Am 27.09.2021 um 13:39 hat Kevin Wolf geschrieben: > Am 27.09.2021 um 13:06 hat Damien Hedde geschrieben: > > On 9/24/21 11:04, Kevin Wolf wrote: > > > Directly call qdev_device_add_from_qdict() for QMP device_add instead of > > > first going through QemuOpts and converting back to QDict. > > > > > > Note that this changes the behaviour of device_add, though in ways that > > > should be considered bug fixes: > > > > > > QemuOpts ignores differences between data types, so you could > > > successfully pass a string "123" for an integer property, or a string > > > "on" for a boolean property (and vice versa). After this change, the > > > correct data type for the property must be used in the JSON input. > > > > > > qemu_opts_from_qdict() also silently ignores any options whose value is > > > a QDict, QList or QNull. > > > > > > To illustrate, the following QMP command was accepted before and is now > > > rejected for both reasons: > > > > > > { "execute": "device_add", > > > "arguments": { "driver": "scsi-cd", > > > "drive": { "completely": "invalid" }, > > > "physical_block_size": "4096" } } > > > > > > Signed-off-by: Kevin Wolf <kw...@redhat.com> > > > --- > > > softmmu/qdev-monitor.c | 18 +++++++++++------- > > > 1 file changed, 11 insertions(+), 7 deletions(-) > > > > > > diff --git a/softmmu/qdev-monitor.c b/softmmu/qdev-monitor.c > > > index c09b7430eb..8622ccade6 100644 > > > --- a/softmmu/qdev-monitor.c > > > +++ b/softmmu/qdev-monitor.c > > > @@ -812,7 +812,8 @@ void hmp_info_qdm(Monitor *mon, const QDict *qdict) > > > qdev_print_devinfos(true); > > > } > > > -void qmp_device_add(QDict *qdict, QObject **ret_data, Error **errp) > > > +static void monitor_device_add(QDict *qdict, QObject **ret_data, > > > + bool from_json, Error **errp) > > > { > > > QemuOpts *opts; > > > DeviceState *dev; > > > @@ -825,7 +826,9 @@ void qmp_device_add(QDict *qdict, QObject **ret_data, > > > Error **errp) > > > qemu_opts_del(opts); > > > return; > > > } > > > - dev = qdev_device_add(opts, errp); > > > + qemu_opts_del(opts); > > > + > > > + dev = qdev_device_add_from_qdict(qdict, from_json, errp); > > > > Hi Kevin, > > > > I'm wandering if deleting the opts (which remove it from the "device" opts > > list) is really a no-op ? > > It's not exactly a no-op. Previously, the QemuOpts would only be freed > when the device is destroying, now we delete it immediately after > creating the device. This could matter in some cases. > > The one case I was aware of is that QemuOpts used to be responsible for > checking for duplicate IDs. Obviously, it can't do this job any more > when we call qemu_opts_del() right after creating the device. This is > the reason for patch 6. > > > The opts list is, eg, traversed in hw/net/virtio-net.c in the function > > failover_find_primary_device_id() which may be called during the > > virtio_net_set_features() (a TYPE_VIRTIO_NET method). > > I do not have the knowledge to tell when this method is called. But If this > > is after we create the devices. Then the list will be empty at this point > > now. > > > > It seems, there are 2 other calling sites of > > "qemu_opts_foreach(qemu_find_opts("device"), [...]" in net/vhost-user.c and > > net/vhost-vdpa.c > > Yes, you are right. These callers probably need to be changed. Going > through the command line options rather than looking at the actual > device objects that exist doesn't feel entirely clean anyway.
So I tried to have a look at the virtio-net case, and ended up very confused. Obviously looking at command line options (even of a differrent device) from within a device is very unclean. With a non-broken, i.e. type safe, device-add (as well as with the JSON CLI option introduced by this series), we can't have a QemuOpts any more that is by definition unsafe. So this code needs a replacement. My naive idea was that we just need to look at runtime state instead. Don't search the options for a device with a matching 'failover_pair_id' (which, by the way, would fail as soon as any other device introduces a property with the same name), but search for actual PCIDevices in qdev that have pci_dev->failover_pair_id set accordingly. However, the logic in failover_add_primary() suggests that we can have a state where QemuOpts for a device exist, but the device doesn't, and then it hotplugs the device from the command line options. How would we ever get into such an inconsistent state where QemuOpts contains a device that doesn't exist? Normally devices get their QemuOpts when they are created and device_finalize() deletes the QemuOpts again. Any suggestions how to get rid of the QemuOpts abuse in the failover code? If this is a device that we previously managed to rip out without deleting its QemuOpts, can we store its dev->opts (which is a type safe QDict after this series) somewhere locally instead of looking at global state? Preferably I would even like to get rid of dev->opts because we really should look at live state rather than command line options after device creation, but I guess one step at a time. (Actually, I'm half tempted to just break it because no test cases seem to exist, so apparently nobody is really interested in it.) Kevin