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

Raghavendra K T
2024-12-04T04:44:45Z

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@linux.intel.com> writes:
>>> On Tue, Dec 03, 2024 at 02:26:52PM +0800, Huang, Ying wrote:
>>>> Raghavendra K T <raghavendra.kt@amd.com> 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