Re: [Xen-devel] [PATCH v5 1/6] libxl: do not add a vkb backend to hvm guests

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxx [mailto:xen-devel-
> bounces@xxxxxxxxxxxxx] On Behalf Of Stefano Stabellini
> Sent: 23 July 2015 18:28
> To: xen-devel@xxxxxxxxxxxxxxxxxxx
> Cc: Wei Liu; Ian Jackson; Ian Campbell; Stefano Stabellini
> Subject: [Xen-devel] [PATCH v5 1/6] libxl: do not add a vkb backend to hvm
> guests
> 
> When QEMU restricts its xenstore connection, it cannot provide PV
> backends. A separate QEMU instance is required to provide PV backends in
> userspace, such as qdisk. With two separate instances, it is not
> possible to take advantage of vkb for mouse and keyboard, as the QEMU
> that emulates the graphic card (the device model), would be separate
> from the QEMU running the vkb backend (PV QEMU).
> 
> Removing this functionality is acceptable, because is only useful for
> power saving when usb emulation is off, letting QEMU sleep for longer
> periods of time.  However usb emulation is on by default, and how to
> take advantage of this configuration has never been documented.
> 

I don't think I agree. Turning off USB emulation for HVM guests (particularly 
Windows) has been shown to be highly advantageous in performance and 
scalability terms, and we have a prototype HID driver (not yet part of the 
XenProject driver set, but hopefully soon will be) which uses vkb.

  Paul

> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> ---
>  tools/libxl/libxl_create.c |    5 -----
>  1 file changed, 5 deletions(-)
> 
> diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
> index f0da7dc..a74b340 100644
> --- a/tools/libxl/libxl_create.c
> +++ b/tools/libxl/libxl_create.c
> @@ -1275,17 +1275,12 @@ static void domcreate_launch_dm(libxl__egc
> *egc, libxl__multidev *multidev,
>      {
>          libxl__device_console console;
>          libxl__device device;
> -        libxl_device_vkb vkb;
> 
>          init_console_info(gc, &console, 0);
>          console.backend_domid = state->console_domid;
>          libxl__device_console_add(gc, domid, &console, state, &device);
>          libxl__device_console_dispose(&console);
> 
> -        libxl_device_vkb_init(&vkb);
> -        libxl__device_vkb_add(gc, domid, &vkb);
> -        libxl_device_vkb_dispose(&vkb);
> -
>          dcs->dmss.dm.guest_domid = domid;
>          if (libxl_defbool_val(d_config->b_info.device_model_stubdomain))
>              libxl__spawn_stub_dm(egc, &dcs->dmss);
> --
> 1.7.10.4
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel