kvm tools: Don't panic guest when exiting from custom rootfs

We currently panic guest when exiting from custom rootfs since at that point
we terminate init, and the guest kernel doesn't quite like that.

Instead, we do a graceful shutdown when init is done (either when 'lkvm
sandbox' command or '/bin/sh' is finished).

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

diff --git a/tools/kvm/guest/init_stage2.c b/tools/kvm/guest/init_stage2.c
index 6489fee18cac703baddbba592366a378a70b31de..7b96436a79162bd4037a77f1be4f8f0be5c6fda3 100644 (file)
--- a/tools/kvm/guest/init_stage2.c
+++ b/tools/kvm/guest/init_stage2.c
@@ -7,6 +7,7 @@
 #include <unistd.h>
 #include <stdio.h>
 #include <errno.h>
+#include <linux/reboot.h>
 
 static int run_process(char *filename)
 {
@@ -26,6 +27,9 @@ static int run_process_sandbox(char *filename)
 
 int main(int argc, char *argv[])
 {
+       pid_t child;
+       int status;
+
        /* get session leader */
        setsid();
 
@@ -34,12 +38,20 @@ int main(int argc, char *argv[])
 
        puts("Starting '/bin/sh'...");
 
-       if (access("/virt/sandbox.sh", R_OK) == 0)
-               run_process_sandbox("/bin/sh");
-       else
-               run_process("/bin/sh");
-
-       printf("Init failed: %s\n", strerror(errno));
+       child = fork();
+       if (child < 0) {
+               printf("Fatal: fork() failed with %d\n", child);
+               return 0;
+       } else if (child == 0) {
+               if (access("/virt/sandbox.sh", R_OK) == 0)
+                       run_process_sandbox("/bin/sh");
+               else
+                       run_process("/bin/sh");
+       } else {
+               wait(&status);
+       }
+
+       reboot(LINUX_REBOOT_CMD_RESTART);
 
        return 0;
 }