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

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

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.

Tamas