Re: [PATCH] RFC: alias rework

[Marcelo Tosatti <mtosatti@redhat.com>]

On Mon, Jan 25, 2010 at 10:40:32PM +0200, Izik Eidus wrote:
> On Mon, 25 Jan 2010 18:20:39 -0200
> Marcelo Tosatti <mtosatti@redhat.com> wrote:
> 
> > With current code, if a memslot is deleted, access through any aliases
> > that use it will fail (BTW it looks this is not properly handled, but
> > thats a separate problem).
> 
> 
> Yea I had some still open concerns about this code (this why I sent it on RFC)
> 
> > 
> > So AFAICS there is no requirement for an alias to continue "operable" 
> > if its parent memslot is deleted.
> 
> 
> With this patch alias will stop to opearte when the parent is deleted
> just like the behivor with the current code...
> 
> base_gfn will be set to 0 and npages will be set to 0 as well
> (the true values wil be hide in real_base_gfn...), so gfn_to_memslot
> and gfn_to_page will fail....

But you adjust the alias (and keep it valid) if dirty logging is
enabled?

> > 
> > Or is this a feature you need?
> 
> 
> I dont need it (I asked Avi to do something), So he said he want to nuke the aliasing
> from kvm and keep supporting the old userspace`s

With feature i meant keeping the alias around when parent slot is
deleted.

> Do you have any other way to achive this?

No.

> Btw I do realize it might be better not to push this patch and just keep the old
> way of treating aliasing as we have now, I really don`t mind.
> 
> > 
> > Motivation is that nukeing aliases is simpler than adjusting them.
> > 
> 
> Agree.