kernel/cpu/intel_pconfig.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Intel PCONFIG instruction support.
0004  *
0005  * Copyright (C) 2017 Intel Corporation
0006  *
0007  * Author:
0008  *  Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
0009  */
0010
0011 #include <asm/cpufeature.h>
0012 #include <asm/intel_pconfig.h>
0013
0014 #define PCONFIG_CPUID           0x1b
0015
0016 #define PCONFIG_CPUID_SUBLEAF_MASK  ((1 << 12) - 1)
0017
0018 /* Subleaf type (EAX) for PCONFIG CPUID leaf (0x1B) */
0019 enum {
0020     PCONFIG_CPUID_SUBLEAF_INVALID   = 0,
0021     PCONFIG_CPUID_SUBLEAF_TARGETID  = 1,
0022 };
0023
0024 /* Bitmask of supported targets */
0025 static u64 targets_supported __read_mostly;
0026
0027 int pconfig_target_supported(enum pconfig_target target)
0028 {
0029     /*
0030      * We would need to re-think the implementation once we get > 64
0031      * PCONFIG targets. Spec allows up to 2^32 targets.
0032      */
0033     BUILD_BUG_ON(PCONFIG_TARGET_NR >= 64);
0034
0035     if (WARN_ON_ONCE(target >= 64))
0036         return 0;
0037     return targets_supported & (1ULL << target);
0038 }
0039
0040 static int __init intel_pconfig_init(void)
0041 {
0042     int subleaf;
0043
0044     if (!boot_cpu_has(X86_FEATURE_PCONFIG))
0045         return 0;
0046
0047     /*
0048      * Scan subleafs of PCONFIG CPUID leaf.
0049      *
0050      * Subleafs of the same type need not to be consecutive.
0051      *
0052      * Stop on the first invalid subleaf type. All subleafs after the first
0053      * invalid are invalid too.
0054      */
0055     for (subleaf = 0; subleaf < INT_MAX; subleaf++) {
0056         struct cpuid_regs regs;
0057
0058         cpuid_count(PCONFIG_CPUID, subleaf,
0059                 &regs.eax, &regs.ebx, &regs.ecx, &regs.edx);
0060
0061         switch (regs.eax & PCONFIG_CPUID_SUBLEAF_MASK) {
0062         case PCONFIG_CPUID_SUBLEAF_INVALID:
0063             /* Stop on the first invalid subleaf */
0064             goto out;
0065         case PCONFIG_CPUID_SUBLEAF_TARGETID:
0066             /* Mark supported PCONFIG targets */
0067             if (regs.ebx < 64)
0068                 targets_supported |= (1ULL << regs.ebx);
0069             if (regs.ecx < 64)
0070                 targets_supported |= (1ULL << regs.ecx);
0071             if (regs.edx < 64)
0072                 targets_supported |= (1ULL << regs.edx);
0073             break;
0074         default:
0075             /* Unknown CPUID.PCONFIG subleaf: ignore */
0076             break;
0077         }
0078     }
0079 out:
0080     return 0;
0081 }
0082 arch_initcall(intel_pconfig_init);