Re: [PATCH v5 10/11] arm/libxl: Emulated PCI device tree node in libxl

[Rahul Singh <Rahul.Singh@xxxxxxx>]

Hi Ian,

> On 7 Oct 2021, at 11:53 am, Ian Jackson <iwj@xxxxxxxxxxxxxx> wrote:
> 
> Julien Grall writes ("Re: [PATCH v5 10/11] arm/libxl: Emulated PCI device 
> tree node in libxl"):
>> On 06/10/2021 19:40, Rahul Singh wrote:
>>> diff --git a/tools/libs/light/libxl_types.idl 
>>> b/tools/libs/light/libxl_types.idl
>>> index 3f9fff653a..78b1ddf0b8 100644
>>> --- a/tools/libs/light/libxl_types.idl
>>> +++ b/tools/libs/light/libxl_types.idl
>>> @@ -644,6 +644,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
>>> 
>>>      ("arch_arm", Struct(None, [("gic_version", libxl_gic_version),
>>>                                 ("vuart", libxl_vuart_type),
>>> +                               ("vpci", libxl_defbool),
>> 
>> I have posted some comments regarding the field in v4. To summarize, 
>> AFAICT, this option is meant to be only set by libxl but you still let 
>> the toolstack (e.g. xl, libvirt) to set it.
>> 
>> If you still want to expose to the toolstack, then I think the option 
>> should be outside of arch_arm. Otherwise, this should be moved in an 
>> internal structure (Ian, do you have any suggestion?).
> 
> If it should be in an internal structure, probably the libxl create
> context.

As Stefano suggested in another email that we can remove the vpci option, if we 
reach to conclusion that we need vpci option I will move it to internal 
structure.
 
>  
> But I'm not convinced yet.  In particular, if enabling VPCI is
> necessary on ARM for hotplugged PCI devices[1], then there has to be
> a way for the admin to say "while this domain may not have any PCI
> devices right now, I may wish to hotplug some".  That's what the
> "passthrough=" option is for.

Yes I agree with you VPCI is necessary for hot plugged PCI device and once we 
implement the hotplug in future we will use the passthrough= option to enable 
VPCI.

Regards,
Rahul  

> 
> See my other mail.
> 
> [1] I think this is all true even if PCI hotplug for ARM is not
> currently implemented.
> 
> Ian.