i386/sev: Introduce "sev-common" type to encapsulate common SEV state

Currently all SEV/SEV-ES functionality is managed through a single
'sev-guest' QOM type. With upcoming support for SEV-SNP, taking this
same approach won't work well since some of the properties/state
managed by 'sev-guest' is not applicable to SEV-SNP, which will instead
rely on a new QOM type with its own set of properties/state.

To prepare for this, this patch moves common state into an abstract
'sev-common' parent type to encapsulate properties/state that are
common to both SEV/SEV-ES and SEV-SNP, leaving only SEV/SEV-ES-specific
properties/state in the current 'sev-guest' type. This should not
affect current behavior or command-line options.

As part of this patch, some related changes are also made:

  - a static 'sev_guest' variable is currently used to keep track of
    the 'sev-guest' instance. SEV-SNP would similarly introduce an
    'sev_snp_guest' static variable. But these instances are now
    available via qdev_get_machine()->cgs, so switch to using that
    instead and drop the static variable.

  - 'sev_guest' is currently used as the name for the static variable
    holding a pointer to the 'sev-guest' instance. Re-purpose the name
    as a local variable referring the 'sev-guest' instance, and use
    that consistently throughout the code so it can be easily
    distinguished from sev-common/sev-snp-guest instances.

  - 'sev' is generally used as the name for local variables holding a
    pointer to the 'sev-guest' instance. In cases where that now points
    to common state, use the name 'sev_common'; in cases where that now
    points to state specific to 'sev-guest' instance, use the name
    'sev_guest'

In order to enable kernel-hashes for SNP, pull it from
SevGuestProperties to its parent SevCommonProperties so
it will be available for both SEV and SNP.

Signed-off-by: Michael Roth <michael.roth@amd.com>
Co-developed-by: Dov Murik <dovmurik@linux.ibm.com>
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
Acked-by: Markus Armbruster <armbru@redhat.com> (QAPI schema)
Co-developed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Signed-off-by: Pankaj Gupta <pankaj.gupta@amd.com>
Message-ID: <20240530111643.1091816-5-pankaj.gupta@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
3 files changed