Re: [PATCH v2 for-4.14 1/3] xen/monitor: Control register values

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Jun 02, 2020 at 07:10:07AM -0600, Tamas K Lengyel wrote:
> On Tue, Jun 2, 2020 at 7:00 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
> >
> > On 02.06.2020 14:51, Tamas K Lengyel wrote:
> > > On Tue, Jun 2, 2020 at 6:47 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
> > >>
> > >> On 02.06.2020 14:40, Tamas K Lengyel wrote:
> > >>> On Tue, Jun 2, 2020 at 5:08 AM Roger Pau Monné <roger.pau@xxxxxxxxxx> 
> > >>> wrote:
> > >>>>
> > >>>> On Wed, May 20, 2020 at 08:31:52PM -0600, Tamas K Lengyel wrote:
> > >>>>> Extend the monitor_op domctl to include option that enables
> > >>>>> controlling what values certain registers are permitted to hold
> > >>>>> by a monitor subscriber.
> > >>>>
> > >>>> I think the change could benefit for some more detail commit message
> > >>>> here. Why is this useful?
> > >>>
> > >>> You would have to ask the Bitdefender folks who made the feature. I
> > >>> don't use it. Here we are just making it optional as it is buggy so it
> > >>> is disabled by default.
> > >>
> > >> Now that's exactly the opposite of what I had derived from the
> > >> description here so far. Perhaps an at least weak indication
> > >> that you want to reword this. For example, from your reply to
> > >> Roger I understand it's rather that the new flag allows to
> > >> "suppress" the controlling (since presumably you don't change
> > >> default behavior), rather then "enabling" it.
> > >
> > > What we are adding is a domctl you need to call that enables this
> > > feature. It's not an option to suppress it. It shouldn't have been
> > > enabled by default to begin with. That was a mistake when the feature
> > > was contributed and it is buggy.
> >
> > Okay, in this case it's important to point out that you alter
> > default behavior. The BitDefender folks may not like this, yet
> > they've been surprisingly silent so far.
> 
> Well, it was Bitdefender who altered the default behavior. We are
> reverting their mistake and making it optional. But I can certainly
> make that more clear.

I would like some input from the Bitdefender guys. Is there a bugfix
planned for this feature?

It would be nice to get this in before 4.14 releases.

Roger.