On 01.11.2024 07:48, Jürgen Groß wrote: > On 31.10.24 11:59, Jan Beulich wrote: >> On 23.10.2024 15:10, Juergen Gross wrote: >>> Add a bitmap with one bit per possible domid indicating the respective >>> domain has changed its state (created, deleted, dying, crashed, >>> shutdown). >>> >>> Registering the VIRQ_DOM_EXC event will result in setting the bits for >>> all existing domains and resetting all other bits. >> >> That's furthering the "there can be only one consumer" model that also >> is used for VIRQ_DOM_EXC itself. I consider the existing model flawed >> (nothing keeps a 2nd party with sufficient privilege from invoking >> XEN_DOMCTL_set_virq_handler a 2nd time, taking away the notification >> from whoever had first requested it), and hence I dislike this being >> extended. Conceivably multiple parties may indeed be interested in >> this kind of information. At which point resetting state when the vIRQ >> is bound is questionable (or the data would need to become per-domain >> rather than global, or even yet more fine-grained, albeit >> ->virq_to_evtchn[] is also per-domain, when considering global vIRQ-s). > > The bitmap is directly tied to the VIRQ_DOM_EXC anyway, as it is that > event which makes the consumer look into the bitmap via the new hypercall. > > If we decide to allow multiple consumers of VIRQ_DOM_EXC, we'll need to > have one bitmap per consumer of the event. This is not very hard to > modify. > > If you'd like that better, I can dynamically allocate the bitmap on > binding VIRQ_DOM_EXC and freeing it again when unbinding is done.
I'd prefer that indeed, yet I'm also curious what other maintainers think. Jan
