Re: [PATCH v6 4/7] crash_dump: reuse saved dm crypt keys for CPU/memory hot-plugging

Coiby Xu
2024-12-23T00:45:19Z

On Wed, Dec 11, 2024 at 09:08:43PM +0800, Baoquan He wrote:
>On 10/29/24 at 01:52pm, Coiby Xu wrote:
>> When there are CPU and memory hot un/plugs, the dm crypt keys may need
>> to be reloaded again depending on the solution for crash hotplug
>> support. Currently, there are two solutions. One is to utilizes udev to
>> instruct user space to reload the kdump kernel image and initrd,
>> elfcorehdr and etc again. The other is to only update the elfcorehdr
>> segment introduced in commit 247262756121 ("crash:
>> add generic infrastructure for crash hotplug support").
>>
>> For the 1st solution, the dm crypt keys need to be reloaded again. The
>> user space can write true to
>> /sys/kernel/config/crash_dm_crypt_key/reuse so the stored keys can be
>> re-used.
>>
>> For the 2nd solution, the dm crypt keys don't need to be reloaded.
>> Currently, only x86 supports the 2nd solution. If the 2nd solution
>> gets extended to all arches, this patch can be dropped.
>>
>> Signed-off-by: Coiby Xu <coxu@redhat.com>
>> ---
>> kernel/crash_dump_dm_crypt.c | 52 +++++++++++++++++++++++++++++++++---
>> 1 file changed, 48 insertions(+), 4 deletions(-)
>>
>> diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c
>> index ec2ec2967242..51431f93fc1e 100644
>> --- a/kernel/crash_dump_dm_crypt.c
>> +++ b/kernel/crash_dump_dm_crypt.c
>> @@ -28,6 +28,20 @@ static size_t get_keys_header_size(size_t total_keys)
>> return struct_size(keys_header, keys, total_keys);
>> }
>>
>> +static void get_keys_from_kdump_reserved_memory(void)
>> +{
>> + struct keys_header *keys_header_loaded;
>> +
>> + arch_kexec_unprotect_crashkres();
>> +
>> + keys_header_loaded = kmap_local_page(pfn_to_page(
>> + kexec_crash_image->dm_crypt_keys_addr >> PAGE_SHIFT));
>> +
>> + memcpy(keys_header, keys_header_loaded, get_keys_header_size(key_count));
>> + kunmap_local(keys_header_loaded);
>> + arch_kexec_protect_crashkres();
>> +}
>> +
>> static int read_key_from_user_keying(struct dm_crypt_key *dm_key)
>> {
>> const struct user_key_payload *ukp;
>> @@ -150,8 +164,36 @@ static ssize_t config_keys_count_show(struct config_item *item, char *page)
>>
>> CONFIGFS_ATTR_RO(config_keys_, count);
>>
>> +static bool reuse;
>
>Give it a meaningful name since it's a global variable, e.g
>is_dm_key_reused?

Sure, I'll use is_dm_key_reused in next version! Thanks for the
suggestion to improve code readability!

--
Best regards,
Coiby