backends/igvm: Process initialization sections in IGVM file

The initialization sections in IGVM files contain configuration that
should be applied to the guest platform before it is started. This
includes guest policy and other information that can affect the security
level and the startup measurement of a guest.

This commit introduces handling of the initialization sections during
processing of the IGVM file.

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>
Link: https://lore.kernel.org/r/9de24fb5df402024b40cbe02de0b13faa7cb4d84.1751554099.git.roy.hopkins@randomman.co.uk
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

backends/igvm.c

@@ -786,6 +786,27 @@ int qigvm_process_file(IgvmCfg *cfg, ConfidentialGuestSupport *cgs,
         }
     }
 
+    header_count =
+        igvm_header_count(ctx.file, IGVM_HEADER_SECTION_INITIALIZATION);
+    if (header_count < 0) {
+        error_setg(
+            errp,
+            "Invalid initialization header count in IGVM file. Error code: %X",
+            header_count);
+        goto cleanup_parameters;
+    }
+
+    for (ctx.current_header_index = 0;
+         ctx.current_header_index < (unsigned)header_count;
+         ctx.current_header_index++) {
+        IgvmVariableHeaderType type =
+            igvm_get_header_type(ctx.file, IGVM_HEADER_SECTION_INITIALIZATION,
+                                 ctx.current_header_index);
+        if (qigvm_handler(&ctx, type, errp) < 0) {
+            goto cleanup_parameters;
+        }
+    }
+
     /*
      * Contiguous pages of data with compatible flags are grouped together in
      * order to reduce the number of memory regions we create. Make sure the