Add --arch to run-windows11.py and download the Windows ISO with --download-only

Update vm-images: add a windows11 download target.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

run-windows11.py

@@ -77,85 +77,44 @@ def normalize_arch(arch):
     die(f"unsupported architecture: {arch}")
 
 
-host_arch = normalize_arch(env("VM_IMAGE_ARCH") or platform.machine())
-qemu_binary = "qemu-system-aarch64" if host_arch == "arm64" else "qemu-system-x86_64"
-host_os = platform.system().lower()
-if host_os == "darwin" and host_arch == "amd64":
-    die("amd64 guests are not supported on macOS hosts; use an arm64 image")
-qemu_platform_config = script_dir / "qemu" / f"windows11-{host_os}-{host_arch}.ini"
-
-
-def pick_firmware(override, *candidates):
-    if override:
-        return Path(override)
-    for candidate in candidates:
-        if Path(candidate).is_file():
-            return Path(candidate)
-    return Path(candidates[0])
-
-
-if host_arch == "arm64":
-    uefi_code = pick_firmware(
-        env("WIN11_VM_UEFI_CODE"),
-        "/usr/share/AAVMF/AAVMF_CODE.fd",
-        "/usr/share/edk2/aarch64/QEMU_EFI.fd",
-        "/opt/homebrew/share/qemu/edk2-aarch64-code.fd",
-        "/usr/local/share/qemu/edk2-aarch64-code.fd",
-    )
-    uefi_vars_template = pick_firmware(
-        env("WIN11_VM_UEFI_VARS"),
-        "/usr/share/AAVMF/AAVMF_VARS.fd",
-        "/usr/share/edk2/aarch64/vars-template-pflash.raw",
-        "/opt/homebrew/share/qemu/edk2-arm-vars.fd",
-        "/usr/local/share/qemu/edk2-arm-vars.fd",
-    )
-else:
-    uefi_code = pick_firmware(
-        env("WIN11_VM_UEFI_CODE"),
-        "/usr/share/OVMF/OVMF_CODE_4M.fd",
-        "/usr/share/edk2/ovmf/OVMF_CODE.fd",
-        "/opt/homebrew/share/qemu/edk2-x86_64-code.fd",
-        "/usr/local/share/qemu/edk2-x86_64-code.fd",
-    )
-    uefi_vars_template = pick_firmware(
-        env("WIN11_VM_UEFI_VARS"),
-        "/usr/share/OVMF/OVMF_VARS_4M.fd",
-        "/usr/share/edk2/ovmf/OVMF_VARS.fd",
-        "/opt/homebrew/share/qemu/edk2-i386-vars.fd",
-        "/usr/local/share/qemu/edk2-i386-vars.fd",
-    )
 daemonize = False
 install_from_iso = False
 install_from_img = False
 download_only = False
 extra_args = []
+arch_option = None
 
 
 def usage(stream=sys.stdout):
     stream.write(f"""\
 Usage: {Path(sys.argv[0]).name} [--daemon] [--download-only] [--install-from-iso | --install-from-img]
-       [--state-dir DIR] [--rdp-port PORT] [--ssh-port PORT] [-- QEMU_ARGUMENT ...]
+       [--arch ARCH] [--state-dir DIR] [--rdp-port PORT] [--ssh-port PORT] [-- QEMU_ARGUMENT ...]
 
 If the system disk (DIR/disk.qcow2, see --state-dir) is missing, create it from
 the Windows 11 QCOW2 base image.
 The VM hardware (accelerator, memory, CPUs, drives, devices) is defined in
 qemu/windows11.ini, which is rendered to qemu.ini in the state directory and
 loaded with QEMU's -readconfig, followed by qemu/windows11-<os>-<arch>.ini (os is linux or darwin, arch is amd64 or arm64, chosen from the host system and
-architecture or VM_IMAGE_ARCH). Later QEMU arguments override them, e.g. -- -m 4G -smp 4.
+architecture, --arch or VM_IMAGE_ARCH). Later QEMU arguments override them, e.g. -- -m 4G -smp 4.
 Use --install-from-iso to perform an automatic ISO installation instead, or
 --install-from-img to install from a disk image built from the ISO.
 If it exists, start Windows normally without attaching installation media.
 
