On 12/13/2016 06:00 PM, Eduardo Habkost wrote:
On Tue, Dec 13, 2016 at 04:15:18PM +0200, Marcel Apfelbaum wrote:
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@redhat.com> 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.
OK, this matches what I saw on the current code.
But I would like to understand what exactly should be the rules if we fix that. Should we report only 1 slot if pci_bus_has_pcie_upstream_port(bus)?
We should report 1 slot for a bus exposed by a PCIe Root Port or PCIe Downstream Port. Be aware that 1 slot doesn't necessarily refer to only one device, we can have a multi-function device. Thanks, Marcel
(Note that pci_bus_has_pcie_upstream_port() doesn't exist in the current code, it is added by my patch)