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Add hotplug support for nvme-ns devices on the NvmeBus. This enables
NVMe namespace-level hot-add and hot-remove via device_add and
device_del with proper Asynchronous Event Notification (AEN), so the
guest kernel can react to namespace topology changes.
Mark nvme-ns devices as hotpluggable and register the NvmeBus as a
hotplug handler with proper plug and unplug callbacks:
- plug: attach namespace to all started controllers and send an
Asynchronous Event Notification (AEN) with NS_ATTR_CHANGED so
the guest kernel rescans namespaces and adds the block device
- unplug: drain in-flight I/O, detach from all controllers, send
AEN, then unrealize the device. The guest kernel rescans and
removes the block device.
The plug handler skips controllers that haven't started yet
(qs_created == false) to avoid interfering with boot-time namespace
attachment in nvme_start_ctrl().
The unplug handler drains in-flight I/O via nvme_ns_drain() before
detaching the namespace from controllers, so pending requests can
complete normally without touching freed state.
For symmetry with nvme_ns_realize() which sets subsys->namespaces[nsid],
nvme_ns_unrealize() now clears that slot too making the namespace
lifecycle complete.
Both the controller bus and subsystem bus are configured as hotplug
handlers via qbus_set_bus_hotplug_handler() since nvme-ns devices
may reparent to the subsystem bus during realize.
Example hot-swap sequence using the NVMe subsystem model:
# Boot with: -device nvme-subsys,id=subsys0
# -device nvme,id=ctrl0,subsys=subsys0
# -device nvme-ns,id=ns0,drive=drv0,bus=ctrl0,nsid=1
device_del ns0 # guest receives AEN, removes /dev/nvme0n1
drive_del drv0
drive_add 0 file=disk.qcow2,format=qcow2,id=drv0,if=none
device_add nvme-ns,id=ns0,drive=drv0,bus=ctrl0,nsid=1
# guest receives AEN, adds /dev/nvme0n1
Tested with Linux 6.1 guest (NVMe driver processes AEN and rescans
namespace list automatically).
Signed-off-by: Matthieu <matthieu@min.io>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>