Re: [PATCH 1/1] softmmu: fix device deletion events with -device JSON syntax

[Laurent Vivier]

On 05/01/2022 15:55, Daniel P. Berrangé wrote:
> On Wed, Jan 05, 2022 at 03:49:12PM +0100, Laurent Vivier wrote:
> > On 05/01/2022 13:38, Daniel P. Berrangé wrote:
> > > The -device JSON syntax impl leaks a reference on the created
> > > DeviceState instance. As a result when you hot-unplug the
> > > device, the device_finalize method won't be called and thus
> > > it will fail to emit the required DEVICE_DELETED event.
> > >
> > > A 'json-cli' feature was previously added against the
> > > 'device_add' QMP command QAPI schema to indicated to mgmt
> > > apps that -device supported JSON syntax. Given the hotplug
> > > bug that feature flag is no unusable for its purpose, so
> >
> > Not sure to understand: do you mean "now unusable"?
>
> An application wants to known whether QEMU can support JSON
> syntax with -device. If they look for the 'json-cli' feature
> as a witness, they'll end up using JSON with QEMU 6.2 which
> is giving them broken hotplug. This is unusable for any
> non-trivial use cases. So we need a new witness to indicate
> whether JSON is viable with -device, that only the newly
> fixed QEMU will report.

I understand that, my problem was with your sentence:

"Given the hotplug bug that feature flag is no unusable for its purpose"

Thanks,
Laurent