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#include <linux/bug.h>
11#include <linux/limits.h>
12
13#include <asm/cpufeature.h>
14#include <asm/intel_pconfig.h>
15
16#define PCONFIG_CPUID 0x1b
17
18#define PCONFIG_CPUID_SUBLEAF_MASK ((1 << 12) - 1)
19
20/* Subleaf type (EAX) for PCONFIG CPUID leaf (0x1B) */
21enum {
22 PCONFIG_CPUID_SUBLEAF_INVALID = 0,
23 PCONFIG_CPUID_SUBLEAF_TARGETID = 1,
24};
25
26/* Bitmask of supported targets */
27static u64 targets_supported __read_mostly;
28
29int pconfig_target_supported(enum pconfig_target target)
30{
31 /*
32 * We would need to re-think the implementation once we get > 64
33 * PCONFIG targets. Spec allows up to 2^32 targets.
34 */
35 BUILD_BUG_ON(PCONFIG_TARGET_NR >= 64);
36
37 if (WARN_ON_ONCE(target >= 64))
38 return 0;
39 return targets_supported & (1ULL << target);
40}
41
42static int __init intel_pconfig_init(void)
43{
44 int subleaf;
45
46 if (!boot_cpu_has(X86_FEATURE_PCONFIG))
47 return 0;
48
49 /*
50 * Scan subleafs of PCONFIG CPUID leaf.
51 *
52 * Subleafs of the same type need not to be consecutive.
53 *
54 * Stop on the first invalid subleaf type. All subleafs after the first
55 * invalid are invalid too.
56 */
57 for (subleaf = 0; subleaf < INT_MAX; subleaf++) {
58 struct cpuid_regs regs;
59
60 cpuid_count(PCONFIG_CPUID, count: subleaf,
61 eax: &regs.eax, ebx: &regs.ebx, ecx: &regs.ecx, edx: &regs.edx);
62
63 switch (regs.eax & PCONFIG_CPUID_SUBLEAF_MASK) {
64 case PCONFIG_CPUID_SUBLEAF_INVALID:
65 /* Stop on the first invalid subleaf */
66 goto out;
67 case PCONFIG_CPUID_SUBLEAF_TARGETID:
68 /* Mark supported PCONFIG targets */
69 if (regs.ebx < 64)
70 targets_supported |= (1ULL << regs.ebx);
71 if (regs.ecx < 64)
72 targets_supported |= (1ULL << regs.ecx);
73 if (regs.edx < 64)
74 targets_supported |= (1ULL << regs.edx);
75 break;
76 default:
77 /* Unknown CPUID.PCONFIG subleaf: ignore */
78 break;
79 }
80 }
81out:
82 return 0;
83}
84arch_initcall(intel_pconfig_init);
85

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