[Libguestfs] [PATCH] v2v:windows: prevent Parallels drivers from loading at boot

[Richard W.M. Jones]

On Mon, Jun 06, 2016 at 03:12:36PM +0300, Roman Kagan wrote:
> Parallels proprietary hypervisor uses RDPMC as the hypercall
> instruction.  As this instruction is supported since early P6 family,
> the drivers didn't even bother to check for the presence of the
> corresponding feature in CPUID.
> 
> In QEMU/KVM, however, this instruction triggers #GP unless the VM is run
> with PMU (performance monitoring unit) enabled, which is often not the
> case (due to its impact on perfromance and migratability).
> 
> So, to prevent crashes upon conversion, stop respective drivers from
> loading by disabling the corresponding services.  Note that the services
> are being disabled ("Start" value set to 4) rather than their node
> removed, to avoid confusing the uninstaller which is scheduled to run
> from a firstboot script.
> 
> In addition, prl_strg (storage filter driver) is unlinked from the
> storage subsystem following the DelReg directive from its .inf file,
> otherwise Windows crashes with BSOD 0x7b due to missing dependency of
> the storage subsystem.
> 
> Signed-off-by: Roman Kagan <rkagan at virtuozzo.com>

ACK.

Rich.

>  v2v/convert_windows.ml | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 46 insertions(+)
> 
> diff --git a/v2v/convert_windows.ml b/v2v/convert_windows.ml
> index 49811a7..012f03d 100644
> --- a/v2v/convert_windows.ml
> +++ b/v2v/convert_windows.ml
> @@ -318,6 +318,7 @@ if errorlevel 3010 exit /b 0
>      debug "current ControlSet is %s" current_cs;
>  
>      disable_services root current_cs;
> +    disable_prl_drivers root current_cs;
>      disable_autoreboot root current_cs;
>      Windows_virtio.install_drivers g inspect systemroot
>                                     root current_cs rcaps
> @@ -344,6 +345,51 @@ if errorlevel 3010 exit /b 0
>             )
>           ) disable
>  
> +  and disable_prl_drivers root current_cs =
> +    (* Prevent Parallels drivers from loading at boot. *)
> +    let services = Windows.get_node g root [current_cs; "Services"] in
> +    let prl_svcs = [ "prl_boot"; "prl_dd"; "prl_eth5"; "prl_fs"; "prl_memdev";
> +                     "prl_mouf"; "prl_pv32"; "prl_pv64"; "prl_scsi";
> +                     "prl_sound"; "prl_strg"; "prl_tg"; "prl_time";
> +                     "prl_uprof"; "prl_va" ] in
> +
> +    match services with
> +    | None -> ()
> +    | Some services ->
> +        List.iter (
> +          fun svc ->
> +            let svc_node = g#hivex_node_get_child services svc in
> +            if svc_node <> 0L then (
> +              (* Disable the service rather than delete the node as it would
> +               * confuse the uninstaller called from firstboot script. *)
> +              g#hivex_node_set_value svc_node "Start" 4_L (le32_of_int 4_L)
> +            )
> +        ) prl_svcs;
> +
> +    (* perfrom the equivalent of DelReg from prl_strg.inf:
> +     * HKLM, System\CurrentControlSet\Control\Class\{4d36e967-e325-11ce-bfc1-08002be10318}, LowerFilters, 0x00018002, prl_strg
> +     *)
> +    let strg_cls = Windows.get_node g root
> +                        [current_cs; "Control"; "Class";
> +                         "{4d36e967-e325-11ce-bfc1-08002be10318}"] in
> +    match strg_cls with
> +    | None -> ()
> +    | Some strg_cls ->
> +        let lfkey = "LowerFilters" in
> +        let valueh = g#hivex_node_get_value strg_cls lfkey in
> +        if valueh <> 0L then (
> +          let data = g#hivex_value_value valueh in
> +          let filters = String.nsplit "\000" (Regedit.decode_utf16le data) in
> +          let filters = List.filter (
> +            fun x -> x <> "prl_strg" && x <> ""
> +          ) filters in
> +          let filters = List.map (
> +            fun x -> Regedit.encode_utf16le x ^ "\000\000"
> +          ) (filters @ [""]) in
> +          let data = String.concat "" filters in
> +          g#hivex_node_set_value strg_cls lfkey 7_L data
> +        )
> +
>    and disable_autoreboot root current_cs =
>      (* If the guest reboots after a crash, it's hard to see the original
>       * error (eg. the infamous 0x0000007B).  Turn off autoreboot.
> -- 
> 2.5.5
> 
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-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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