On 26 September 2017 at 18:27, Thomas Huth <th...@redhat.com> wrote: > On 25.09.2017 19:59, Eduardo Habkost wrote: >> On Mon, Sep 25, 2017 at 07:42:13PM +0200, Thomas Huth wrote: >> "make check" found a few candidates: >> https://travis-ci.org/ehabkost/qemu/jobs/278743999 >> >> Initialization of device dpcd failed: Device 'dpcd' does not support >> hotplugging >> [...] >> Initialization of device nand failed: Device 'nand' does not support >> hotplugging > > I've now had a look at those, and I now feel like the whole > "hotpluggable = false by default" idea was either just wrong or there > are other smart ideas necessary to solve this issue: These devices are > created during the instance_init() function of another device, e.g. > "dpcd" is created in the xlnx_dp_init() function, which is the > instance_init of TYPE_XLNX_DP. Now, instance_init() can be called at any > time during runtime, even without really adding the device, e.g. for > parameter introspection (try "device_add xlnx.v-dp,help" at the HMP > prompt for example).
This is a bit weird though, because it means we have a lot of devices which are "it's OK to instance_init this but not to actually create (realize) it". I don't think that that should count as hotpluggable. (Is it actually useful to be able to call "help" for a device that it is not possible to create?) > But just setting "hotpluggable = true" for a device (e.g. "dpcd") which > could be created during instance_init also does not sound very > attractive to me... Not sure about any good alternative way to tackle > this right now, maybe I've eventually got to check user_creatable in > device_set_realized, too, or move the hotpluggable checks to > qmp_device_add() instead... I'll think about that for a while... > suggestions welcome! I think the general principle of defaulting to "you need to specifically mark the device if you want it to be permitted to hotplug it" seems right -- even devices which are created under the hood by the real hotpluggable device still need to be written to support it (ie by having a finalize method or whatever to clean up). So they should probably be marked as "hotpluggable but not user createable" or similar. We just need to get the details right. thanks -- PMM
