> On Jan 26, 2022, at 4:37 AM, Stefan Hajnoczi <[email protected]> wrote: > > On Tue, Jan 25, 2022 at 09:12:28PM +0000, Jag Raman wrote: >> >> >>> On Jan 25, 2022, at 5:44 AM, Stefan Hajnoczi <[email protected]> wrote: >>> >>> On Wed, Jan 19, 2022 at 04:41:56PM -0500, Jagannathan Raman wrote: >>>> Signed-off-by: Elena Ufimtseva <[email protected]> >>>> Signed-off-by: John G Johnson <[email protected]> >>>> Signed-off-by: Jagannathan Raman <[email protected]> >>>> --- >>>> hw/remote/machine.c | 57 +++++++++++++++++++++++++++++++++++++++++++++ >>>> 1 file changed, 57 insertions(+) >>>> >>>> diff --git a/hw/remote/machine.c b/hw/remote/machine.c >>>> index 220ff01aa9..221a8430c1 100644 >>>> --- a/hw/remote/machine.c >>>> +++ b/hw/remote/machine.c >>>> @@ -22,6 +22,60 @@ >>>> #include "hw/pci/pci_host.h" >>>> #include "hw/remote/iohub.h" >>>> >>>> +static bool remote_machine_get_bus(const char *type, BusState **bus, >>>> + Error **errp) >>>> +{ >>>> + ERRP_GUARD(); >>>> + RemoteMachineState *s = REMOTE_MACHINE(current_machine); >>>> + BusState *root_bus = NULL; >>>> + PCIBus *new_pci_bus = NULL; >>>> + >>>> + if (!bus) { >>>> + error_setg(errp, "Invalid argument"); >>>> + return false; >>>> + } >>>> + >>>> + if (strcmp(type, TYPE_PCI_BUS) && strcmp(type, TYPE_PCI_BUS)) { >>>> + return true; >>>> + } >>>> + >>>> + root_bus = qbus_find_recursive(sysbus_get_default(), NULL, >>>> TYPE_PCIE_BUS); >>>> + if (!root_bus) { >>>> + error_setg(errp, "Unable to find root PCI device"); >>>> + return false; >>>> + } >>>> + >>>> + new_pci_bus = pci_isol_bus_new(root_bus, type, errp); >>>> + if (!new_pci_bus) { >>>> + return false; >>>> + } >>>> + >>>> + *bus = BUS(new_pci_bus); >>>> + >>>> + pci_bus_irqs(new_pci_bus, remote_iohub_set_irq, remote_iohub_map_irq, >>>> + &s->iohub, REMOTE_IOHUB_NB_PIRQS); >>>> + >>>> + return true; >>>> +} >>> >>> Can the user create the same PCI bus via QMP commands? If so, then this >> >> I think there is a way we could achieve it. >> >> When I looked around, both the command line and the QMP didn’t have a direct >> way to create a bus. However, there are some indirect ways. For example, the >> TYPE_LSI53C895A device creates a SCSI bus to attach SCSI devices. Similarly, >> there are some special PCI devices like TYPE_PCI_BRIDGE which create a >> secondary PCI bus. >> >> Similarly, we could implement a PCI device that creates a PCI bus with >> isolated address spaces. > > Exactly. device_add instantiates DeviceStates, not busses, so there > needs to be a parent device like a SCSI controller, a PCI bridge, etc > that owns and creates the bus. > >>> is just a convenience that saves the extra step. Or is there some magic >>> that cannot be done via QMP device_add? >>> >>> I'm asking because there are 3 objects involved and I'd like to >>> understand the lifecycle/dependencies: >>> 1. The PCIDevice we wish to export. >>> 2. The PCIBus with isolated address spaces that contains the PCIDevice. >>> 3. The vfio-user server that exports a given PCIDevice. >>> >>> Users can already create the PCIDevice via hotplug and the vfio-user >>> server via object-add. So if there's no magic they could also create the >>> PCI bus: >>> 1. device_add ...some PCI bus stuff here...,id=isol-pci-bus0 >>> 2. device_add ...the PCIDevice...,bus=isol-pci-bus0,id=mydev >>> 3. object-add x-vfio-user-server,device=mydev >> >> We are able to do 2 & 3 already. We could introduce a PCI device that >> creates an isolated PCI bus. That would cover step 1 outlined above. > > I wonder if a new device is needed or whether it's possible to add an > isol_as=on|off (default: off) option to an existing PCI bridge/expander? > Hopefully most of the code is already there.
OK, it makes sense to add isol_as=on|off (default: off) option to an existing PCI bridge/expander. Will shortly confirm with you the device that seems interesting. -- Jag > > Stefan
