drivers/xen/features.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /******************************************************************************
0003  * features.c
0004  *
0005  * Xen feature flags.
0006  *
0007  * Copyright (c) 2006, Ian Campbell, XenSource Inc.
0008  */
0009 #include <linux/types.h>
0010 #include <linux/cache.h>
0011 #include <linux/export.h>
0012 #include <linux/printk.h>
0013
0014 #include <asm/xen/hypercall.h>
0015
0016 #include <xen/xen.h>
0017 #include <xen/interface/xen.h>
0018 #include <xen/interface/version.h>
0019 #include <xen/features.h>
0020
0021 /*
0022  * Linux kernel expects at least Xen 4.0.
0023  *
0024  * Assume some features to be available for that reason (depending on guest
0025  * mode, of course).
0026  */
0027 #define chk_required_feature(f) {                   \
0028         if (!xen_feature(f))                    \
0029             panic("Xen: feature %s not available!\n", #f);  \
0030     }
0031
0032 u8 xen_features[XENFEAT_NR_SUBMAPS * 32] __read_mostly;
0033 EXPORT_SYMBOL_GPL(xen_features);
0034
0035 void xen_setup_features(void)
0036 {
0037     struct xen_feature_info fi;
0038     int i, j;
0039
0040     for (i = 0; i < XENFEAT_NR_SUBMAPS; i++) {
0041         fi.submap_idx = i;
0042         if (HYPERVISOR_xen_version(XENVER_get_features, &fi) < 0)
0043             break;
0044         for (j = 0; j < 32; j++)
0045             xen_features[i * 32 + j] = !!(fi.submap & 1U << j);
0046     }
0047
0048     if (xen_pv_domain()) {
0049         chk_required_feature(XENFEAT_mmu_pt_update_preserve_ad);
0050         chk_required_feature(XENFEAT_gnttab_map_avail_bits);
0051     }
0052 }