153037.3622127-11-alex.bennee@linaro.org> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Alex Bennée
Michael S. Tsirkin
parent
bcf317f859
commit
27351992bf
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@ -61,6 +61,12 @@ typedef struct VhostDevConfigOps {
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} VhostDevConfigOps;
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struct vhost_memory;
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/**
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* struct vhost_dev - common vhost_dev structure
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* @vhost_ops: backend specific ops
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* @config_ops: ops for config changes (see @vhost_dev_set_config_notifier)
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*/
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struct vhost_dev {
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VirtIODevice *vdev;
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MemoryListener memory_listener;
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@ -108,15 +114,129 @@ struct vhost_net {
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NetClientState *nc;
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};
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/**
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* vhost_dev_init() - initialise the vhost interface
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* @hdev: the common vhost_dev structure
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* @opaque: opaque ptr passed to backend (vhost/vhost-user/vdpa)
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* @backend_type: type of backend
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* @busyloop_timeout: timeout for polling virtqueue
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* @errp: error handle
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*
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* The initialisation of the vhost device will trigger the
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* initialisation of the backend and potentially capability
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* negotiation of backend interface. Configuration of the VirtIO
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* itself won't happen until the interface is started.
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*
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* Return: 0 on success, non-zero on error while setting errp.
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*/
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int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
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VhostBackendType backend_type,
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uint32_t busyloop_timeout, Error **errp);
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/**
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* vhost_dev_cleanup() - tear down and cleanup vhost interface
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* @hdev: the common vhost_dev structure
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*/
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void vhost_dev_cleanup(struct vhost_dev *hdev);
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int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev);
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void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev);
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/**
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* vhost_dev_enable_notifiers() - enable event notifiers
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* @hdev: common vhost_dev structure
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* @vdev: the VirtIODevice structure
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*
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* Enable notifications directly to the vhost device rather than being
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* triggered by QEMU itself. Notifications should be enabled before
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* the vhost device is started via @vhost_dev_start.
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*
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* Return: 0 on success, < 0 on error.
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*/
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int vhost_dev_enable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev);
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/**
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* vhost_dev_disable_notifiers - disable event notifications
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* @hdev: common vhost_dev structure
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* @vdev: the VirtIODevice structure
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*
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* Disable direct notifications to vhost device.
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*/
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void vhost_dev_disable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev);
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/**
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* vhost_dev_start() - start the vhost device
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* @hdev: common vhost_dev structure
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* @vdev: the VirtIODevice structure
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*
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* Starts the vhost device. From this point VirtIO feature negotiation
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* can start and the device can start processing VirtIO transactions.
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*
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* Return: 0 on success, < 0 on error.
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*/
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int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev);
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/**
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* vhost_dev_stop() - stop the vhost device
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* @hdev: common vhost_dev structure
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* @vdev: the VirtIODevice structure
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*
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* Stop the vhost device. After the device is stopped the notifiers
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* can be disabled (@vhost_dev_disable_notifiers) and the device can
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* be torn down (@vhost_dev_cleanup).
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*/
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void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev);
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/**
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* DOC: vhost device configuration handling
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*
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* The VirtIO device configuration space is used for rarely changing
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* or initialisation time parameters. The configuration can be updated
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* by either the guest driver or the device itself. If the device can
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* change the configuration over time the vhost handler should
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* register a @VhostDevConfigOps structure with
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* @vhost_dev_set_config_notifier so the guest can be notified. Some
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* devices register a handler anyway and will signal an error if an
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* unexpected config change happens.
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*/
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/**
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* vhost_dev_get_config() - fetch device configuration
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* @hdev: common vhost_dev_structure
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* @config: pointer to device appropriate config structure
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* @config_len: size of device appropriate config structure
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*
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* Return: 0 on success, < 0 on error while setting errp
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*/
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int vhost_dev_get_config(struct vhost_dev *hdev, uint8_t *config,
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uint32_t config_len, Error **errp);
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/**
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* vhost_dev_set_config() - set device configuration
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* @hdev: common vhost_dev_structure
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* @data: pointer to data to set
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* @offset: offset into configuration space
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* @size: length of set
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* @flags: @VhostSetConfigType flags
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*
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* By use of @offset/@size a subset of the configuration space can be
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* written to. The @flags are used to indicate if it is a normal
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* transaction or related to migration.
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*
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* Return: 0 on success, non-zero on error
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*/
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int vhost_dev_set_config(struct vhost_dev *dev, const uint8_t *data,
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uint32_t offset, uint32_t size, uint32_t flags);
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/**
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* vhost_dev_set_config_notifier() - register VhostDevConfigOps
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* @hdev: common vhost_dev_structure
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* @ops: notifier ops
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*
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* If the device is expected to change configuration a notifier can be
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* setup to handle the case.
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*/
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void vhost_dev_set_config_notifier(struct vhost_dev *dev,
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const VhostDevConfigOps *ops);
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/* Test and clear masked event pending status.
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* Should be called after unmask to avoid losing events.
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*/
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@ -136,14 +256,6 @@ int vhost_net_set_backend(struct vhost_dev *hdev,
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struct vhost_vring_file *file);
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int vhost_device_iotlb_miss(struct vhost_dev *dev, uint64_t iova, int write);
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int vhost_dev_get_config(struct vhost_dev *hdev, uint8_t *config,
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uint32_t config_len, Error **errp);
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int vhost_dev_set_config(struct vhost_dev *dev, const uint8_t *data,
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uint32_t offset, uint32_t size, uint32_t flags);
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/* notifier callback in case vhost device config space changed
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*/
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void vhost_dev_set_config_notifier(struct vhost_dev *dev,
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const VhostDevConfigOps *ops);
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void vhost_dev_reset_inflight(struct vhost_inflight *inflight);
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void vhost_dev_free_inflight(struct vhost_inflight *inflight);
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