Re: [PATCH] kvm/sev: make SEV/SEV-ES asids configurable

José Pekkarinen
2023-10-10T18:03:49Z

On 2023-10-10 19:49, Peter Gonda wrote:
> On Tue, Oct 10, 2023 at 5:22 AM José Pekkarinen
> <jose.pekkarinen@foxhound.fi> wrote:
>>
>> There are bioses that doesn't allow to configure the
>> number of asids allocated for SEV/SEV-ES, for those
>> cases, the default behaviour allocates all the asids
>> for SEV, leaving no room for SEV-ES to have some fun.
>> If the user request SEV-ES to be enabled, it will
>> find the kernel just run out of resources and ignored
>> user request. This following patch will address this
>> issue by making the number of asids for SEV/SEV-ES
>> configurable over kernel module parameters.
>>
>
> All this patch does is introduce an error case right? Because if the
> BIOS hasn't actually configured those SEV-ES asids and KVM tries to
> use an SEV as an SEV-ES asid commands to the ASP will fail, right?
>
> What happens when you try to create an SEV-ES VM with this patch, when
> the BIOS hasn't allocated any SEV-ES asids?

It still doesn't enable SEV-ES since the cpu exposes
min_sev_asids as 1, and there is a check to bail out in
the hardware setup function, so definitely this is not
fixing anything. I may not being understanding something
here though, since my BIOS doesn't seem to have any options
nor hints about SEV-ES, so I'm not quite sure it really
does something to provide the functionality. For the records
it is a Supermicro H11SSL-NC.

Thanks!

José.