Re: [Qemu-devel] [RFC PATCH v1 06/22] sev: add initial SEV support

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Sep 14, 2016 at 11:10:54AM -0500, Brijesh Singh wrote:
> 
> > > Various commands and parameters are documented [1]
> > > 
> > > [1] http://support.amd.com/TechDocs/55766_SEV-KM%20API_Spec.pdf
> > 
> > If I understand correctly, the docs describe the firmware
> > interface. The interface provided by QEMU is not the same thing,
> > and needs to be documented as well (even if it contains pointers
> > to sections or tables in the firmware interface docs).
> > 
> > Some of the questions I have about the fields are:
> > * Do we really need the user to provide all the options below?
> >   * Can't QEMU or KVM calculate vcpu_count/vcpu_length/vcpu_mask,
> >     for example?
> 
> Good question, I don't think we need to get this information from guest
> owner and it can be calculated from KVM. I will check with security folks on
> how this information is used in measurement generation and make the changes
> accordingly.
> 
> > * Is bit 0 (KS) the only bit that can be set on flags? If so, why
> >   not a boolean "ks" option?
> Agreed. I will fix in v2.
> 
> > * Is "policy" the guest policy structure described at page 23? If
> >   so, why exposing the raw value instead of separate fields for
> >   each bit/field in the structure? (and only for the ones that
> >   are supposed to be set by the user)
> 
> Yes policy is described in chapter 3, page 23. I am open to separate the
> fields.
> Let me know if something like this works
> 
> sev-launch-rule,flags.ks=0,policy.dbg=0,policy.ks=0,policy.nosend=0,...

My question is, does all of it have to be sev specific?
For example, add a generic flag to block debug commands from monitor.
When blocked, and if sev happens to be enabled, you can run guest with
debug disabled.


-- 
MST