1 /*
2 * This file and its contents are supplied under the terms of the
3 * Common Development and Distribution License ("CDDL"), version 1.0.
4 * You may only use this file in accordance with the terms of version
5 * 1.0 of the CDDL.
6 *
7 * A full copy of the text of the CDDL should have accompanied this
8 * source. A copy of the CDDL is also available via the Internet at
9 * http://www.illumos.org/license/CDDL.
10 */
11
12 /*
13 * Copyright 2021 Jason King
14 */
15
16 #include <sys/x86_archext.h>
17 #include <sys/tsc.h>
18
19 /* For VMs, this leaf will contain the largest VM leaf supported in EAX */
20 #define CPUID_VM_LEAF_MAX 0x40000000
21
22 /*
23 * From https://lwn.net/Articles/301888/, CPUID leaf 0x40000010 (when present)
24 * on VMware will contain the TSC frequency in kHz. While it would have been
25 * nice to locate an official bit of documentation from VMware, implementations
26 * in both Linux and FreeBSD agree with the above link, so it seems reasonable
27 * to use it as well.
28 */
29 #define CPUID_VM_LEAF_FREQ 0x40000010
30
31 static boolean_t
tsc_calibrate_vmware(uint64_t * freqp)32 tsc_calibrate_vmware(uint64_t *freqp)
33 {
34 if (get_hwenv() != HW_VMWARE)
35 return (B_FALSE);
36
37 struct cpuid_regs regs = { 0 };
38
39 /* First determine the largest VM leaf supported */
40 regs.cp_eax = CPUID_VM_LEAF_MAX;
41 __cpuid_insn(®s);
42
43 if (regs.cp_eax < CPUID_VM_LEAF_FREQ)
44 return (B_FALSE);
45
46 regs.cp_eax = CPUID_VM_LEAF_FREQ;
47 __cpuid_insn(®s);
48
49 /*
50 * While not observed in the wild, as a precautionary measure,
51 * we treat a value of 0 as a failure out of an excess of caution.
52 */
53 if (regs.cp_eax == 0)
54 return (B_FALSE);
55
56 /* Convert from kHz to Hz */
57 *freqp = (uint64_t)regs.cp_eax * 1000;
58
59 return (B_TRUE);
60 }
61
62 static tsc_calibrate_t tsc_calibration_vmware = {
63 .tscc_source = "VMware",
64 .tscc_preference = 100,
65 .tscc_calibrate = tsc_calibrate_vmware,
66 };
67 TSC_CALIBRATION_SOURCE(tsc_calibration_vmware);
68