Re: [Xen-devel] [PATCH] xl: Add 'pvh' config option

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Mar 30, 2017 at 07:06:15PM -0400, Boris Ostrovsky wrote:
> In addition to 'device_model_version="none"' config option users can
> also use 'pvh=1' in xl configuration file when creating a PVH guest.

I'm not sure, but I think the plan was to remove device_model_version="none"
and instead just use pvh=1, instead of keeping both. I don't have a strong
opinion here, so I will leave that to the xl maintainers.

I'm also not sure, but if you use device_model_version="none" can you use QDISK
for PVH disk backend? (and pygrub).

> We can skip parsing options related to device model once we establish
> that we are building PVH guest.
> 
> Also process 'device_model_version="none"' for HVM guests only since
> it is not a valid model for PV guests.
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> ---
>  docs/man/xl.cfg.pod.5.in |  7 ++++++-
>  tools/xl/xl_parse.c      | 12 +++++++++++-
>  2 files changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/docs/man/xl.cfg.pod.5.in b/docs/man/xl.cfg.pod.5.in
> index 206d33e..5833987 100644
> --- a/docs/man/xl.cfg.pod.5.in
> +++ b/docs/man/xl.cfg.pod.5.in
> @@ -1201,6 +1201,11 @@ expose unexpected bugs in the guest, or find bugs in 
> Xen, so it is
>  possible to disable this feature.  Use of out of sync page tables,
>  when Xen thinks it appropriate, is the default.
>  
> +=item B<pvh=BOOLEAN>
> +
> +Don't use any device model. This requires a kernel capable of booting
> +without emulated devices. Default is 0.
> +
>  =item B<shadow_memory=MBYTES>
>  
>  Number of megabytes to set aside for shadowing guest pagetable pages
> @@ -1966,7 +1971,7 @@ This device-model is still the default for NetBSD dom0.
>  =item B<none>
>  
>  Don't use any device model. This requires a kernel capable of booting
> -without emulated devices.
> +without emulated devices. This is a synonym for L</"pvh"> option above.
>  
>  =back
>  
> diff --git a/tools/xl/xl_parse.c b/tools/xl/xl_parse.c
> index 66327dc..aa591cd 100644
> --- a/tools/xl/xl_parse.c
> +++ b/tools/xl/xl_parse.c
> @@ -1817,6 +1817,12 @@ skip_usbdev:
>          break;
>      }
>  
> +    if (c_info->type == LIBXL_DOMAIN_TYPE_HVM &&

Hm, this will mean that the user needs to specify:

builder="hvm"
pvh=1

Or else the option is not going to be parsed.

> +        !xlu_cfg_get_long(config, "pvh", &l, 0) && l) {
> +        b_info->device_model_version = LIBXL_DEVICE_MODEL_VERSION_NONE;
> +        goto skip_device_model;
> +    }
> +

Roger.

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