Re: [Xen-devel] [PATCH 06/12 v3] xen/arm: vpl011: Add a new vuart node in the xenstore

[Bhupinder Thakur <bhupinder.thakur@xxxxxxxxxx>]

Hi Wei,


> [...]
>> >> @@ -151,13 +154,19 @@ retry_transaction:
>> >>      if (rc) goto out;
>> >>
>> >>      if (!libxl_only) {
>> >> -        rc = libxl__xs_write_checked(gc, t, 
>> >> GCSPRINTF("%s/frontend",libxl_path),
>> >> -                                     frontend_path);
>> >> -        if (rc) goto out;
>> >> +        if (fents || ro_fents)
>> >> +        {
>> >> +            rc = libxl__xs_write_checked(gc, t, 
>> >> GCSPRINTF("%s/frontend",libxl_path),
>> >> +                                         frontend_path);
>> >> +            if (rc) goto out;
>> >> +        }
>> >>
>> >> -        rc = libxl__xs_write_checked(gc, t, 
>> >> GCSPRINTF("%s/backend",libxl_path),
>> >> -                                     backend_path);
>> >> -        if (rc) goto out;
>> >> +        if (bents)
>> >> +        {
>> >> +            rc = libxl__xs_write_checked(gc, t, 
>> >> GCSPRINTF("%s/backend",libxl_path),
>> >> +                                         backend_path);
>> >> +            if (rc) goto out;
>> >> +        }
>> >
>> > What is this for?
>> >
>> > If there is no fe or be entries you skip the path creation altogether.
>> > But why? This doesn't seem to be related to your patch.
>> For vuart, I am adding only a front end node but the
>> libxl__device_generic_add() creates the backend path also,even though
>> there is no backend node. To remove that hanging be path, I added this
>> check.
>> >
>> > At least explain this a bit in the commit message?
>> I will add more details in the commit message.
>>
>
> Preferable it should be in a separate patch. That would make review
> easier.
>
> But there is another question: how do you know if Dom0 is servicing a
> DomU? How do you construct a libxl__device struct should you want to
> manipulate vuart?
>
Can you please elaborate more on this question? I am adding the vuart
console node at the same place where the PV console node is added. I
believe, the check that I have added should be a generic check valid
for any device creation.

Regards,
Bhupinder

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