Re: [PATCH v7 03/21] multi-process: setup PCI host bridge for remote device

[Jag Raman]

> On Jun 30, 2020, at 11:17 AM, Stefan Hajnoczi <stefanha@redhat.com> wrote:
> 
> On Sat, Jun 27, 2020 at 10:09:25AM -0700, elena.ufimtseva@oracle.com wrote:
>> diff --git a/hw/pci-host/remote.c b/hw/pci-host/remote.c
>> new file mode 100644
>> index 0000000000..5ea9af4154
>> --- /dev/null
>> +++ b/hw/pci-host/remote.c
>> @@ -0,0 +1,63 @@
>> +/*
>> + * Remote PCI host device
>> + *
>> + * Copyright © 2018, 2020 Oracle and/or its affiliates.
>> + *
>> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
>> + * See the COPYING file in the top-level directory.
>> + *
> 
> A little more detail would be nice:
> 
>  Unlike PCI host devices that model physical hardware, the purpose of
>  this PCI host is to host multi-process QEMU remote PCI devices.
> 
>  Multi-process QEMU talks to a remote PCI device that runs in a
>  separate process. In order to reuse QEMU device models in the remote
>  process we need a PCI bus that holds the devices.
> 
>  This PCI host is purely a container for PCI devices. It's fake in the
>  sense that the guest never sees this PCI host and has no way of
>  accessing it. It's job is just to provide the environment that QEMU
>  PCI device models need when running in a remote process.
> 
> I think this could be restated more clearly but hopefully it
> communicates the purpose of hw/pci-host/remote.c. :P

OK, we get the theme of the message. :)

> 
>> +typedef struct RemotePCIHost {
>> +    /*< private >*/
>> +    PCIExpressHost parent_obj;
>> +    /*< public >*/
>> +
>> +    MemoryRegion *mr_pci_mem;
>> +    MemoryRegion *mr_sys_mem;
> 
> Unused? Please add mr_sys_mem if and when it is used.

Got it. We will add it in the later patches that use these.

--
Jag