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

On 12/13/2016 02:42 PM, Eduardo Habkost wrote: > 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. Hi, Sadly there is no such restriction today as far as I know. We trust the user that he knows what he is doing :) and we let libvirt implement the restriction. I do agree we should fix that.