Re: [Libguestfs] [v2v PATCH 2/2] convert_windows: fix up the UEFI fallback boot loader if broken

The "fallback" (or "default") boot behavior is described at great length here: https://blog.uncooperative.org/uefi/linux/shim/efi%20system%20partition/2... The gist of it applies to all UEFI OSes, including Windows. For the fallback boot behavior to work, the \EFI\BOOT\BOOTX64.efi boot loader on the EFI system partition must match the installed operating system. We've encountered a physical machine, during a virt-p2v conversion, where (a) \EFI\BOOT\BOOTX64.efi belongs to a previously installed, but now wiped, RHEL (hence shim+grub) deployment, and (b) the currently installed operating system is Windows. Virt-v2v never transfers the UEFI variables (including the UEFI boot options) of the source, therefore the converted VM always relies on the default boot behavior when it is first started up. In the above scenario, where \EFI\BOOT\BOOTX64.efi is actually "shim", the mismatch is triggered at first boot after conversion, and a broken grub shell is reached instead of the Windows boot loader. Detect this situation by investigating \EFI\BOOT\BOOTX64.efi on the EFI system partition of a Windows disk image. If the file is missing, or is not -- as expected -- a duplicate of \EFI\Microsoft\Boot\bootmgfw.efi, then copy the latter to the former. Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2149629 Signed-off-by: Laszlo Ersek <lersek(a)redhat.com&gt; --- Notes: Tested with a freshly installed Win2019 guest whose \EFI\BOOT\BOOTX64.efi binary I manually corrupted. convert/convert_windows.ml | 25 ++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/convert/convert_windows.ml b/convert/convert_windows.ml index 34a5044dd338..57a7ff03398f 100644 --- a/convert/convert_windows.ml +++ b/convert/convert_windows.ml @@ -836,17 +836,42 @@ let convert (g : G.guestfs) _ inspect _ static_ips = ); with Not_found -> () + + and fix_win_uefi_fallback esp_path uefi_arch = + (* [esp_path] is on NTFS, and therefore it is considered case-sensitive; + * refer to + * <https://libguestfs.org/guestfs.3.html#guestfs_case_sensitive_path>;. + * However, the EFI system partition mounted under [esp_path] is FAT32 per + * UEFI spec, and the Linux vfat driver in the libguestfs appliance treats + * pathnames case-insensitively. Therefore, we're free to use any case in + * the ESP-relative pathnames below.

+ *) + let bootmgfw = sprintf "%s/efi/microsoft/boot/bootmgfw.efi" esp_path in + if g#is_file bootmgfw then + let bootdir = sprintf "%s/efi/boot" esp_path in + let fallback = sprintf "%s/boot%s.efi" bootdir uefi_arch in + if not (g#is_file fallback) || not (g#equal fallback bootmgfw) then (

+ info (f_"Fixing UEFI bootloader."); + g#rm_rf bootdir; + g#mkdir_p bootdir;

+ g#cp_a bootmgfw fallback + ) in match inspect.i_firmware with | I_BIOS -> () | I_UEFI esp_list -> let esp_temp_path = g#mkdtemp "/Windows/Temp/ESP_XXXXXX" in + let uefi_arch = get_uefi_arch_suffix inspect.i_arch in List.iter ( fun dev_path -> g#mount dev_path esp_temp_path; fix_win_uefi_bcd esp_temp_path; + (match uefi_arch with + | Some uefi_arch -> fix_win_uefi_fallback esp_temp_path uefi_arch + | None -> () + ); g#umount esp_temp_path; ) esp_list;