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>

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)

include/system/confidential-guest-support.h

@@ -19,6 +19,7 @@
 #define QEMU_CONFIDENTIAL_GUEST_SUPPORT_H
 
 #include "qom/object.h"
+#include "exec/hwaddr.h"
 
 #define TYPE_CONFIDENTIAL_GUEST_SUPPORT "confidential-guest-support"
 OBJECT_DECLARE_TYPE(ConfidentialGuestSupport,
@@ -26,6 +27,36 @@ OBJECT_DECLARE_TYPE(ConfidentialGuestSupport,
                     CONFIDENTIAL_GUEST_SUPPORT)
 
 
+typedef enum ConfidentialGuestPlatformType {
+    CGS_PLATFORM_SEV,
+    CGS_PLATFORM_SEV_ES,
+    CGS_PLATFORM_SEV_SNP,
+} ConfidentialGuestPlatformType;
+
+typedef enum ConfidentialGuestMemoryType {
+    CGS_MEM_RAM,
+    CGS_MEM_RESERVED,
+    CGS_MEM_ACPI,
+    CGS_MEM_NVS,
+    CGS_MEM_UNUSABLE,
+} ConfidentialGuestMemoryType;
+
+typedef struct ConfidentialGuestMemoryMapEntry {
+    uint64_t gpa;
+    uint64_t size;
+    ConfidentialGuestMemoryType type;
+} ConfidentialGuestMemoryMapEntry;
+
+typedef enum ConfidentialGuestPageType {
+    CGS_PAGE_TYPE_NORMAL,
+    CGS_PAGE_TYPE_VMSA,
+    CGS_PAGE_TYPE_ZERO,
+    CGS_PAGE_TYPE_UNMEASURED,
+    CGS_PAGE_TYPE_SECRETS,
+    CGS_PAGE_TYPE_CPUID,
+    CGS_PAGE_TYPE_REQUIRED_MEMORY,
+} ConfidentialGuestPageType;
+
 struct ConfidentialGuestSupport {
     Object parent;
 
@@ -64,6 +95,42 @@ typedef struct ConfidentialGuestSupportClass {
 
     int (*kvm_init)(ConfidentialGuestSupport *cgs, Error **errp);
     int (*kvm_reset)(ConfidentialGuestSupport *cgs, Error **errp);
+
+    /*
+     * Check to see if this confidential guest supports a particular
+     * platform or configuration.
+     *
+     * Return true if supported or false if not supported.
+     */
+    bool (*check_support)(ConfidentialGuestPlatformType platform,
+                         uint16_t platform_version, uint8_t highest_vtl,
+                         uint64_t shared_gpa_boundary);
+
+    /*
+     * Configure part of the state of a guest for a particular set of data, page
+     * type and gpa. This can be used for example to pre-populate and measure
+     * guest memory contents, define private ranges or set the initial CPU state
+     * for one or more CPUs.
+     *
+     * If memory_type is CGS_PAGE_TYPE_VMSA then ptr points to the initial CPU
+     * context for a virtual CPU. The format of the data depends on the type of
+     * confidential virtual machine. For example, for SEV-ES ptr will point to a
+     * vmcb_save_area structure that should be copied into guest memory at the
+     * address specified in gpa. The cpu_index parameter contains the index of
+     * the CPU the VMSA applies to.
+     */
+    int (*set_guest_state)(hwaddr gpa, uint8_t *ptr, uint64_t len,
+                           ConfidentialGuestPageType memory_type,
+                           uint16_t cpu_index, Error **errp);
+
+    /*
+     * Iterate the system memory map, getting the entry with the given index
+     * that can be populated into guest memory.
+     *
+     * Returns 0 for ok, 1 if the index is out of range and -1 on error.
+     */
+    int (*get_mem_map_entry)(int index, ConfidentialGuestMemoryMapEntry *entry,
+                             Error **errp);
 } ConfidentialGuestSupportClass;
 
 static inline int confidential_guest_kvm_init(ConfidentialGuestSupport *cgs,