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 
xen_setup_features(void)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 }
53