Re: [PATCH v10 02/14] KVM: Cache as_id in kvm_memory_slot

Peter Xu
2020-07-07T20:38:34Z

On Tue, Jul 07, 2020 at 01:26:23PM -0700, Sean Christopherson wrote:
> On Tue, Jul 07, 2020 at 04:15:08PM -0400, Peter Xu wrote:
> > On Tue, Jul 07, 2020 at 12:56:58PM -0700, Sean Christopherson wrote:
> > > > > It's a single line of code, and there's more than one
> > > > > "shouldn't" in the above.
> > > >
> > > > If you want, I can both set it and add the comment. Thanks,
> > >
> > > Why bother with the comment? It'd be wrong in the sense that the as_id is
> > > always valid/accurate, even if npages == 0.
> >
> > Sorry I'm confused.. when npages==0, why as_id field is meaningful? Even if
> > the id field is meaningless after the slot is successfully removed, or am I
> > wrong?
> >
> > My understanding is that after your dynamic slot work, we'll only have at most
> > one extra memslot that was just removed, and that slot should be meaningless as
> > a whole. Feel free to correct me.
>
> Your understanding is correct. What I'm saying is that if something goes
> awry and the memslots need to be debugged, having accurate info for that one
> defunct memslot could be helpful, if only to not confuse a future debugger
> that doesn't fully understand memslots or address spaces. Sure, it could be
> manually added back in for debug, but it's literally a single line of code
> to carry and it avoids the need for a special comment.

Sure, will do. But again, I hope you allow me to add at least some comment.
To me, it's still weird to set these in a destroying memslot...

--
Peter Xu