Re: [PATCH v2 2/4] cxl/memdev: Hold memdev lock during memdev poison injection/clear

[Dave Jiang <dave.jiang@intel.com>]

On 4/21/26 3:48 AM, Li Ming wrote:
> 
> 在 2026/4/12 03:23, Dan Williams 写道:
>> Dave Jiang wrote:
>>>
>>> On 3/18/26 4:59 AM, Li Ming wrote:
>>>> 在 2026/3/17 23:00, Dave Jiang 写道:
>>>>> On 3/14/26 12:06 AM, Li Ming wrote:
>>>>>> CXL memdev poison injection/clearing debugfs interfaces are visible
>>>>>> before the CXL memdev endpoint initialization, If user accesses the
>>>>>> interfaces before cxlmd->endpoint updated, it is possible to access an
>>>>>> invalid endpoint in cxl_dpa_to_region().
>>>>>>
>>>>>> Hold CXL memdev lock at the beginning of the interfaces, this blocks the
>>>>>> interfaces until CXL memdev probing completed.
>>>>>>
>>>>>> The following patch will check the given endpoint validity in
>>>>>> cxl_dpa_to_region().
>>>>>>
>>>>>> Suggested-by: Dan Williams <dan.j.williams@intel.com>
>>>>>> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
>>>>>> Reviewed-by: Alison Schofield <alison.schofield@intel.com>
>>>>>> Signed-off-by: Li Ming <ming.li@zohomail.com>
>>>>> Hi Ming, I dropped this patch with Dan's comments [1] and updated cxl/next. Please check and make sure everything looks ok to you. Thanks!
>>>>>
>>>>> [1]: https://lore.kernel.org/linux-cxl/69b8b81621e16_452b100e@dwillia2-mobl4.notmuch/
>>>> Hi Dave,
>>>>
>>>> I think there is no change needed in this patch, just need a independent patch for holding memdev lock in cxl_region_debugfs_poison_inject/clear.
>>>>
>>>> Or you want to review this patch again?
>>> No. Maybe I misunderstood the comment from Dan. So we should keep this patch?
>> tl;dr: yes, this patch is *now* valid.
>>
>> As originally structured having patch2 before patch3 added no value.
>> Going forward I would say do not structure a series such that a new lock
>> taken in patch N starts being useful in patch N+1.
>>
>> I assume that is what:
>>
>> "The following patch will check the given endpoint validity in
>> cxl_dpa_to_region()."
>>
>> ...is trying to say, but when commits are applied to the tree it is
>> difficult to see that this commit was from a series.
>>
>> So do pick this one up, but the changelog needs adjusting. Something
>> like:
>>
>> "cxl_dpa_to_region() assumes that it is running a context where it is not
>> racing changes to "cxlmd->dev.driver". Acquire the memdev device lock in
>> the debugfs entry points to preclude debugfs usage racing cxl_mem driver
>> detach."
>>
>> With that you can add:
>>
>> Reviewed-by: Dan Williams <djbw@kernel.org>
> 
> Hi Dave,
> 
> Will you pick this patch with changes from Dan's comment? Or I need to send out a new version?

I believe it's merged into linus/master already. Can you check and see if everything looks correct?

> 
> 
> Ming
>