Vladimir Sementsov-Ogievskiy <vsement...@yandex-team.ru> writes:
> Add command to sync config from vhost-user backend to the device. It
> may be helpful when VHOST_USER_SLAVE_CONFIG_CHANGE_MSG failed or not
> triggered interrupt to the guest or just not available (not supported
> by vhost-user server).
>
> Command result is racy if allow it during migration. Let's allow the
> sync only in RUNNING state.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@yandex-team.ru>
> ---
> hw/block/vhost-user-blk.c | 1 +
> hw/virtio/virtio-pci.c | 9 ++++++++
> include/hw/qdev-core.h | 3 +++
> qapi/qdev.json | 23 +++++++++++++++++++
> system/qdev-monitor.c | 48 +++++++++++++++++++++++++++++++++++++++
> 5 files changed, 84 insertions(+)
>
> diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
> index 091d2c6acf..2f301f380c 100644
> --- a/hw/block/vhost-user-blk.c
> +++ b/hw/block/vhost-user-blk.c
> @@ -588,6 +588,7 @@ static void vhost_user_blk_class_init(ObjectClass *klass,
> void *data)
>
> device_class_set_props(dc, vhost_user_blk_properties);
> dc->vmsd = &vmstate_vhost_user_blk;
> + dc->sync_config = vhost_user_blk_sync_config;
> set_bit(DEVICE_CATEGORY_STORAGE, dc->categories);
> vdc->realize = vhost_user_blk_device_realize;
> vdc->unrealize = vhost_user_blk_device_unrealize;
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index b1d02f4b3d..0d91e8b5dc 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -2351,6 +2351,14 @@ static void virtio_pci_dc_realize(DeviceState *qdev,
> Error **errp)
> vpciklass->parent_dc_realize(qdev, errp);
> }
>
> +static int virtio_pci_sync_config(DeviceState *dev, Error **errp)
> +{
> + VirtIOPCIProxy *proxy = VIRTIO_PCI(dev);
> + VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> +
> + return qdev_sync_config(DEVICE(vdev), errp);
> +}
> +
> static void virtio_pci_class_init(ObjectClass *klass, void *data)
> {
> DeviceClass *dc = DEVICE_CLASS(klass);
> @@ -2367,6 +2375,7 @@ static void virtio_pci_class_init(ObjectClass *klass,
> void *data)
> device_class_set_parent_realize(dc, virtio_pci_dc_realize,
> &vpciklass->parent_dc_realize);
> rc->phases.hold = virtio_pci_bus_reset_hold;
> + dc->sync_config = virtio_pci_sync_config;
> }
>
> static const TypeInfo virtio_pci_info = {
> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
> index 9228e96c87..87135bdcdf 100644
> --- a/include/hw/qdev-core.h
> +++ b/include/hw/qdev-core.h
> @@ -95,6 +95,7 @@ typedef void (*DeviceUnrealize)(DeviceState *dev);
> typedef void (*DeviceReset)(DeviceState *dev);
> typedef void (*BusRealize)(BusState *bus, Error **errp);
> typedef void (*BusUnrealize)(BusState *bus);
> +typedef int (*DeviceSyncConfig)(DeviceState *dev, Error **errp);
>
> /**
> * struct DeviceClass - The base class for all devices.
> @@ -162,6 +163,7 @@ struct DeviceClass {
> DeviceReset reset;
> DeviceRealize realize;
> DeviceUnrealize unrealize;
> + DeviceSyncConfig sync_config;
>
> /**
> * @vmsd: device state serialisation description for
> @@ -546,6 +548,7 @@ bool qdev_hotplug_allowed(DeviceState *dev, Error **errp);
> */
> HotplugHandler *qdev_get_hotplug_handler(DeviceState *dev);
> void qdev_unplug(DeviceState *dev, Error **errp);
> +int qdev_sync_config(DeviceState *dev, Error **errp);
> void qdev_simple_device_unplug_cb(HotplugHandler *hotplug_dev,
> DeviceState *dev, Error **errp);
> void qdev_machine_creation_done(void);
> diff --git a/qapi/qdev.json b/qapi/qdev.json
> index facaa0bc6a..fc5e125a45 100644
> --- a/qapi/qdev.json
> +++ b/qapi/qdev.json
> @@ -161,3 +161,26 @@
> ##
> { 'event': 'DEVICE_UNPLUG_GUEST_ERROR',
> 'data': { '*device': 'str', 'path': 'str' } }
> +
> +##
> +# @device-sync-config:
> +#
> +# Synchronize device configuration from host to guest part. First,
> +# copy the configuration from the host part (backend) to the guest
> +# part (frontend). Then notify guest software that device
> +# configuration changed.
Blank line here, please.
> +# The command may be used to notify the guest about block device
> +# capcity change. Currently only vhost-user-blk device supports
> +# this.
> +#
> +# @id: the device's ID or QOM path
> +#
> +# Features:
> +#
> +# @unstable: The command is experimental.
> +#
> +# Since: 9.1
> +##
> +{ 'command': 'device-sync-config',
> + 'features': [ 'unstable' ],
> + 'data': {'id': 'str'} }
> diff --git a/system/qdev-monitor.c b/system/qdev-monitor.c
> index 264978aa40..47bfc0506e 100644
> --- a/system/qdev-monitor.c
> +++ b/system/qdev-monitor.c
> @@ -23,6 +23,7 @@
> #include "monitor/monitor.h"
> #include "monitor/qdev.h"
> #include "sysemu/arch_init.h"
> +#include "sysemu/runstate.h"
> #include "qapi/error.h"
> #include "qapi/qapi-commands-qdev.h"
> #include "qapi/qmp/dispatch.h"
> @@ -971,6 +972,53 @@ void qmp_device_del(const char *id, Error **errp)
> }
> }
>
> +int qdev_sync_config(DeviceState *dev, Error **errp)
> +{
> + DeviceClass *dc = DEVICE_GET_CLASS(dev);
> +
> + if (!dc->sync_config) {
> + error_setg(errp, "device-sync-config is not supported for '%s'",
> + object_get_typename(OBJECT(dev)));
> + return -ENOTSUP;
> + }
> +
> + return dc->sync_config(dev, errp);
> +}
> +
> +void qmp_device_sync_config(const char *id, Error **errp)
> +{
> + DeviceState *dev;
> +
> + /*
> + * During migration there is a race between syncing`configuration and
> + * migrating it (if migrate first, that target would get outdated
> version),
> + * so let's just not allow it.
Wrap comment lines around column 70 for legibility, please.
> + *
> + * Moreover, let's not rely on setting up interrupts in paused
> + * state, which may be a part of migration process.
We discussed this in review of v3. You wanted to check whether the
problem is real. Is it?
> + */
> +
> + if (migration_is_running()) {
> + error_setg(errp, "Config synchronization is not allowed "
> + "during migration");
> + return;
> + }
> +
> + if (!runstate_is_running()) {
> + error_setg(errp, "Config synchronization allowed only in '%s' state,
> "
Suggest a line break after errp,
> + "current state is '%s'", RunState_str(RUN_STATE_RUNNING),
> + RunState_str(runstate_get()));
> + return;
> + }
> +
> + dev = find_device_state(id, true, errp);
> + if (!dev) {
> + return;
> + }
> +
> + qdev_sync_config(dev, errp);
> +}
> +
> void hmp_device_add(Monitor *mon, const QDict *qdict)
> {
> Error *err = NULL;
