Re: [PATCH 1/3] xen: check required Xen features

[Boris Ostrovsky]

On 4/22/21 11:10 AM, Juergen Gross wrote:
>  
> +/*
> + * Linux kernel expects at least Xen 4.0.
> + *
> + * Assume some features to be available for that reason (depending on guest
> + * mode, of course).
> + */
> +#define chk_feature(f) {                                             \
> +             if (!xen_feature(f))                                    \
> +                     pr_err("Xen: feature %s not available!\n", #f); \
> +     }


With your changes in the subsequent patches, are we still going to function 
properly without those features? (i.e. maybe we should just panic)


(Also, chk_required_features() perhaps?)


-boris


> +
>  u8 xen_features[XENFEAT_NR_SUBMAPS * 32] __read_mostly;
>  EXPORT_SYMBOL_GPL(xen_features);
>  
> @@ -31,4 +44,9 @@ void xen_setup_features(void)
>               for (j = 0; j < 32; j++)
>                       xen_features[i * 32 + j] = !!(fi.submap & 1<<j);
>       }
> +
> +     if (xen_pv_domain()) {
> +             chk_feature(XENFEAT_mmu_pt_update_preserve_ad);
> +             chk_feature(XENFEAT_gnttab_map_avail_bits);
> +     }
>  }