Re: [Xen-devel] [PATCH v3 4/6] libxl: allow creation of domains with a specified or random domid

[Ian Jackson <ian.jackson@xxxxxxxxxx>]

Durrant, Paul writes ("RE: [PATCH v3 4/6] libxl: allow creation of domains with 
a specified or random domid"):
> [Ian:]
> > I think there are only two possible solutions:
> > 
> >   - Check the domain's entry in the recent list *after* creating
> >     the domain in Xen.  This involves accepting that we will
> >     reuse the domid but only for a domain we are in the early
> >     stages of constructing, so hopefully without bad consequence?
> > 
> >   - Take the recent domid lock.
> > 
> 
> Or take a global file lock in libxl around domain creation and destruction?

We want domain construction to be concurrent, when it can be.  So I
think a lock around just xc_domain_create is OK but a lock around the
whole operation is not.

> > Also, it seems to me that we should check the recent domid list if we
> > let Xen choose the domid.  Maybe that can be in a subsequent patch...
> 
> Well, we could solve all this, remove the need for a file and all the 
> associated complexity by simply keeping history inside the hypervisor. I 
> don't know how the Xen maintainers will feel about that though, as Xen itself 
> shouldn't have a problem with eager domid re-use.

I think this doesn't need to be done in the hypervisor so I am
inclined to say it shouldn't be.  Also, there is a lot of policy here...

Ian.

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