> On Jan 26, 2022, at 4:37 AM, Stefan Hajnoczi <stefa...@redhat.com> wrote:
>
> On Tue, Jan 25, 2022 at 09:12:28PM +0000, Jag Raman wrote:
>>
>>
>>> On Jan 25, 2022, at 5:44 AM, Stefan Hajnoczi <stefa...@redhat.com> wrote:
>>>
>>> On Wed, Jan 19, 2022 at 04:41:56PM -0500, Jagannathan Raman wrote:
>>>> Signed-off-by: Elena Ufimtseva <elena.ufimts...@oracle.com>
>>>> Signed-off-by: John G Johnson <john.g.john...@oracle.com>
>>>> Signed-off-by: Jagannathan Raman <jag.ra...@oracle.com>
>>>> ---
>>>> 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
