sev/i386: add command to encrypt guest memory region

The KVM_SEV_LAUNCH_UPDATE_DATA command is used to encrypt a guest memory
region using the VM Encryption Key created using LAUNCH_START.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target/i386/sev.c

@@ -105,6 +105,13 @@ fw_error_to_str(int code)
     return sev_fw_errlist[code];
 }
 
+static bool
+sev_check_state(SevState state)
+{
+    assert(sev_state);
+    return sev_state->state == state ? true : false;
+}
+
 static void
 sev_set_guest_state(SevState new_state)
 {
@@ -486,6 +493,29 @@ sev_launch_start(SEVState *s)
     return 0;
 }
 
+static int
+sev_launch_update_data(uint8_t *addr, uint64_t len)
+{
+    int ret, fw_error;
+    struct kvm_sev_launch_update_data update;
+
+    if (!addr || !len) {
+        return 1;
+    }
+
+    update.uaddr = (__u64)(unsigned long)addr;
+    update.len = len;
+    trace_kvm_sev_launch_update_data(addr, len);
+    ret = sev_ioctl(sev_state->sev_fd, KVM_SEV_LAUNCH_UPDATE_DATA,
+                    &update, &fw_error);
+    if (ret) {
+        error_report("%s: LAUNCH_UPDATE ret=%d fw_error=%d '%s'",
+                __func__, ret, fw_error, fw_error_to_str(fw_error));
+    }
+
+    return ret;
+}
+
 void *
 sev_guest_init(const char *id)
 {
@@ -571,6 +601,19 @@ err:
     return NULL;
 }
 
+int
+sev_encrypt_data(void *handle, uint8_t *ptr, uint64_t len)
+{
+    assert(handle);
+
+    /* if SEV is in update state then encrypt the data else do nothing */
+    if (sev_check_state(SEV_STATE_LAUNCH_UPDATE)) {
+        return sev_launch_update_data(ptr, len);
+    }
+
+    return 0;
+}
+
 static void
 sev_register_types(void)
 {

target/i386/trace-events

@@ -12,3 +12,4 @@ kvm_memcrypt_register_region(void *addr, size_t len) "addr %p len 0x%zu"
 kvm_memcrypt_unregister_region(void *addr, size_t len) "addr %p len 0x%zu"
 kvm_sev_change_state(const char *old, const char *new) "%s -> %s"
 kvm_sev_launch_start(int policy, void *session, void *pdh) "policy 0x%x session %p pdh %p"
+kvm_sev_launch_update_data(void *addr, uint64_t len) "addr %p len 0x%" PRIu64