xref: /openbmc/linux/arch/x86/kernel/cpu/mshyperv.c (revision d0b73b48)
1 /*
2  * HyperV  Detection code.
3  *
4  * Copyright (C) 2010, Novell, Inc.
5  * Author : K. Y. Srinivasan <ksrinivasan@novell.com>
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License as published by
9  * the Free Software Foundation; version 2 of the License.
10  *
11  */
12 
13 #include <linux/types.h>
14 #include <linux/time.h>
15 #include <linux/clocksource.h>
16 #include <linux/module.h>
17 #include <asm/processor.h>
18 #include <asm/hypervisor.h>
19 #include <asm/hyperv.h>
20 #include <asm/mshyperv.h>
21 
22 struct ms_hyperv_info ms_hyperv;
23 EXPORT_SYMBOL_GPL(ms_hyperv);
24 
25 static bool __init ms_hyperv_platform(void)
26 {
27 	u32 eax;
28 	u32 hyp_signature[3];
29 
30 	if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
31 		return false;
32 
33 	cpuid(HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS,
34 	      &eax, &hyp_signature[0], &hyp_signature[1], &hyp_signature[2]);
35 
36 	return eax >= HYPERV_CPUID_MIN &&
37 		eax <= HYPERV_CPUID_MAX &&
38 		!memcmp("Microsoft Hv", hyp_signature, 12);
39 }
40 
41 static cycle_t read_hv_clock(struct clocksource *arg)
42 {
43 	cycle_t current_tick;
44 	/*
45 	 * Read the partition counter to get the current tick count. This count
46 	 * is set to 0 when the partition is created and is incremented in
47 	 * 100 nanosecond units.
48 	 */
49 	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
50 	return current_tick;
51 }
52 
53 static struct clocksource hyperv_cs = {
54 	.name		= "hyperv_clocksource",
55 	.rating		= 400, /* use this when running on Hyperv*/
56 	.read		= read_hv_clock,
57 	.mask		= CLOCKSOURCE_MASK(64),
58 };
59 
60 static void __init ms_hyperv_init_platform(void)
61 {
62 	/*
63 	 * Extract the features and hints
64 	 */
65 	ms_hyperv.features = cpuid_eax(HYPERV_CPUID_FEATURES);
66 	ms_hyperv.hints    = cpuid_eax(HYPERV_CPUID_ENLIGHTMENT_INFO);
67 
68 	printk(KERN_INFO "HyperV: features 0x%x, hints 0x%x\n",
69 	       ms_hyperv.features, ms_hyperv.hints);
70 
71 	clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100);
72 }
73 
74 const __refconst struct hypervisor_x86 x86_hyper_ms_hyperv = {
75 	.name			= "Microsoft HyperV",
76 	.detect			= ms_hyperv_platform,
77 	.init_platform		= ms_hyperv_init_platform,
78 };
79 EXPORT_SYMBOL(x86_hyper_ms_hyperv);
80