Re: [PATCH] xen/arm: Prevent Dom0 to be loaded when using dom0less

[Jan Beulich <jbeulich@xxxxxxxx>]

On 08.03.2021 15:12, Julien Grall wrote:
> On 08/03/2021 11:56, Luca Fancellu wrote:
>> This patch prevents the dom0 to be loaded skipping its
>> building and going forward to build domUs when the dom0
>> kernel is not found and at least one domU is present.
> 
> As you are skipping dom0, the domid 0 will not be usable for another 
> domain. I can see a few issues:
>     1) The first domU created will now be considered as the hardware 
> domain (see domain_create()).
>     2)  There are still a few hardcoded use of d->domain_id == 0 in the 
> codebase (I could spot at least on in the RTDS code).
>     3) Not all the code seems to be able to cope with hardware_domain is 
> NULL (although most of it looks to be only reachable by x86)?
>     4) is_hardware_domain() will return true when passing NULL. It is 
> not clear whether one may pass NULL here.
> 
> For 2), ideally this needs to be fixed. But we may also want to reserve 
> domid 0 just for sanity.

+1 to reserving ID zero in such a case.

Jan