Re: [Xen-devel] [PATCH v3 5/7] x86/dom0: Improve dom0= useability

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

On Wed, Jan 16, 2019 at 09:00:48AM +0000, Andrew Cooper wrote:
> Having a pvh boolean isn't ideal.  If we gain a 3rd virtulsation mode,
> what does `dom0=no-pvh` mean?
> 
> Change the syntax to be "dom0 = pv | pvh" which offers an option to more
> obviously select PV mode.  Hide both options behind the relevent
> CONFIG_* settings, and default to PVH mode when CONFIG_PV is compiled
> out.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Wei Liu <wei.liu2@xxxxxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Juergen Gross <jgross@xxxxxxxx>
> 
> This is fine for compatibility purposes, as this option wasn't present
> in Xen 4.11
> 
> v2:
>  * New
> v3:
>  * Use cmdline_strcmp() rather than introducing yet more buggy strncmp()
> ---
>  docs/misc/xen-command-line.pandoc | 16 +++++++++-------
>  xen/arch/x86/dom0_build.c         |  8 +++++---
>  2 files changed, 14 insertions(+), 10 deletions(-)
> 
> diff --git a/docs/misc/xen-command-line.pandoc 
> b/docs/misc/xen-command-line.pandoc
> index 4f27e54..365d2ee 100644
> --- a/docs/misc/xen-command-line.pandoc
> +++ b/docs/misc/xen-command-line.pandoc
> @@ -637,21 +637,23 @@ trace feature is only enabled in debugging builds of 
> Xen.
>  Specify the bit width of the DMA heap.
>  
>  ### dom0
> -    = List of [ pvh=<bool>, shadow=<bool>, verbose=<bool> ]
> +    = List of [ pv | pvh, shadow=<bool>, verbose=<bool> ]
>  
>      Applicability: x86
>  
>  Controls for how dom0 is constructed on x86 systems.
>  
> -*   The `pvh` boolean controls whether dom0 is constructed as a PV or a PVH
> -    guest.  The default is PV.  In addition, the following requirements must
> -    be met:
> +*   The `pv` and `pvh` options select the virtualisation mode of dom0.
> +
> +    The `pv` option is only available when `CONFIG_PV` is compiled in.  The
> +    `pvh` option is only available when `CONFIG_HVM` is compiled in.  When
> +    both options are compiled in, the default is PV.

I would maybe add something along the lines of: "Setting both the `pv`
and the `pvh` options in combination is undefined".

Thanks.

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