[cc Peter, Nikolay and libvirt list] On 02.11.23 11:06, Vladimir Sementsov-Ogievskiy wrote:

Ping.

And some addition. We have the case, when the commit

commit 7bed89958bfbf40df9ca681cefbdca63abdde39d Author: Maxim Levitsky <mlevitsk@redhat.com> Date:   Tue Oct 6 14:38:58 2020 +0200

    device_core: use drain_call_rcu in in qmp_device_add     Soon, a device removal might only happen on RCU callback execution.     This is okay for device-del which provides a DEVICE_DELETED event,     but not for the failure case of device-add.  To avoid changing     monitor semantics, just drain all pending RCU callbacks on error.

sensibly slows down vm initialization (several calls to device_add of pc-dimm).

And looking at commit message, I see that what I do in the series is exactly a suggestion to change monitor semantics.

What do you think?

Maybe we need a boolean "async" parameter for device_add, which will turn off drain_call_rcu() call and rely on user to handle DEVICE_ON?

On 05.10.23 12:29, Vladimir Sementsov-Ogievskiy wrote:

...

Hi all!

Main thing this series does is DEVICE_ON event - a counter-part to DEVICE_DELETED. A guest-driven event that device is powered-on. Details are in patch 2. The new event is paried with corresponding command query-hotplug.

v8:   - improve naming, wording and style   - make new QMP interface experimental

Vladimir Sementsov-Ogievskiy (4):    qapi/qdev.json: unite DEVICE_* event data into single structure    qapi: add DEVICE_ON and query-hotplug infrastructure    shpc: implement DEVICE_ON event and query-hotplug    pcie: implement DEVICE_ON event and query-hotplug

  hw/core/hotplug.c               |  12 +++   hw/pci-bridge/pci_bridge_dev.c  |  14 +++   hw/pci-bridge/pcie_pci_bridge.c |   1 +   hw/pci/pcie.c                   |  83 +++++++++++++++   hw/pci/pcie_port.c              |   1 +   hw/pci/shpc.c                   |  86 +++++++++++++++   include/hw/hotplug.h            |  11 ++   include/hw/pci/pci_bridge.h     |   2 +   include/hw/pci/pcie.h           |   2 +   include/hw/pci/shpc.h           |   2 +   include/hw/qdev-core.h          |   7 ++   include/monitor/qdev.h          |   6 ++   qapi/qdev.json                  | 178 +++++++++++++++++++++++++++++---   softmmu/qdev-monitor.c          |  58 +++++++++++   14 files changed, 451 insertions(+), 12 deletions(-)

-- Best regards, Vladimir