>>> On 14.12.18 at 11:03, <roger....@citrix.com> wrote: > I expect the interdomain locking as a result of using a paging caller > domain is going to be restricted to the p2m lock of the caller domain, > as a result of the usage of copy to/from helpers. > > Maybe the less intrusive change would be to just allow locking the > caller p2m lock (that only lock) regardless of the subject domain lock > level?
With caller != subject, and with the lock level then being higher than all "normal" ones, this might be an option. But from the very beginning we should keep the transitive aspect here in mind: If Dom0 controls a PVH domain which controls a HVM one, the Dom0 p2m lock may also need allowing to nest inside the PVH DomU's one, so it'll be a total of two extra new lock levels even if we restrict this to the p2m locks. Furthermore, if we limited this to the p2m locks, it would become illegal to obtain any of the higher lock level locks (i.e. ones that nest inside the p2m lock) for the caller domain. I'm not sure that's a good idea. As mentioned before, if caller locks collectively all get obtained inside any subject domain ones, applying a bias to all lock levels would perhaps be preferable. The question is whether this criteria holds. I also as of yet can't see how this could be expressed transparently to existing code. Yet obviously having to change various p2m_lock() invocations would be rather undesirable. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
