[PATCH v4 16/17] i386/sev: Add implementation of CGS set_guest_policy()

[Roy Hopkins]

The new cgs_set_guest_policy() function is provided to receive the guest
policy flags, SNP ID block and SNP ID authentication from guest
configuration such as an IGVM file and apply it to the platform prior to
launching the guest.

The policy is used to populate values for the existing 'policy',
'id_block' and 'id_auth' parameters. When provided, the guest policy is
applied and the ID block configuration is used to verify the launch
measurement and signatures. The guest is only successfully started if
the expected launch measurements match the actual measurements and the
signatures are valid.

Signed-off-by: Roy Hopkins <roy.hopkins@suse.com>
---
 target/i386/sev.h | 12 +++++++
 target/i386/sev.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+)

diff --git a/target/i386/sev.h b/target/i386/sev.h
index 2ccd6fe1e8..7b92102bd0 100644
--- a/target/i386/sev.h
+++ b/target/i386/sev.h
@@ -157,6 +157,18 @@ struct QEMU_PACKED sev_es_save_area {
     uint8_t fpreg_ymm[256];
 };
 
+struct QEMU_PACKED sev_snp_id_authentication {
+    uint32_t id_key_alg;
+    uint32_t auth_key_algo;
+    uint8_t reserved[56];
+    uint8_t id_block_sig[512];
+    uint8_t id_key[1028];
+    uint8_t reserved2[60];
+    uint8_t id_key_sig[512];
+    uint8_t author_key[1028];
+    uint8_t reserved3[892];
+};
+
 #ifdef CONFIG_SEV
 bool sev_enabled(void);
 bool sev_es_enabled(void);
diff --git a/target/i386/sev.c b/target/i386/sev.c
index 9a05b971c8..c4d0682d75 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -2446,6 +2446,88 @@ static int cgs_get_mem_map_entry(int index,
     return 0;
 }
 
+static int cgs_set_guest_policy(ConfidentialGuestPolicyType policy_type,
+                                uint64_t policy, void *policy_data1,
+                                uint32_t policy_data1_size, void *policy_data2,
+                                uint32_t policy_data2_size, Error **errp)
+{
+    if (policy_type != GUEST_POLICY_SEV) {
+        error_setg(errp, "%s: Invalid guest policy type provided for SEV: %d",
+        __func__, policy_type);
+        return -1;
+    }
+    /*
+     * SEV-SNP handles policy differently. The policy flags are defined in
+     * kvm_start_conf.policy and an ID block and ID auth can be provided.
+     */
+    if (sev_snp_enabled()) {
+        SevSnpGuestState *sev_snp_guest =
+            SEV_SNP_GUEST(MACHINE(qdev_get_machine())->cgs);
+        struct kvm_sev_snp_launch_finish *finish =
+            &sev_snp_guest->kvm_finish_conf;
+
+        /*
+         * The policy consists of flags in 'policy' and optionally an ID block
+         * and ID auth in policy_data1 and policy_data2 respectively. The ID
+         * block and auth are optional so clear any previous ID block and auth
+         * and set them if provided, but always set the policy flags.
+         */
+        g_free(sev_snp_guest->id_block);
+        g_free((guchar *)finish->id_block_uaddr);
+        g_free(sev_snp_guest->id_auth);
+        g_free((guchar *)finish->id_auth_uaddr);
+        sev_snp_guest->id_block = NULL;
+        finish->id_block_uaddr = 0;
+        sev_snp_guest->id_auth = NULL;
+        finish->id_auth_uaddr = 0;
+
+        if (policy_data1_size > 0) {
+            struct sev_snp_id_authentication *id_auth =
+                (struct sev_snp_id_authentication *)policy_data2;
+
+            if (policy_data1_size != KVM_SEV_SNP_ID_BLOCK_SIZE) {
+                error_setg(errp, "%s: Invalid SEV-SNP ID block: incorrect 
size",
+                           __func__);
+                return -1;
+            }
+            if (policy_data2_size != KVM_SEV_SNP_ID_AUTH_SIZE) {
+                error_setg(errp,
+                           "%s: Invalid SEV-SNP ID auth block: incorrect size",
+                           __func__);
+                return -1;
+            }
+            assert(policy_data1 != NULL);
+            assert(policy_data2 != NULL);
+
+            finish->id_block_uaddr =
+                (__u64)g_memdup2(policy_data1, KVM_SEV_SNP_ID_BLOCK_SIZE);
+            finish->id_auth_uaddr =
+                (__u64)g_memdup2(policy_data2, KVM_SEV_SNP_ID_AUTH_SIZE);
+
+            /*
+             * Check if an author key has been provided and use that to flag
+             * whether the author key is enabled. The first of the author key
+             * must be non-zero to indicate the key type, which will currently
+             * always be 2.
+             */
+            sev_snp_guest->kvm_finish_conf.auth_key_en =
+                id_auth->author_key[0] ? 1 : 0;
+            finish->id_block_en = 1;
+        }
+        sev_snp_guest->kvm_start_conf.policy = policy;
+    } else {
+        SevGuestState *sev_guest = SEV_GUEST(MACHINE(qdev_get_machine())->cgs);
+        /* Only the policy flags are supported for SEV and SEV-ES */
+        if ((policy_data1_size > 0) || (policy_data2_size > 0) || !sev_guest) {
+            error_setg(errp, "%s: An ID block/ID auth block has been provided "
+                             "but SEV-SNP is not enabled", __func__);
+            return -1;
+        }
+        sev_guest->policy = policy;
+    }
+    return 0;
+}
+
 static void
 sev_common_class_init(ObjectClass *oc, void *data)
 {
@@ -2484,6 +2566,7 @@ sev_common_instance_init(Object *obj)
     cgs->check_support = cgs_check_support;
     cgs->set_guest_state = cgs_set_guest_state;
     cgs->get_mem_map_entry = cgs_get_mem_map_entry;
+    cgs->set_guest_policy = cgs_set_guest_policy;
 
     QTAILQ_INIT(&sev_common->launch_vmsa);
 }
-- 
2.43.0