Re: [PATCH 1/6] xen: add a domain unique id to each domain

[Jürgen Groß <jgross@xxxxxxxx>]

On 16.11.24 11:46, Julien Grall wrote:
> Hi,
>
> On 23/10/2024 14:10, Juergen Gross wrote:
> > Xenstore is referencing domains by their domid, but reuse of a domid
> > can lead to the situation that Xenstore can't tell whether a domain
> > with that domid has been deleted and created again without Xenstore
> > noticing the domain is a new one now.
> >
> > Add a global domain creation unique id which is updated when creating
> > a new domain, and store that value in struct domain of the new domain.
> > The global unique id is initialized with the system time and updates
> > are done via the xorshift algorithm which is used for pseudo random
> > number generation, too (see https://en.wikipedia.org/wiki/Xorshift).
> >
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> > ---
> > V1:
> > - make unique_id local to function (Jan Beulich)
> > - add lock (Julien Grall)
> > - add comment (Julien Grall)
> > ---
> >   xen/common/domain.c     | 20 ++++++++++++++++++++
> >   xen/include/xen/sched.h |  3 +++
> >   2 files changed, 23 insertions(+)
> >
> > diff --git a/xen/common/domain.c b/xen/common/domain.c
> > index 92263a4fbd..3948640fb0 100644
> > --- a/xen/common/domain.c
> > +++ b/xen/common/domain.c
> > @@ -562,6 +562,25 @@ static void _domain_destroy(struct domain *d)
> >       free_domain_struct(d);
> >   }
> > +static uint64_t get_unique_id(void)
> > +{
> > +    static uint64_t unique_id;
> > +    static DEFINE_SPINLOCK(lock);
> > +    uint64_t x = unique_id ? : NOW();
> I think unique_id needs to be read within the critical section. Otherwise, 
> get_unique_id() could return the same ID twice.
Yes, you are right.


Juergen

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