cryptodev-builtin: Detect akcipher capability

Rather than exposing akcipher service/RSA algorithm to virtio crypto
device unconditionally, detect akcipher capability from akcipher
crypto framework. This avoids unsuccessful requests.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
Message-Id: <20230301105847.253084-7-pizhenwei@bytedance.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

backends/cryptodev-builtin.c

@@ -59,6 +59,19 @@ struct CryptoDevBackendBuiltin {
     CryptoDevBackendBuiltinSession *sessions[MAX_NUM_SESSIONS];
 };
 
+static void cryptodev_builtin_init_akcipher(CryptoDevBackend *backend)
+{
+    QCryptoAkCipherOptions opts;
+
+    opts.alg = QCRYPTO_AKCIPHER_ALG_RSA;
+    opts.u.rsa.padding_alg = QCRYPTO_RSA_PADDING_ALG_RAW;
+    if (qcrypto_akcipher_supports(&opts)) {
+        backend->conf.crypto_services |=
+                     (1u << QCRYPTODEV_BACKEND_SERVICE_AKCIPHER);
+        backend->conf.akcipher_algo = 1u << VIRTIO_CRYPTO_AKCIPHER_RSA;
+    }
+}
+
 static void cryptodev_builtin_init(
              CryptoDevBackend *backend, Error **errp)
 {
@@ -81,11 +94,9 @@ static void cryptodev_builtin_init(
     backend->conf.crypto_services =
                          1u << QCRYPTODEV_BACKEND_SERVICE_CIPHER |
                          1u << QCRYPTODEV_BACKEND_SERVICE_HASH |
-                         1u << QCRYPTODEV_BACKEND_SERVICE_MAC |
-                         1u << QCRYPTODEV_BACKEND_SERVICE_AKCIPHER;
+                         1u << QCRYPTODEV_BACKEND_SERVICE_MAC;
     backend->conf.cipher_algo_l = 1u << VIRTIO_CRYPTO_CIPHER_AES_CBC;
     backend->conf.hash_algo = 1u << VIRTIO_CRYPTO_HASH_SHA1;
-    backend->conf.akcipher_algo = 1u << VIRTIO_CRYPTO_AKCIPHER_RSA;
     /*
      * Set the Maximum length of crypto request.
      * Why this value? Just avoid to overflow when
@@ -94,6 +105,7 @@ static void cryptodev_builtin_init(
     backend->conf.max_size = LONG_MAX - sizeof(CryptoDevBackendOpInfo);
     backend->conf.max_cipher_key_len = CRYPTODEV_BUITLIN_MAX_CIPHER_KEY_LEN;
     backend->conf.max_auth_key_len = CRYPTODEV_BUITLIN_MAX_AUTH_KEY_LEN;
+    cryptodev_builtin_init_akcipher(backend);
 
     cryptodev_backend_set_ready(backend, true);
 }