Re: [PATCH v14 1/4] xen/domain: unify domain ID allocation

[dmkhn@xxxxxxxxx]

On Fri, Aug 08, 2025 at 06:42:03PM +0100, Julien Grall wrote:
> Hi Denis,
> 
> On 08/08/2025 03:19, dmkhn@xxxxxxxxx wrote:
> > From: Denis Mukhin <dmukhin@xxxxxxxx>
> >
> > Currently, there are two different domain ID allocation implementations:
> >
> >    1) Sequential IDs allocation in dom0less Arm code based on 
> > max_init_domid;
> >
> >    2) Sequential IDs allocation in XEN_DOMCTL_createdomain; does not use
> >       max_init_domid (both Arm and x86).
> >
> > The domain ID allocation covers dom0 or late hwdom, predefined domains,
> > post-boot domains, excluding Xen system domains (domid >=
> > DOMID_FIRST_RESERVED).
> >
> > It makes sense to have a common helper code for such task across 
> > architectures
> > (Arm and x86) and between dom0less / toolstack domU allocation.
> >
> > Note, fixing dependency on max_init_domid is out of scope of this patch.
> >
> > Wrap the domain ID allocation as an arch-independent function domid_alloc() 
> > in
> > new common/domid.c based on the bitmap.
> >
> > Allocation algorithm:
> > - If an explicit domain ID is provided, verify its availability and use it 
> > if
> >    ID is not used;
> > - If DOMID_INVALID is provided, search the range 
> > [1..DOMID_FIRST_RESERVED-1],
> >    starting from the last used ID.
> >    Implementation guarantees that two consecutive calls will never return 
> > the
> >    same ID. ID#0 is reserved for the first boot domain (currently, dom0) and
> >    excluded from the allocation range.
> >
> > Remove is_free_domid() helper as it is not needed now.
> >
> > No functional change intended.
> >
> > Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
> 
> Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>

Thank you!

> 
> Cheers,
> 
> --
> Julien Grall
> 
>