Mount overlay with nvidia libraries

Nvidia libraries must match the kernel module version. To avoid
the need to rebuild app containers frequently, mount nvidia libraries
as an overlay over base image.

runtime/init-container/src/init.c

@@ -1996,8 +1996,15 @@ int main(int argc, char **argv) {
     CHECK(mkdir("/mnt/overlay/work", S_IRWXU));
 
     CHECK(mount("/dev/vda", "/mnt/image", "squashfs", MS_RDONLY, ""));
-    CHECK(mount("overlay", SYSROOT, "overlay", 0,
-                "lowerdir=/mnt/image,upperdir=/mnt/overlay/upper,workdir=/mnt/overlay/work"));
+    if (access("/dev/vdb", R_OK) == 0) {
+        CHECK(mkdir("/mnt/gpu-files", S_IRWXU));
+        CHECK(mount("/dev/vdb", "/mnt/gpu-files", "squashfs", MS_RDONLY, ""));
+        CHECK(mount("overlay", SYSROOT, "overlay", 0,
+                    "lowerdir=/mnt/image:/mnt/gpu-files,upperdir=/mnt/overlay/upper,workdir=/mnt/overlay/work"));
+    } else {
+        CHECK(mount("overlay", SYSROOT, "overlay", 0,
+                    "lowerdir=/mnt/image,upperdir=/mnt/overlay/upper,workdir=/mnt/overlay/work"));
+    }
 
     g_sysroot_fd = CHECK(open(SYSROOT, O_RDONLY | O_DIRECTORY | O_CLOEXEC));
     assert(g_sysroot_fd >= 3);

runtime/src/vmrt.rs

@@ -21,6 +21,7 @@ const DIR_RUNTIME: &str = "runtime";
 const FILE_RUNTIME: &str = "vmrt";
 const FILE_VMLINUZ: &str = "vmlinuz-virt";
 const FILE_INITRAMFS: &str = "initramfs.cpio.gz";
+const FILE_NVIDIA_FILES: &str = "nvidia-files.squashfs";
 
 #[derive(Default)]
 pub struct RuntimeData {
@@ -115,6 +116,13 @@ pub async fn start_vmrt(
         cmd.arg("none");
     }
 
+    if Path::new(FILE_NVIDIA_FILES).exists() {
+        cmd.arg("-drive");
+        cmd.arg(format!(
+            "file={},cache=unsafe,readonly=on,format=raw,if=virtio",
+            FILE_NVIDIA_FILES).as_str());
+    }
+
     let (vpn, inet) =
     // backward-compatibility mode
     if vpn_remote.is_none() && inet_remote.is_none() {