Enable hypervisor on pKVM builds
gs101 builds are getting experimental support for pKVM which can be
enabled either using fastboot or with misc_writer. For _pkvm builds we
want the device to automatically enable pKVM for testing. This patch
adds a new early-init service which checks for the presence of /dev/kvm
and if not found, writes to /misc and forces a reboot.
Bug: 192819132
Bug: 202484976
Test: flash a _pkvm build, observe double-reboot, check /dev/kvm exists
Change-Id: I3834b3e4c6118b3f6e4093ce52d5b94117eca29c
diff --git a/pkvm/pkvm_enabler.c b/pkvm/pkvm_enabler.c
new file mode 100644
index 0000000..cb14ba6
--- /dev/null
+++ b/pkvm/pkvm_enabler.c
@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "pkvm_enabler"
+
+#include <errno.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <log/log.h>
+
+#define KVM_DEVICE "/dev/kvm"
+#define MISC_WRITER "/vendor/bin/misc_writer"
+
+int main() {
+ char *newargv[] = { MISC_WRITER, "--set-enable-pkvm", NULL };
+ char *newenvp[] = { NULL };
+ pid_t pid;
+ int ret, wstatus;
+
+ /* Check whether KVM device exists. */
+ ret = access(KVM_DEVICE, F_OK);
+
+ /* If KVM device exists, return SUCCESS to continue booting. */
+ if (ret == 0) {
+ exit(EXIT_SUCCESS);
+ }
+
+ if (ret != -ENOENT) {
+ ALOGW("Unexpected error from access(): %d", ret);
+ }
+
+ /*
+ * If KVM device does not exist, run misc_writer and return FAILURE
+ * to force a reboot.
+ */
+ pid = fork();
+ if (pid == -1) {
+ ALOGE("Could not fork: %d", errno);
+ exit(EXIT_FAILURE);
+ }
+
+ if (pid == 0) {
+ execve(MISC_WRITER, newargv, newenvp);
+ ALOGE("Could not execute " MISC_WRITER ": %d", errno);
+ _exit(EXIT_FAILURE);
+ }
+
+ waitpid(pid, &wstatus, 0);
+ if (WIFEXITED(wstatus)) {
+ ret = WEXITSTATUS(wstatus);
+ if (ret) {
+ ALOGE(MISC_WRITER " exit status: %d", ret);
+ }
+ } else {
+ ALOGE(MISC_WRITER " terminated unexpectedly: %d", wstatus);
+ }
+
+ exit(EXIT_FAILURE);
+}