host: switch snapshot mapping to PAGE_READONLY (PR #1373)

host/Cargo.toml

@@ -27,13 +27,9 @@ name = "pyhl"
 path = "src/bin/pyhl.rs"
 
 [dependencies]
-# Point at danbugs/hyperlight snapshot-to-disk, which is upstream main
-# (the map_file_cow unaligned fix landed there) plus a squashed port of
 # hyperlight-dev/hyperlight#1373 — Ludvig's Snapshot::to_file/from_file
-# feature. We use it to persist a warmed-up sandbox on `pyhl setup` and
-# load it directly on every `pyhl run`, avoiding evolve + warmup per
-# invocation.
-hyperlight-host = { git = "https://github.com/danbugs/hyperlight", branch = "snapshot-to-disk", features = ["executable_heap", "hw-interrupts"] }
+# Uses PAGE_READONLY mapping (no host commit charge per VM).
+hyperlight-host = { git = "https://github.com/hyperlight-dev/hyperlight", branch = "disk_snapshot_copy", features = ["executable_heap", "hw-interrupts"] }
 clap = { version = "4", features = ["derive", "env"] }
 anyhow = "1"
 memmap2 = "0.9"

host/src/lib.rs

@@ -64,7 +64,7 @@ use hyperlight_host::func::Registerable;
 use hyperlight_host::sandbox::snapshot::Snapshot;
 use hyperlight_host::sandbox::uninitialized::GuestEnvironment;
 use hyperlight_host::sandbox::SandboxConfiguration;
-use hyperlight_host::{GuestBinary, MultiUseSandbox, UninitializedSandbox};
+use hyperlight_host::{GuestBinary, HostFunctions, MultiUseSandbox, UninitializedSandbox};
 use std::collections::HashMap;
 use std::path::Path;
 use std::sync::Arc;
@@ -1402,22 +1402,25 @@ impl Sandbox {
     pub fn from_snapshot_file_with<P: AsRef<Path>>(path: P, preopens: &[Preopen]) -> Result<Self> {
         let loaded = Snapshot::from_file_unchecked(path.as_ref())?;
         let arc = Arc::new(loaded);
-        let mut inner = MultiUseSandbox::from_snapshot(arc.clone())?;
 
-        // Wire up the fs_* tool handlers against the caller's preopens.
-        // The snapshot was warmed up with hostfs already mounted, so the
-        // guest will route fs_* calls through __dispatch → the FsRouter
-        // we install here.
+        let mut host_funcs = HostFunctions::default();
         if !preopens.is_empty() {
             if let Some(tools) = build_tools(None, preopens)? {
                 let tools = Arc::new(tools);
                 let tools_ref = tools.clone();
-                inner.register_host_function("__dispatch", move |payload: Vec<u8>| -> Vec<u8> {
-                    tools_ref.dispatch(&payload)
-                })?;
+                host_funcs
+                    .register_host_function("__dispatch", move |payload: Vec<u8>| -> Vec<u8> {
+                        tools_ref.dispatch(&payload)
+                    })?;
             }
+        } else {
+            host_funcs.register_host_function("__dispatch", |_payload: Vec<u8>| -> Vec<u8> {
+                Vec::new()
+            })?;
         }
 
+        let inner = MultiUseSandbox::from_snapshot(arc.clone(), host_funcs, None)?;
+
         Ok(Self {
             inner,
             snapshot: Some(arc),