Re: [PATCH 16/21] libs/guest: make a cpu policy compatible with older Xen versions

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 23/03/2021 09:58, Roger Pau Monne wrote:
> Older Xen versions used to expose some CPUID bits which are no longer
> exposed by default. In order to keep a compatible behavior with
> guests migrated from versions of Xen that don't encode the CPUID data
> on the migration stream introduce a function that sets the same bits
> as older Xen versions.
>
> This is pulled out from xc_cpuid_apply_policy which already has this
> logic present.
>
> No functional change intended.
>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
>  tools/include/xenctrl.h         |  4 ++++
>  tools/libs/guest/xg_cpuid_x86.c | 39 ++++++++++++++++++++++++++++-----
>  2 files changed, 37 insertions(+), 6 deletions(-)
>
> diff --git a/tools/include/xenctrl.h b/tools/include/xenctrl.h
> index 5f3e5e17e9d..6f7158156fa 100644
> --- a/tools/include/xenctrl.h
> +++ b/tools/include/xenctrl.h
> @@ -2627,6 +2627,10 @@ int xc_cpu_policy_calc_compatible(xc_interface *xch,
>                                    const xc_cpu_policy_t p2,
>                                    xc_cpu_policy_t out);
>  
> +/* Make a policy compatible with previous Xen versions. */
> +int xc_cpu_policy_make_compatible(xc_interface *xch, xc_cpu_policy_t policy,
> +                                  bool hvm);

I think this probably wants  "pre-4.14(?)" somewhere obvious, because
"compatible" on its own is very ambiguous.

~Andrew