Re: [PATCH Part2 RFC v4 22/40] KVM: SVM: Add KVM_SNP_INIT command

[Brijesh Singh]

On 7/16/21 2:33 PM, Sean Christopherson wrote:
> On Wed, Jul 07, 2021, Brijesh Singh wrote:
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 3fd9a7e9d90c..989a64aa1ae5 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -1678,6 +1678,9 @@ enum sev_cmd_id {
>>  	/* Guest Migration Extension */
>>  	KVM_SEV_SEND_CANCEL,
>>  
>> +	/* SNP specific commands */
>> +	KVM_SEV_SNP_INIT = 256,
> Is there any meaning behind '256'?  If not, why skip a big chunk?  I wouldn't be
> concerned if it weren't for KVM_SEV_NR_MAX, whose existence arguably implies that
> 0-KVM_SEV_NR_MAX-1 are all valid SEV commands.

In previous patches, Peter highlighted that we should keep some gap
between the SEV/ES and SNP to leave room for legacy SEV/ES expansion. I
was not sure how many we need to reserve without knowing what will come
in the future; especially recently some of the command additional  are
not linked to the firmware. I am okay to reduce the gap or remove the
gap all together.