emulator: fail-fast on provision errors, diagnose smoke test failures

Provisioning used to silently wait out the full 6000s timeout on any
guest-side failure because the cleanup trap only logged the error. Now
it writes STACK_CLOUD_INIT_FAILED and shuts the VM down, and the host
waiter breaks on that marker and reports it distinctly.

Also bump smoke test timeout 120s->300s, dump docker ps / container
logs / free -m / verbose curl when it fails, log the qemu accel path,
and enable /dev/kvm on the CI runner so the VM isn't stuck in TCG.

.github/workflows/qemu-emulator-build.yaml

@@ -47,7 +47,20 @@ jobs:
       - name: Install QEMU dependencies
         run: |
           sudo apt-get update
-          sudo apt-get install -y qemu-system-x86 qemu-system-arm qemu-utils genisoimage socat qemu-efi-aarch64
+          sudo apt-get install -y qemu-system-x86 qemu-system-arm qemu-kvm qemu-utils genisoimage socat qemu-efi-aarch64
+
+      - name: Enable KVM access
+        run: |
+          echo 'KERNEL=="kvm", GROUP="kvm", MODE="0666", OPTIONS+="static_node=kvm"' \
+            | sudo tee /etc/udev/rules.d/99-kvm4all.rules
+          sudo udevadm control --reload-rules
+          sudo udevadm trigger --name-match=kvm || true
+          ls -la /dev/kvm || echo "no /dev/kvm present"
+          if [ -w /dev/kvm ]; then
+            echo "KVM is writable — hardware acceleration will be used"
+          else
+            echo "WARNING: /dev/kvm is not writable — will fall back to TCG (very slow)"
+          fi
 
       - name: Build QEMU image
         run: |

docker/local-emulator/qemu/build-image.sh

@@ -237,6 +237,7 @@ build_one() {
   local qemu_base pid elapsed total_build_lines
   local last_build_lines=0
   local guest_exited=false
+  local guest_failed=false
   local start_time=$SECONDS
 
   cp "$base_img" "$tmp_img"
@@ -258,6 +259,7 @@ build_one() {
   : > "$serial_log"
   : > "$provision_log"
   qemu_base="$(qemu_cmd_prefix_for_arch "$arch")"
+  log "QEMU command prefix (${arch}): $qemu_base"
 
   # shellcheck disable=SC2086
   $qemu_base \
@@ -282,6 +284,11 @@ build_one() {
       break
     fi
 
+    if contains_provision_marker "$provision_log" "$serial_log" "STACK_CLOUD_INIT_FAILED"; then
+      guest_failed=true
+      break
+    fi
+
     if [ -f "$provision_log" ]; then
       total_build_lines="$(line_count "$provision_log")"
       if [ "$total_build_lines" -gt "$last_build_lines" ]; then
@@ -308,7 +315,9 @@ build_one() {
   echo ""
 
   if ! contains_provision_marker "$provision_log" "$serial_log" "STACK_CLOUD_INIT_DONE"; then
-    if [ "$guest_exited" = true ]; then
+    if [ "$guest_failed" = true ]; then
+      err "Guest provisioning reported failure for emulator (${arch})"
+    elif [ "$guest_exited" = true ]; then
       err "Provisioning exited before completion for emulator (${arch})"
     else
       err "Provisioning timed out for emulator (${arch})"

docker/local-emulator/qemu/cloud-init/emulator/user-data

@@ -273,7 +273,7 @@ write_files:
         -v stack-inbucket-data:/data/inbucket \
         -d stack-local-emulator-slim
 
-      smoke_timeout=120
+      smoke_timeout=300
       smoke_elapsed=0
       smoke_passed=false
       while [ "$smoke_elapsed" -lt "$smoke_timeout" ]; do
@@ -286,13 +286,22 @@ write_files:
         smoke_elapsed=$((smoke_elapsed + 2))
       done
 
-      docker stop smoke-test 2>/dev/null || true
-      sleep 2
-
       if [ "$smoke_passed" = "false" ]; then
         log "SMOKE TEST FAILED: backend /health?db=1 did not return 200 within ${smoke_timeout}s"
+        log "--- docker ps -a ---"
+        docker ps -a 2>&1 | while IFS= read -r line; do log "ps: $line"; done || true
+        log "--- smoke-test container logs (last 200 lines) ---"
+        docker logs --tail 200 smoke-test 2>&1 | while IFS= read -r line; do log "smoke-test: $line"; done || true
+        log "--- free -m ---"
+        free -m 2>&1 | while IFS= read -r line; do log "mem: $line"; done || true
+        log "--- curl -v /health?db=1 ---"
+        curl -v --max-time 5 http://127.0.0.1:8102/health?db=1 2>&1 | while IFS= read -r line; do log "curl: $line"; done || true
+        docker stop smoke-test 2>/dev/null || true
         exit 1
       fi
+
+      docker stop smoke-test 2>/dev/null || true
+      sleep 2
       log "Smoke test passed (${smoke_elapsed}s)."
 
       log "Flattening image (docker export/import)..."
@@ -363,8 +372,17 @@ write_files:
 
       cleanup() {
         local status=$?
-        if [ "$status" -ne 0 ] && [ -n "${STACK_PROVISION_LOG_FILE:-}" ]; then
-          printf 'ERROR: provision-build exited with code %s\n' "$status" >> "$STACK_PROVISION_LOG_FILE"
+        if [ "$status" -ne 0 ]; then
+          if [ -n "${STACK_PROVISION_LOG_FILE:-}" ]; then
+            printf 'ERROR: provision-build exited with code %s\n' "$status" >> "$STACK_PROVISION_LOG_FILE"
+            printf '%s\n' "STACK_CLOUD_INIT_FAILED" >> "$STACK_PROVISION_LOG_FILE"
+          fi
+          for dev in /dev/console /dev/ttyAMA0 /dev/ttyS0; do
+            echo "STACK_CLOUD_INIT_FAILED" > "$dev" 2>/dev/null || true
+          done
+          sync || true
+          (sleep 2 && shutdown -P now) &
+          (sleep 15 && poweroff -f) &
         fi
       }
       trap cleanup EXIT