Re: [PATCH V3] Documentation: Improve crash_kexec_post_notifiers description

["Guilherme G. Piccoli" <gpiccoli@igalia.com>]

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