Re: [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@xxxxxxxxxxxxx>
> > Signed-off-by: Coiby Xu <coiby.xu@xxxxxxxxx>
> > ---
> >  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