Re: [Draft F] Xen on ARM vITS Handling

[Ian Campbell <ian.campbell@citrix.com>]

On Tue, 2015-06-16 at 20:20 +0530, Vijay Kilari wrote:
> On Thu, Jun 11, 2015 at 3:10 PM, Ian Campbell <ian.campbell@citrix.com> wrote:
> > Draft F follows. Also at:
> > http://xenbits.xen.org/people/ianc/vits/draftF.{pdf,html}
> >
> >
> > ## Per-domain `struct pending_irq` for `vLPI`s
> >
> > Internally Xen uses a `struct pending_irq` to track the status of any
> > pending virtual IRQ, including a virtual LPI.
> >
> > Upon domain creation an array of such `struct pending_irq`'s will be
> > allocated to cover the range `8192..nr_lpis` (for the number of LPIs
> > which the guest is configured with) and a pointer this array will be
> > stored in the `struct domain`. The function `irq_to_pending` will be
> > modified to lookup interupts in the LPI range in this array.
> >.
> 
> nr_lpis can be large if more devices are assigned to domain.
> As I was suggesting on #xenarm chat, is it ok to use RB-tree instead of array?
> 
> what should be value for nr_lpis?

It should be user configurable and default to the sum of the number of
events on all devices at start of day.

I think this removes the need for it to be an R-B tree, an array is
tolerable here.

Adding an R-B tree not only has a memory overhead, but it then needs
more complex management when inserting, searching, etc.

Ian.