[PATCH v2 15/22] target/arm/kvm-rme: Add measurement algorithm property

[Jean-Philippe Brucker]

This option selects which measurement algorithm to use for attestation.
Supported values are SHA256 and SHA512. Default to SHA512 arbitrarily.

SHA512 is generally faster on 64-bit architectures. On a few arm64 CPUs
I tested SHA256 is much faster, but that's most likely because they only
support acceleration via FEAT_SHA256 (Armv8.0) and not FEAT_SHA512
(Armv8.2). Future CPUs supporting RME are likely to also support
FEAT_SHA512.

Cc: Eric Blake <ebl...@redhat.com>
Cc: Markus Armbruster <arm...@redhat.com>
Cc: Daniel P. Berrangé <berra...@redhat.com>
Cc: Eduardo Habkost <edua...@habkost.net>
Signed-off-by: Jean-Philippe Brucker <jean-phili...@linaro.org>
---
v1->v2: use enum, pick default
---
 qapi/qom.json        | 18 +++++++++++++++++-
 target/arm/kvm-rme.c | 39 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/qapi/qom.json b/qapi/qom.json
index 91654aa267..84dce666b2 100644
--- a/qapi/qom.json
+++ b/qapi/qom.json
@@ -931,18 +931,34 @@
   'data': { '*cpu-affinity': ['uint16'],
             '*node-affinity': ['uint16'] } }
 
+##
+# @RmeGuestMeasurementAlgo:
+#
+# @sha256: Use the SHA256 algorithm
+# @sha512: Use the SHA512 algorithm
+#
+# Algorithm to use for realm measurements
+#
+# Since: FIXME
+##
+{ 'enum': 'RmeGuestMeasurementAlgo',
+  'data': ['sha256', 'sha512'] }
+
 ##
 # @RmeGuestProperties:
 #
 # Properties for rme-guest objects.
 #
+# @measurement-algo: Realm measurement algorithm (default: sha512)
+#
 # @personalization-value: Realm personalization value, as a 64-byte hex string
 #     (default: 0)
 #
 # Since: FIXME
 ##
 { 'struct': 'RmeGuestProperties',
-  'data': { '*personalization-value': 'str' } }
+  'data': { '*personalization-value': 'str',
+            '*measurement-algo': 'RmeGuestMeasurementAlgo' } }
 
 ##
 # @ObjectType:
diff --git a/target/arm/kvm-rme.c b/target/arm/kvm-rme.c
index cb5c3f7a22..8f39e54aaa 100644
--- a/target/arm/kvm-rme.c
+++ b/target/arm/kvm-rme.c
@@ -23,13 +23,14 @@ OBJECT_DECLARE_SIMPLE_TYPE(RmeGuest, RME_GUEST)
 
 #define RME_PAGE_SIZE qemu_real_host_page_size()
 
-#define RME_MAX_CFG         1
+#define RME_MAX_CFG         2
 
 struct RmeGuest {
     ConfidentialGuestSupport parent_obj;
     Notifier rom_load_notifier;
     GSList *ram_regions;
     uint8_t *personalization_value;
+    RmeGuestMeasurementAlgo measurement_algo;
 };
 
 typedef struct {
@@ -73,6 +74,19 @@ static int rme_configure_one(RmeGuest *guest, uint32_t cfg, 
Error **errp)
         memcpy(args.rpv, guest->personalization_value, 
KVM_CAP_ARM_RME_RPV_SIZE);
         cfg_str = "personalization value";
         break;
+    case KVM_CAP_ARM_RME_CFG_HASH_ALGO:
+        switch (guest->measurement_algo) {
+        case RME_GUEST_MEASUREMENT_ALGO_SHA256:
+            args.hash_algo = KVM_CAP_ARM_RME_MEASUREMENT_ALGO_SHA256;
+            break;
+        case RME_GUEST_MEASUREMENT_ALGO_SHA512:
+            args.hash_algo = KVM_CAP_ARM_RME_MEASUREMENT_ALGO_SHA512;
+            break;
+        default:
+            g_assert_not_reached();
+        }
+        cfg_str = "hash algorithm";
+        break;
     default:
         g_assert_not_reached();
     }
@@ -338,12 +352,34 @@ static void rme_set_rpv(Object *obj, const char *value, 
Error **errp)
     }
 }
 
+static int rme_get_measurement_algo(Object *obj, Error **errp)
+{
+    RmeGuest *guest = RME_GUEST(obj);
+
+    return guest->measurement_algo;
+}
+
+static void rme_set_measurement_algo(Object *obj, int algo, Error **errp)
+{
+    RmeGuest *guest = RME_GUEST(obj);
+
+    guest->measurement_algo = algo;
+}
+
 static void rme_guest_class_init(ObjectClass *oc, void *data)
 {
     object_class_property_add_str(oc, "personalization-value", rme_get_rpv,
                                   rme_set_rpv);
     object_class_property_set_description(oc, "personalization-value",
             "Realm personalization value (512-bit hexadecimal number)");
+
+    object_class_property_add_enum(oc, "measurement-algo",
+                                   "RmeGuestMeasurementAlgo",
+                                   &RmeGuestMeasurementAlgo_lookup,
+                                   rme_get_measurement_algo,
+                                   rme_set_measurement_algo);
+    object_class_property_set_description(oc, "measurement-algo",
+            "Realm measurement algorithm ('sha256', 'sha512')");
 }
 
 static void rme_guest_instance_init(Object *obj)
@@ -353,6 +389,7 @@ static void rme_guest_instance_init(Object *obj)
         exit(1);
     }
     rme_guest = RME_GUEST(obj);
+    rme_guest->measurement_algo = RME_GUEST_MEASUREMENT_ALGO_SHA512;
 }
 
 static const TypeInfo rme_guest_info = {
-- 
2.44.0