Re: [Xen-devel] [PATCH 6/6] xen/public: Obsolete HVM_PARAM_PAE_ENABLED

[Jan Beulich <jbeulich@suse.com>]

On 05.02.2020 17:50, Andrew Cooper wrote:
> --- a/tools/libxc/xc_sr_restore_x86_hvm.c
> +++ b/tools/libxc/xc_sr_restore_x86_hvm.c
> @@ -72,6 +72,16 @@ static int handle_hvm_params(struct xc_sr_context *ctx,
>          case HVM_PARAM_BUFIOREQ_PFN:
>              xc_clear_domain_page(xch, ctx->domid, entry->value);
>              break;
> +
> +        case HVM_PARAM_PAE_ENABLED:
> +            /*
> +             * This HVM_PARAM only ever existed a non-standard calling ABI for
> +             * xc_cpuid_apply_policy().  It has now been updated to use a
> +             * regular calling convention, making the param obsolete.
> +             *
> +             * Discard if we find it in an old migration stream.
> +             */
> +            continue;

Having also looked at the previous patch (the only one in this series
relevant to the adjustments done here afaict) I wonder whether simply
ignoring it (i.e. not even warning anywhere when out of sync with
whatever info->u.hvm.pae gets populated from) is a good approach. But
of course I may be easily missing aspects here that make this quite
fine.

> --- a/xen/include/public/hvm/params.h
> +++ b/xen/include/public/hvm/params.h
> @@ -86,7 +86,7 @@
>  #define HVM_PARAM_STORE_PFN    1
>  #define HVM_PARAM_STORE_EVTCHN 2
>  
> -#define HVM_PARAM_PAE_ENABLED  4
> +#define HVM_PARAM_PAE_ENABLED  4 /* Obsolete.  Do not use. */

I think this should be moved up in the deprecated section. With this
hypervisor parts
Reviewed-by: Jan Beulich <jbeulich@suse.com>

As an aside I also think that section should check for just __XEN__,
not also __XEN_TOOLS__.

Jan

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