backends/confidential-guest-support: Add functions to support IGVM

In preparation for supporting the processing of IGVM files to configure
guests, this adds a set of functions to ConfidentialGuestSupport
allowing configuration of secure virtual machines that can be
implemented for each supported isolation platform type such as Intel TDX
or AMD SEV-SNP. These functions will be called by IGVM processing code
in subsequent patches.

This commit provides a default implementation of the functions that
either perform no action or generate an error when they are called.
Targets that support ConfidentalGuestSupport should override these
implementations.

Signed-off-by: Roy Hopkins <roy.hopkins@randomman.co.uk>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Gerd Hoffman <kraxel@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Ani Sinha <anisinha@redhat.com>
Link: https://lore.kernel.org/r/23e34a106da87427899f93178102e4a6ef50c966.1751554099.git.roy.hopkins@randomman.co.uk
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/backends/confidential-guest-support.c b/backends/confidential-guest-support.c
index 8ff7bfa857..c5bef1fbfa 100644
--- a/backends/confidential-guest-support.c
+++ b/backends/confidential-guest-support.c
@@ -14,15 +14,46 @@
 #include "qemu/osdep.h"
 
 #include "system/confidential-guest-support.h"
+#include "qapi/error.h"
 
 OBJECT_DEFINE_ABSTRACT_TYPE(ConfidentialGuestSupport,
                             confidential_guest_support,
                             CONFIDENTIAL_GUEST_SUPPORT,
                             OBJECT)
 
+static bool check_support(ConfidentialGuestPlatformType platform,
+                         uint16_t platform_version, uint8_t highest_vtl,
+                         uint64_t shared_gpa_boundary)
+{
+    /* Default: no support. */
+    return false;
+}
+
+static int set_guest_state(hwaddr gpa, uint8_t *ptr, uint64_t len,
+                           ConfidentialGuestPageType memory_type,
+                           uint16_t cpu_index, Error **errp)
+{
+    error_setg(errp,
+               "Setting confidential guest state is not supported for this platform");
+    return -1;
+}
+
+static int get_mem_map_entry(int index, ConfidentialGuestMemoryMapEntry *entry,
+                             Error **errp)
+{
+    error_setg(
+        errp,
+        "Obtaining the confidential guest memory map is not supported for this platform");
+    return -1;
+}
+
 static void confidential_guest_support_class_init(ObjectClass *oc,
                                                   const void *data)
 {
+    ConfidentialGuestSupportClass *cgsc = CONFIDENTIAL_GUEST_SUPPORT_CLASS(oc);
+    cgsc->check_support = check_support;
+    cgsc->set_guest_state = set_guest_state;
+    cgsc->get_mem_map_entry = get_mem_map_entry;
 }
 
 static void confidential_guest_support_init(Object *obj)