drivers/xen/features.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /******************************************************************************
   3  * features.c
   4  *
   5  * Xen feature flags.
   6  *
   7  * Copyright (c) 2006, Ian Campbell, XenSource Inc.
   8  */
   9 #include <linux/types.h>
  10 #include <linux/cache.h>
  11 #include <linux/export.h>
  12 #include <linux/printk.h>
  13
  14 #include <asm/xen/hypercall.h>
  15
  16 #include <xen/xen.h>
  17 #include <xen/interface/xen.h>
  18 #include <xen/interface/version.h>
  19 #include <xen/features.h>
  20
  21 /*
  22  * Linux kernel expects at least Xen 4.0.
  23  *
  24  * Assume some features to be available for that reason (depending on guest
  25  * mode, of course).
  26  */
  27 #define chk_required_feature(f) {                                       \
  28                 if (!xen_feature(f))                                    \
  29                         panic("Xen: feature %s not available!\n", #f);  \
  30         }
  31
  32 u8 xen_features[XENFEAT_NR_SUBMAPS * 32] __read_mostly;
  33 EXPORT_SYMBOL_GPL(xen_features);
  34
  35 void xen_setup_features(void)
  36 {
  37         struct xen_feature_info fi;
  38         int i, j;
  39
  40         for (i = 0; i < XENFEAT_NR_SUBMAPS; i++) {
  41                 fi.submap_idx = i;
  42                 if (HYPERVISOR_xen_version(XENVER_get_features, &fi) < 0)
  43                         break;
  44                 for (j = 0; j < 32; j++)
  45                         xen_features[i * 32 + j] = !!(fi.submap & 1U << j);
  46         }
  47
  48         if (xen_pv_domain()) {
  49                 chk_required_feature(XENFEAT_mmu_pt_update_preserve_ad);
  50                 chk_required_feature(XENFEAT_gnttab_map_avail_bits);
  51         }
  52 }