Libguestfs - Jun 2016 - Re: [PATCH 2/2] v2v: remove the 'graphicsmodedisabled' entry in ESP BCD

On Fri, Jun 10, 2016 at 05:07:03PM +0300, Pavel Butsykin
wrote:
> Guest tools for Windows in Parallels / Virtuozzo Server 6 contain a
> paravirtualized video driver, which wants to take full control of the video
> mode. To avoid excessive video mode switches in UEFI VMs it executes
> "bcdedit /set {current} graphicsmodedisabled true".
> 
> When such a VM is imported into a QEMU/KVM-based hypervisor, the
> standard video drivers in Windows do not set the video mode as they
> expect it to have already been configured by the bootloader.  As a result,
> the VM runs with black screen.
> 
> So patch the BCD store (which is a Windows registry hive with a special
> structure, located on the EFI system partition) to clear this setting.
> 
> Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
> ---
>  v2v/convert_windows.ml | 41 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
> 
> diff --git a/v2v/convert_windows.ml b/v2v/convert_windows.ml
> index 62bb536..8579240 100644
> --- a/v2v/convert_windows.ml
> +++ b/v2v/convert_windows.ml
> @@ -466,6 +466,45 @@ if errorlevel 3010 exit /b 0
>          ignore (g#pwrite_device rootpart bytes 0x1a_L)
>        )
>      )
> +
> +  and fix_win_esp () > +    let fix_win_uefi_bcd esp_path > +     
try
> +        let bcd_path = "/EFI/Microsoft/Boot/BCD" in
> +        Windows.with_hive_write g (esp_path ^ bcd_path) (
> +          (* Remove the 'graphicsmodedisabled' key in BCD *)
> +          fun root ->
> +          let path = ["Objects";
"{9dea862c-5cdd-4e70-acc1-f32b344d4795}";
> +                      "Elements"; "23000003"] in
> +          let boot_mgr_default_link > +            match
Windows.get_node g root path with
> +            | None -> raise Not_found
> +            | Some node -> node in
> +          let current_boot_entry = g#hivex_value_utf8 (
> +            g#hivex_node_get_value boot_mgr_default_link
"Element") in
> +          let path = ["Objects"; current_boot_entry;
"Elements"; "16000046"] in
> +          match Windows.get_node g root path with
> +          | None -> raise Not_found
> +          | Some graphics_mode_disabled ->
> +            g#hivex_node_delete_child graphics_mode_disabled
> +        );
> +      with
> +        Not_found -> ()
> +    in
> +
> +    let esp_temp_path = g#mkdtemp "/Windows/Temp/ESP_XXXXXX" in
> +
> +    match inspect.i_uefi with
> +    | None -> ()
> +    | Some uefi_list ->
> +      List.iter (
> +        fun dev_path ->
> +        g#mount dev_path esp_temp_path;
> +        fix_win_uefi_bcd esp_temp_path;
> +        g#umount esp_temp_path;
> +      ) uefi_list;
> +
> +    g#rmdir esp_temp_path;
>    in
>  
>    (* Firstboot configuration. *)
> @@ -480,6 +519,8 @@ if errorlevel 3010 exit /b 0
>  
>    fix_ntfs_heads ();
>  
> +  fix_win_esp ();
> +
This patch looks OK to me.

Thanks,

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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