[PATCH V3] Documentation: Improve crash_kexec_post_notifiers description
Guilherme G. Piccoli
gpiccoli at igalia.com
Sun Oct 27 13:43:22 PDT 2024
On 27/10/2024 15:16, Michael Kelley wrote:
> [...]
>> crash_kexec_post_notifiers
>> - Run kdump after running panic-notifiers and dumping
>> - kmsg. This only for the users who doubt kdump always
>> - succeeds in any situation.
>> - Note that this also increases risks of kdump failure,
>> - because some panic notifiers can make the crashed
>> - kernel more unstable.
>> + Only jump to kdump kernel after running the panic
>> + notifiers and dumping kmsg. This option increases
>> + the risks of a kdump failure, since some panic
>> + notifiers can make the crashed kernel more unstable.
>> + In configurations where kdump may not be reliable,
>> + running the panic notifiers could allow collecting
>> + more data on dmesg, like stack traces from other CPUS
>> + or extra data dumped by panic_print. Note that some
>> + configurations enable this option unconditionally,
>> + like Hyper-V, PowerPC (fadump) and AMD SEV.
>
> This last line should be more specific and use "AMD SEV-SNP" instead of
> just "AMD SEV". Commit 8ef979584ea8 that you mentioned above is
> specific to SEV-SNP.
>
> There have been three versions of SEV functionality in AMD processors:
> * SEV: the original guest VM encryption
> * SEV-ES: SEV enhanced to cover register state as well
> * SEV-SNP: SEV-ES plus Secure Nested Paging, which provides
> functionality to address the Confidential Computing VM threat model
> described in the Linux CoCo VM documentation. SEV-SNP processors are
> AMD's product that is widely deployed for CoCo VMs in large public clouds.
>
> Just using "SEV" is somewhat ambiguous because it's not clear whether
> it refers to the family of three SEV levels, or just the original guest VM
> encryption. Since this case is clearly SEV-SNP only, being specific removes
> the ambiguity.
>
> Michael
Thanks a lot Michael, for the clarification. I've just sent a V4
updating that.
Cheers,
Guilherme
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