Re: [Qemu-devel] [RFC PATCH v2 06/16] sev: add Secure Encrypted Virtulization (SEV) support

[Brijesh Singh]

Hi,

On 09/22/2016 10:12 AM, Paolo Bonzini wrote:
> >   to use encrypted guest launch
> >   # $QEMU \
> >      -object sev-receive-info,id=launch0 \
> >      -object sev-send-info,id=send0 \
> >      -object sev-guest-info,id=sev0,launch=launch0,send=send0 \
> >      .....
>
> References to other objects should be implemented as link properties
> (e.g. with type 'link<sev-guest-info>').  Then QOM takes care of filling
> in a QSEVGuestInfo* with the pointer to an object with the right id.
>
> There is some redundancy (e.g. "flags.ks" in launch/receive vs. "ks" in
> policy).  Can you document the full model in
> docs/amd-memory-encryption.txt?  It's not necessary to include the
> kernel API documentation.

The flags.ks means that hypervisor requested the key-sharing. The 
policy.ks means that key-sharing is allowed by guest owner. The values 
in sev-policy should be provided by the guest owner. The content of 
policy field is used during the measurement calculation. If hypervisor 
changes anything into policy field without guest owners permission then 
measurement value will not match.

I can think of one case where flag.ks may be used.

e.g lets say guest policy allows key sharing and this is first SEV guest 
in the system then hypervisor will set flags.ks=0. In next guest launch 
it can set flags.ks=1 and use the SEV handle from previous guest.

I will add some more text to clarify it in doc and property description.

> Paolo