1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Intel PCONFIG instruction support.
4 *
5 * Copyright (C) 2017 Intel Corporation
6 *
7 * Author:
8 * Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
9 */
10
11#include <asm/cpufeature.h>
12#include <asm/intel_pconfig.h>
13
14#define PCONFIG_CPUID 0x1b
15
16#define PCONFIG_CPUID_SUBLEAF_MASK ((1 << 12) - 1)
17
18/* Subleaf type (EAX) for PCONFIG CPUID leaf (0x1B) */
19enum {
20 PCONFIG_CPUID_SUBLEAF_INVALID = 0,
21 PCONFIG_CPUID_SUBLEAF_TARGETID = 1,
22};
23
24/* Bitmask of supported targets */
25static u64 targets_supported __read_mostly;
26
27int pconfig_target_supported(enum pconfig_target target)
28{
29 /*
30 * We would need to re-think the implementation once we get > 64
31 * PCONFIG targets. Spec allows up to 2^32 targets.
32 */
33 BUILD_BUG_ON(PCONFIG_TARGET_NR >= 64);
34
35 if (WARN_ON_ONCE(target >= 64))
36 return 0;
37 return targets_supported & (1ULL << target);
38}
39
40static int __init intel_pconfig_init(void)
41{
42 int subleaf;
43
44 if (!boot_cpu_has(X86_FEATURE_PCONFIG))
45 return 0;
46
47 /*
48 * Scan subleafs of PCONFIG CPUID leaf.
49 *
50 * Subleafs of the same type need not to be consecutive.
51 *
52 * Stop on the first invalid subleaf type. All subleafs after the first
53 * invalid are invalid too.
54 */
55 for (subleaf = 0; subleaf < INT_MAX; subleaf++) {
56 struct cpuid_regs regs;
57
58 cpuid_count(PCONFIG_CPUID, count: subleaf,
59 eax: &regs.eax, ebx: &regs.ebx, ecx: &regs.ecx, edx: &regs.edx);
60
61 switch (regs.eax & PCONFIG_CPUID_SUBLEAF_MASK) {
62 case PCONFIG_CPUID_SUBLEAF_INVALID:
63 /* Stop on the first invalid subleaf */
64 goto out;
65 case PCONFIG_CPUID_SUBLEAF_TARGETID:
66 /* Mark supported PCONFIG targets */
67 if (regs.ebx < 64)
68 targets_supported |= (1ULL << regs.ebx);
69 if (regs.ecx < 64)
70 targets_supported |= (1ULL << regs.ecx);
71 if (regs.edx < 64)
72 targets_supported |= (1ULL << regs.edx);
73 break;
74 default:
75 /* Unknown CPUID.PCONFIG subleaf: ignore */
76 break;
77 }
78 }
79out:
80 return 0;
81}
82arch_initcall(intel_pconfig_init);
83

source code of linux/arch/x86/kernel/cpu/intel_pconfig.c