 Options:
   --daemon            Run QEMU in the background
-  --download-only     Download the VirtIO tools ISO if it is missing, then exit
+  --download-only     Download the VirtIO tools ISO and the Windows 11 ISO
-                      (the Windows ISO and base QCOW2 are supplied manually)
+                      (for --arch) if they are missing, then exit; needs
+                      Node.js and Chromium for the latter, see vm-images/README.md
+                      (the base QCOW2 is supplied manually)
   --install-from-iso  Install from ISO when the system disk is missing
   --install-from-img  Like --install-from-iso, but install from the disk image
                       made by vm-images/build-windows-install-disk.sh, which
                       is the ISO path ending in .img instead of .iso.
                       It is attached as an NVMe disk, much faster than the
                       emulated USB CD-ROM, and is never modified
+  --arch ARCH         Guest architecture: arm64 or amd64 (default: the host's;
+                      overrides VM_IMAGE_ARCH). A guest that differs from the
+                      host runs under slow TCG emulation
   --state-dir DIR     Directory for the VM disk, seed ISO and runtime files
                       (default: .vm/windows11; overrides WIN11_VM_STATE_DIR)
   --rdp-port PORT     Host port forwarded to guest RDP (default: 3389;
@@ -212,6 +171,12 @@ while args:
             rdp_port = value
         else:
             ssh_port = value
+    elif arg == "--arch":
+        if not args:
+            die(f"{arg} requires an architecture argument.", 2)
+        arch_option = args.pop(0)
+    elif arg.startswith("--arch="):
+        arch_option = arg.split("=", 1)[1]
     elif arg in ("-h", "--help"):
         usage()
         sys.exit(0)
@@ -223,11 +188,62 @@ while args:
         usage(sys.stderr)
         sys.exit(2)
 
+host_arch = normalize_arch(arch_option or env("VM_IMAGE_ARCH") or platform.machine())
+# The shared image helper and build-seed.sh pick the architecture from here.
+os.environ["VM_IMAGE_ARCH"] = host_arch
+qemu_binary = "qemu-system-aarch64" if host_arch == "arm64" else "qemu-system-x86_64"
+host_os = platform.system().lower()
+if host_os == "darwin" and host_arch == "amd64":
+    die("amd64 guests are not supported on macOS hosts; use an arm64 image")
+qemu_platform_config = script_dir / "qemu" / f"windows11-{host_os}-{host_arch}.ini"
+
+
+def pick_firmware(override, *candidates):
+    if override:
+        return Path(override)
+    for candidate in candidates:
+        if Path(candidate).is_file():
+            return Path(candidate)
+    return Path(candidates[0])
+
+
+if host_arch == "arm64":
+    uefi_code = pick_firmware(
+        env("WIN11_VM_UEFI_CODE"),
+        "/usr/share/AAVMF/AAVMF_CODE.fd",
+        "/usr/share/edk2/aarch64/QEMU_EFI.fd",
+        "/opt/homebrew/share/qemu/edk2-aarch64-code.fd",
+        "/usr/local/share/qemu/edk2-aarch64-code.fd",
+    )
+    uefi_vars_template = pick_firmware(
+        env("WIN11_VM_UEFI_VARS"),
+        "/usr/share/AAVMF/AAVMF_VARS.fd",
+        "/usr/share/edk2/aarch64/vars-template-pflash.raw",
+        "/opt/homebrew/share/qemu/edk2-arm-vars.fd",
+        "/usr/local/share/qemu/edk2-arm-vars.fd",
+    )
+else:
+    uefi_code = pick_firmware(
+        env("WIN11_VM_UEFI_CODE"),
+        "/usr/share/OVMF/OVMF_CODE_4M.fd",
+        "/usr/share/edk2/ovmf/OVMF_CODE.fd",
+        "/opt/homebrew/share/qemu/edk2-x86_64-code.fd",
+        "/usr/local/share/qemu/edk2-x86_64-code.fd",
+    )
+    uefi_vars_template = pick_firmware(
+        env("WIN11_VM_UEFI_VARS"),
+        "/usr/share/OVMF/OVMF_VARS_4M.fd",
+        "/usr/share/edk2/ovmf/OVMF_VARS.fd",
+        "/opt/homebrew/share/qemu/edk2-i386-vars.fd",
+        "/usr/local/share/qemu/edk2-i386-vars.fd",
+    )
 if install_from_img:
     install_from_iso = True
 
 if download_only:
-    # The VirtIO tools ISO is the only medium the launcher downloads itself.
+    # The VirtIO tools ISO and the Windows installation ISO are the media the
+    # launcher downloads itself; the base QCOW2 is supplied manually.
+    image_downloader = None
     if env("WIN11_VM_TOOLS_ISO"):
         tools_iso = Path(env("WIN11_VM_TOOLS_ISO"))
         if not tools_iso.is_file():
@@ -240,6 +256,15 @@ if download_only:
         if not tools_iso.is_file():
             die(f"downloader did not create: {tools_iso}")
     print(f"VirtIO Windows tools ISO is ready: {tools_iso}")
+    if env("WIN11_VM_INSTALL_ISO"):
+        install_iso = Path(env("WIN11_VM_INSTALL_ISO"))
+        if not install_iso.is_file():
+            die(f"Windows 11 installation ISO was not found: {install_iso}")
+    else:
+        image_downloader = image_downloader or find_image_downloader()
+        run([str(image_downloader), "windows11"])
+        install_iso = Path(capture([str(image_downloader), "--print-path", "windows11", "--iso"]))
+    print(f"Windows 11 installation ISO is ready: {install_iso}")
     sys.exit(0)
 
 disk_image = Path(env("WIN11_VM_DISK_IMAGE") or state_dir / "disk.qcow2")