Re: [PATCH v6 1/2] xen/domain: unify domain ID allocation

[dmkhn@proton.me]

On Sun, May 18, 2025 at 10:52:24AM +0200, Jan Beulich wrote:
> On 16.05.2025 04:04, dmkhn@proton.me wrote:
> > From: Denis Mukhin <dmukhin@ford.com>
> >
> > Currently, hypervisor code has two different non-system domain ID allocation
> > implementations:
> >
> >   (a) Sequential IDs allocation in dom0less Arm code based on max_init_domid;
> >
> >   (b) Sequential IDs allocation in XEN_DOMCTL_createdomain; does not use
> >       max_init_domid (both Arm and x86).
> >
> > It makes sense to have a common helper code for such task across architectures
> > (Arm and x86) and between dom0less / toolstack domU allocation.
> >
> > Wrap the domain ID allocation as an arch-independent function domid_alloc() in
> > common/domain.c based on rangeset.
> >
> > Allocation algorithm:
> > - If an explicit domain ID is provided, verify its availability and
> >   use it if ID is not used;
> > - Otherwise, perform an exhaustive search starting from the end of the used
> >   domain ID range. domid_alloc() guarantees that two subsequent calls will
> >   result in different IDs allocation.
> While you properly retain original logic now, the above is not an accurate
> description thereof, imo. To search "from the end" usually is understood as
> a backwards search. Whereas what you mean is that the search starts off where
> the last one finished, wrapping around when hitting the end of the valid
> range.

I have updated the description in v7:
  https://lore.kernel.org/xen-devel/20250519192306.1364471-2-dmukhin@ford.com/

> 
> Jan
>