Re: [libvirt] [Qemu-devel] [RFC] qmp: query-device-slots command

On Tue, Dec 13, 2016 at 12:04:17PM +0100, Markus Armbruster wrote: > Quick interface review only: > > Eduardo Habkost <ehabkost(a)redhat.com&gt; writes: > >> This adds a new command to QMP: query-device-slots. It will allow >> management software to query possible slots where devices can be >> plugged. >> >> This implementation of the command will return: >> >> * Multiple PCI slots per bus, in the case of PCI buses; >> * One slot per bus in the case of the other buses; > > Umm, that doesn't seem right. For instance, a SCSI bus has multiple > slots. The slot address is the SCSI ID. An IDE bus may have one (SATA) > or two (PATA). For more examples, see qdev-device-use.txt section > "Specifying Bus and Address on Bus". Yes, I should have clarified that: this version changes only PCI to expose multiple slots, but other buses also need be changed to implement BusClass::enumerate_slots() properly, too. > >> * One slot for each entry from query-hotpluggable-cpus. >> In the example below, I am not sure if the PCIe ports are all >> supposed to report all slots, but I didn't find any existing >> field in PCIBus that would help me figure out the actual number >> of slots in a given PCI bus. >> >> Git tree >> -------- >> >> This patch needs the previous query-machines series I am working >> on. The full tree can be found on the git tree at: >> >> git://github.com/ehabkost/qemu-hacks.git work/query-machines-bus-info >> >> Example output >> -------------- >> >> The following output was returned by QEMU when running it as: >> >> $ qemu-system-x86_64 -machine q35 \ >> -readconfig docs/q35-chipset.cfg \ >> -smp 4,maxcpus=8,sockets=2,cores=2,threads=2 >> >> { >> "return": [ > > Are you sure >3000 lines of example output make sense here? I'm not. :) That's why I need feedback from the PCI experts. I believe most of the PCI ports on q35 accept only one device, but I see no code implementing that restriction, and no obvious PCIBus or PCIBusClass field indicating that.

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