confidential guest support: Add kvm_init() and kvm_reset() in class

Different confidential VMs in different architectures all have the same
needs to do their specific initialization (and maybe resetting) stuffs
with KVM. Currently each of them exposes individual *_kvm_init()
functions and let machine code or kvm code to call it.

To facilitate the introduction of confidential guest technology from
different x86 vendors, add two virtual functions, kvm_init() and kvm_reset()
in ConfidentialGuestSupportClass, and expose two helpers functions for
invodking them.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Message-Id: <20240229060038.606591-1-xiaoyao.li@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/exec/confidential-guest-support.h

@@ -23,7 +23,10 @@
 #include "qom/object.h"
 
 #define TYPE_CONFIDENTIAL_GUEST_SUPPORT "confidential-guest-support"
-OBJECT_DECLARE_SIMPLE_TYPE(ConfidentialGuestSupport, CONFIDENTIAL_GUEST_SUPPORT)
+OBJECT_DECLARE_TYPE(ConfidentialGuestSupport,
+                    ConfidentialGuestSupportClass,
+                    CONFIDENTIAL_GUEST_SUPPORT)
+
 
 struct ConfidentialGuestSupport {
     Object parent;
@@ -55,8 +58,37 @@ struct ConfidentialGuestSupport {
 
 typedef struct ConfidentialGuestSupportClass {
     ObjectClass parent;
+
+    int (*kvm_init)(ConfidentialGuestSupport *cgs, Error **errp);
+    int (*kvm_reset)(ConfidentialGuestSupport *cgs, Error **errp);
 } ConfidentialGuestSupportClass;
 
+static inline int confidential_guest_kvm_init(ConfidentialGuestSupport *cgs,
+                                              Error **errp)
+{
+    ConfidentialGuestSupportClass *klass;
+
+    klass = CONFIDENTIAL_GUEST_SUPPORT_GET_CLASS(cgs);
+    if (klass->kvm_init) {
+        return klass->kvm_init(cgs, errp);
+    }
+
+    return 0;
+}
+
+static inline int confidential_guest_kvm_reset(ConfidentialGuestSupport *cgs,
+                                               Error **errp)
+{
+    ConfidentialGuestSupportClass *klass;
+
+    klass = CONFIDENTIAL_GUEST_SUPPORT_GET_CLASS(cgs);
+    if (klass->kvm_reset) {
+        return klass->kvm_reset(cgs, errp);
+    }
+
+    return 0;
+}
+
 #endif /* !CONFIG_USER_ONLY */
 
 #endif /* QEMU_CONFIDENTIAL_GUEST_SUPPORT_H */