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) */
19 enum {
20 	PCONFIG_CPUID_SUBLEAF_INVALID	= 0,
21 	PCONFIG_CPUID_SUBLEAF_TARGETID	= 1,
22 };
23 
24 /* Bitmask of supported targets */
25 static u64 targets_supported __read_mostly;
26 
27 int 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 
40 static 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, subleaf,
59 				&regs.eax, &regs.ebx, &regs.ecx, &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 	}
79 out:
80 	return 0;
81 }
82 arch_initcall(intel_pconfig_init);
83