[PATCH v5 8/9] crash_dump: Disallow configfs/crash_dm_crypt_key/reuse if crash hotplug supported

[Coiby Xu]

On Tue, Sep 08, 2026 at 10:46:03PM -0700, Randy Dunlap wrote:
>
>
>On 9/8/26 5:36 PM, Coiby Xu wrote:
>> If crash hotplug is supported, dm-crypt keys saved to reserved memory
>> will be taken care of automatically. Thus it doesn't make sense to use
>> configfs/crash_dm_crypt_key/reuse. Not reserving
>> image->dm_crypt_keys_addr makes it implicitly to disallow using this
>> API. Currently x86_64 and ppc64le have implemented crash hotplug
>> feature.
>>
>> Also update the doc accordingly. Note two doc issues are fixed as well.
>>
>> Fixes: 9ebfa8dcaea7 ("crash_dump: reuse saved dm crypt keys for CPU/memory hot-plugging")
>> Reviewed-by: Sourabh Jain <sourabhjain at linux.ibm.com>
>> Signed-off-by: Coiby Xu <coiby.xu at gmail.com>
>> ---
>>  Documentation/admin-guide/kdump/kdump.rst | 16 ++++++++++------
>>  kernel/crash_dump_dm_crypt.c              | 12 ++++++++----
>>  2 files changed, 18 insertions(+), 10 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
>> index 7587caadbae1..0bf2eb100a05 100644
>> --- a/Documentation/admin-guide/kdump/kdump.rst
>> +++ b/Documentation/admin-guide/kdump/kdump.rst
>> @@ -577,9 +577,10 @@ with /sys/kernel/config/crash_dm_crypt_keys for setup,
>>
>>  1. Tell the first kernel what logon keys are needed to unlock the disk volumes,
>>      # Add key #1
>> -    mkdir /sys/kernel/config/crash_dm_crypt_keys/7d26b7b4-e342-4d2d-b660-7426b0996720
>> +    VOL1_UUID=7d26b7b4-e342-4d2d-b660-7426b0996720
>> +    mkdir /sys/kernel/config/crash_dm_crypt_keys/$VOL1_UUID
>>      # Add key #1's description
>> -    echo cryptsetup:7d26b7b4-e342-4d2d-b660-7426b0996720 > /sys/kernel/config/crash_dm_crypt_keys/description
>> +    echo cryptsetup:$VOL1_UUID > /sys/kernel/config/crash_dm_crypt_keys/$VOL1_UUID/description
>>
>>      # how many keys do we have now?
>>      cat /sys/kernel/config/crash_dm_crypt_keys/count
>> @@ -591,15 +592,18 @@ with /sys/kernel/config/crash_dm_crypt_keys for setup,
>>      cat /sys/kernel/config/crash_dm_crypt_keys/count
>>      2
>>
>> -    # To support CPU/memory hot-plugging, reuse keys already saved to reserved
>> -    # memory
>> -    echo true > /sys/kernel/config/crash_dm_crypt_key/reuse
>> -
>>  2. Load the dump-capture kernel
>>
>>  3. After the dump-capture kerne get booted, restore the keys to user keyring
>
>                             kernel is booted,

Thanks for catching this typo! I'll apply your suggestion to next
version!

[...]

-- 
Best regards,
Coiby