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Re: [PATCH v4] xen/domain: introduce DOMID_ANY
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 4 Feb 2026 10:15:30 +0100
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- Cc: dmukhin@xxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, andrew.cooper3@xxxxxxxxxx, anthony.perard@xxxxxxxxxx, julien@xxxxxxx, michal.orzel@xxxxxxx, sstabellini@xxxxxxxxxx, dmukhin@xxxxxxxx
- Delivery-date: Wed, 04 Feb 2026 09:15:49 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 04.02.2026 10:00, Roger Pau Monné wrote:
> On Wed, Feb 04, 2026 at 08:56:10AM +0100, Jan Beulich wrote:
>> On 04.02.2026 08:49, Roger Pau Monné wrote:
>>> Also, I would remove the tools guards, I think once a DOMID_ constant
>>> is allocated it becomes part of the public ABI, and it cannot be
>>> withdrawn. See for example DOMID_IDLE: it's only used internally in
>>> the hypervisor AFAICT, yet the define is fully visible in the
>>> headers.
>>
>> It was me to ask for it to be guarded like this. DOMID_IDLE (and perhaps
>> others) not being guarded (at least for IDLE: by just __XEN__) imo was a
>> mistake. That mistake may in fact be correctable, if we could prove that
>> the ID cannot usefully be passed into anywhere.
>
> Even if it's not passed into anything, does it make sense to guard
> them? The reserved domid values are already consumed, ie: cannot be
> reused in any way. It just seem to me like more ifdefery churn for no
> specific benefit.
Well. From an abstract perspective, purely hypothetical at this point, I
could see a potential need to re-number them, e.g. to simplify checking
against groups of these special IDs.
Yes, excess #ifdef-ary is an issue. Excess exposure of things also is,
though. Finding the right balance between both can be interesting.
Jan
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