On Fri, Apr 17, 2020 at 12:09:38PM +0200, David Hildenbrand wrote:
> > What do you call "hinting ends" though? The fact we put
> > a page in the VQ is not a guarantee that it's been consumed
> > by the hypervisor.
> >
>
> I'd say hinting ends once the hypervisor sets FREE_PAGE_REPORT_S_DONE.
Can't find that one anywhere. what did I miss?
> >
> > I think a strict definition is this:
> > - hint includes a command ID
> > - hint implies "page was unused at some point after guest reading command ID"
> >
> >
> > Hypervisor can use dirty tracking tricks to get from that to
> > "page is unused at the moment".
> >
> >> Whereby X is
> >> currently assumed to be 0, correct?
> >
> >
> >
> > Now we are talking about what's safe to do with the page.
> >
> > If POISON flag is set by hypervisor but clear by guest,
> > or poison_val is 0, then it's clear it's safe to blow
> > away the page if we can figure out it's unused.
> >
> > Otherwise, it's much less clear :)
>
> Hah! Agreed :D
>
> >
> >
> >
> > I'll have to come back and re-read the rest next week, this
> > is complex stuff and I'm too rushed with other things today.
>
> Yeah, I'm also loaded with other stuff. Maybe Alex has time to
> understand the details as well.
>
> --
> Thanks,
>
> David / dhildenb
