Re: [RFC PATCH] resource: Fix CXL node not populated issue

[Raghavendra K T]

On 12/4/2024 8:31 AM, Andy Shevchenko wrote:
> On Wed, Dec 04, 2024 at 10:07:16AM +0800, Huang, Ying wrote:
> > Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> writes:
> > > On Tue, Dec 03, 2024 at 02:26:52PM +0800, Huang, Ying wrote:
> > > > Raghavendra K T <raghavendra.kt@xxxxxxx> writes:
>
> ...
>
> > > > > git bisect had led to below commit
> > > > > Fixes: b4afe4183ec7 ("resource: fix region_intersects() vs add_memory_driver_managed()")
> > > >
> > > > This breaks you case, sorry about that.  But this also fixed a real bug
> > > > too.  So, it's not appropriate just to revert it blindly.
> > >
> > > Linus was clear about this recently. Even if it fixes a bug, regression is
> > > still regression and might (*) lead to a revert.
> > > https://lwn.net/Articles/990599/
> > >
> > > (*) in general fixes are better than reverts, but depends on the timing in
> > >      the release cycle the revert may be the only option.
> >
> > I don't think that the timing is so tight that we should not work on
> > proper fix firstly.  I'm trying to work with the reporter on this.
>
> I agree on this, please do.
>
> > BTW, the commit b4afe4183ec7 ("resource: fix region_intersects() vs
> > add_memory_driver_managed()") fixed a security related bug.  The bug
> > weakened the protection to prevent users read/write system memory via
> > /dev/mem.  So, IMO, we need to be more careful about this.
>
> My point was that the regression is obvious and it needs to be fixed.
> That's all. Revert is a last resort in this sense.

I agree in general to both of your comment. (i.e. since this bisected
commit had security fix, we shall try to get better fix than a close to
revert).

 I am trying to work on this, but it is a bit slow on my side.


Thanks and Regards
- Raghu