Re: [Xen-devel] [PATCH v2] libxl: make vkbd tunable for HVM guests

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, May 07, 2019 at 01:53:20PM +0000, Eslam Elnikety wrote:
> Each HVM guest currently gets a vkbd frontend/backend pair (c/s ebbd2561b4c).
> This consumes host resources unnecessarily for guests that have no use for
> vkbd. Make this behaviour tunable to allow an administrator to choose. The
> commit retains the current behaviour -- HVM guests still get vkdb unless
> specified otherwise.
> 
> Signed-off-by: Eslam Elnikety <elnikety@xxxxxxxxxx>
> 
> ---
>     Changes in v2:
>         - Added a missing hunk / setting vkb_device per config
> ---
>  tools/libxl/libxl_create.c  | 9 ++++++---
>  tools/libxl/libxl_types.idl | 1 +
>  tools/xl/xl_parse.c         | 1 +
>  tools/xl/xl_sxp.c           | 2 ++
>  4 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
> index 89fe80fc9c..03ce166f4f 100644
> --- a/tools/libxl/libxl_create.c
> +++ b/tools/libxl/libxl_create.c
> @@ -310,6 +310,7 @@ int libxl__domain_build_info_setdefault(libxl__gc *gc,
>          libxl_defbool_setdefault(&b_info->u.hvm.vpt_align,          true);
>          libxl_defbool_setdefault(&b_info->u.hvm.altp2m,             false);
>          libxl_defbool_setdefault(&b_info->u.hvm.usb,                false);
> +        libxl_defbool_setdefault(&b_info->u.hvm.vkb_device,         true);
>          libxl_defbool_setdefault(&b_info->u.hvm.xen_platform_pci,   true);
>  
>          libxl_defbool_setdefault(&b_info->u.hvm.spice.enable, false);
> @@ -1416,9 +1417,11 @@ static void domcreate_launch_dm(libxl__egc *egc, 
> libxl__multidev *multidev,
>          libxl__device_console_add(gc, domid, &console, state, &device);
>          libxl__device_console_dispose(&console);
>  
> -        libxl_device_vkb_init(&vkb);
> -        libxl__device_add(gc, domid, &libxl__vkb_devtype, &vkb);
> -        libxl_device_vkb_dispose(&vkb);
> +        if (libxl_defbool_val(d_config->b_info.u.hvm.vkb_device)) {
> +            libxl_device_vkb_init(&vkb);
> +            libxl__device_add(gc, domid, &libxl__vkb_devtype, &vkb);
> +            libxl_device_vkb_dispose(&vkb);
> +        }
>  
>          dcs->sdss.dm.guest_domid = domid;
>          if (libxl_defbool_val(d_config->b_info.device_model_stubdomain))
> diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
> index b685ac47ac..9a0b92f1d4 100644
> --- a/tools/libxl/libxl_types.idl
> +++ b/tools/libxl/libxl_types.idl
> @@ -583,6 +583,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
>                                         # - "tablet" for absolute mouse,
>                                         # - "mouse" for PS/2 protocol 
> relative mouse
>                                         ("usbdevice",        string),
> +                                       ("vkb_device",       libxl_defbool),
>                                         ("soundhw",          string),
>                                         ("xen_platform_pci", libxl_defbool),
>                                         ("usbdevice_list",   
> libxl_string_list),
> diff --git a/tools/xl/xl_parse.c b/tools/xl/xl_parse.c
> index 352cd214dd..e105bda2bb 100644
> --- a/tools/xl/xl_parse.c
> +++ b/tools/xl/xl_parse.c
> @@ -2652,6 +2652,7 @@ skip_usbdev:
>              fprintf(stderr,"xl: Unable to parse usbdevice.\n");
>              exit(-ERROR_FAIL);
>          }
> +        xlu_cfg_get_defbool(config, "vkb_device", &b_info->u.hvm.vkb_device, 
> 0);
>          xlu_cfg_replace_string (config, "soundhw", &b_info->u.hvm.soundhw, 
> 0);
>          xlu_cfg_get_defbool(config, "xen_platform_pci",
>                              &b_info->u.hvm.xen_platform_pci, 0);

Oh here it is the code which uses the new field -- in that case, you
also need to document this in xl manpage.

The manpage is docs/man/xl.conf.pod.5.

Sorry for not having mentioned this earlier: we also ask for an
accompanying macro for the new field in the public interface. See
various LIBXL_HAVE macros in libxl.h.

Let me know if you have further questions.

Wei.

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