Re: [PATCH v5 8/9] crash_dump: Disallow configfs/crash_dm_crypt_key/reuse if crash hotplug supported
From: Randy Dunlap <rdunlap@infradead.org>
Date: 2026-09-09 05:46:08
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kexec, linux-doc, lkml
On 9/8/26 5:36 PM, Coiby Xu wrote:
quoted hunk ↗ jump to hunk
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 <redacted> Signed-off-by: Coiby Xu <redacted> --- 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,
echo yes > /sys/kernel/crash_dm_crypt_keys/restore +For CPU/memory hot-plugging, you can reuse keys already saved to reserved +memory before reloading the kdump image, + echo true > /sys/kernel/config/crash_dm_crypt_keys/reuse + +Note if crash hotplug is supported, this API is totally unnecessary thus will +be disabled automatically. + Contact =======
-- ~Randy