Re: [PATCH -v3 1/3] resource: Fix region_intersects() vs add_memory_driver_managed()

[Huang, Ying]

Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes:

> On Fri,  6 Sep 2024 11:07:11 +0800 Huang Ying <ying.huang@xxxxxxxxx> wrote:
>
>> On a system with CXL memory, the resource tree (/proc/iomem) related
>> to CXL memory may look like something as follows.
>> 
>> 490000000-50fffffff : CXL Window 0
>>   490000000-50fffffff : region0
>>     490000000-50fffffff : dax0.0
>>       490000000-50fffffff : System RAM (kmem)
>> 
>> Because drivers/dax/kmem.c calls add_memory_driver_managed() during
>> onlining CXL memory, which makes "System RAM (kmem)" a descendant of
>> "CXL Window X".  This confuses region_intersects(), which expects all
>> "System RAM" resources to be at the top level of iomem_resource.  This
>> can lead to bugs.
>> 
>> ...
>> 
>> Fixes: c221c0b0308f ("device-dax: "Hotplug" persistent memory for use like normal RAM")
>
> Do you believe this should be fixed in earlier (-stable) kernels?

Yes.  I think that we should fix this in -stable kernels.  Although no
severe bug will be triggered on x86 in the earlier kernels, it may be a
real bug for some other architectures.

--
Best Regards,
Huang, Ying