arch/x86/kernel/cpu/intel_pconfig.c

   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);