Re: [PATCH v4 5/5] KVM: SEV: Add SEV-SNP CipherTextHiding support

[Kalra, Ashish]

On 5/23/2025 12:29 PM, Dave Hansen wrote:
> On 5/19/25 17:02, Ashish Kalra wrote:
>> +	kvm-amd.ciphertext_hiding_nr_asids=
>> +			[KVM,AMD] Enables SEV-SNP CipherTextHiding feature and
>> +			controls show many ASIDs are available for SEV-SNP guests.
>> +			The ASID space is basically split into legacy SEV and
>> +			SEV-ES+. CipherTextHiding feature further splits the
>> +			SEV-ES+ ASID space into SEV-ES and SEV-SNP.
>> +			If the value is -1, then it is used as an auto flag
>> +			and splits the ASID space equally between SEV-ES and
>> +			SEV-SNP ASIDs.
> 
> This help text isn't great.
> 
> It doesn't come out and say what the connection between CipherTextHiding
> and SEV-ES+. It's also impossible to choose a good number without
> knowing how large the ASID space is in the first place.
> 
> Why use "-1"? Why not just take "auto" as a parameter?
> 
> It also needs to say what CipherTextHiding is in the first place and be
> more clear about what the tradeoffs are from enabling this.
> 
> 

Sure, i will work on improving the documentation.

Sean, looking forward to your review and feedback on these patch-series, especially the KVM side of patches.

Thanks,
Ashish