1 files changed, 82 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/intel_pconfig.c b/arch/x86/kernel/cpu/intel_pconfig.c
new file mode 100644
index 000000000000..0771a905b286
--- /dev/null
+++ b/arch/x86/kernel/cpu/intel_pconfig.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Intel PCONFIG instruction support.
+ *
+ * Copyright (C) 2017 Intel Corporation
+ *
+ * Author:
+ *      Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
+ */
+
+#include <asm/cpufeature.h>
+#include <asm/intel_pconfig.h>
+
+#define PCONFIG_CPUID                   0x1b
+
+#define PCONFIG_CPUID_SUBLEAF_MASK      ((1 << 12) - 1)
+
+/* Subleaf type (EAX) for PCONFIG CPUID leaf (0x1B) */
+enum {
+        PCONFIG_CPUID_SUBLEAF_INVALID   = 0,
+        PCONFIG_CPUID_SUBLEAF_TARGETID  = 1,
+};
+
+/* Bitmask of supported targets */
+static u64 targets_supported __read_mostly;
+
+int pconfig_target_supported(enum pconfig_target target)
+{
+        /*
+         * We would need to re-think the implementation once we get > 64
+         * PCONFIG targets. Spec allows up to 2^32 targets.
+         */
+        BUILD_BUG_ON(PCONFIG_TARGET_NR >= 64);
+
+        if (WARN_ON_ONCE(target >= 64))
+                return 0;
+        return targets_supported & (1ULL << target);
+}
+
+static int __init intel_pconfig_init(void)
+{
+        int subleaf;
+
+        if (!boot_cpu_has(X86_FEATURE_PCONFIG))
+                return 0;
+
+        /*
+         * Scan subleafs of PCONFIG CPUID leaf.
+         *
+         * Subleafs of the same type need not to be consecutive.
+         *
+         * Stop on the first invalid subleaf type. All subleafs after the first
+         * invalid are invalid too.
+         */
+        for (subleaf = 0; subleaf < INT_MAX; subleaf++) {
+                struct cpuid_regs regs;
+
+                cpuid_count(PCONFIG_CPUID, subleaf,
+                                &regs.eax, &regs.ebx, &regs.ecx, &regs.edx);
+
+                switch (regs.eax & PCONFIG_CPUID_SUBLEAF_MASK) {
+                case PCONFIG_CPUID_SUBLEAF_INVALID:
+                        /* Stop on the first invalid subleaf */
+                        goto out;
+                case PCONFIG_CPUID_SUBLEAF_TARGETID:
+                        /* Mark supported PCONFIG targets */
+                        if (regs.ebx < 64)
+                                targets_supported |= (1ULL << regs.ebx);
+                        if (regs.ecx < 64)
+                                targets_supported |= (1ULL << regs.ecx);
+                        if (regs.edx < 64)
+                                targets_supported |= (1ULL << regs.edx);
+                        break;
+                default:
+                        /* Unknown CPUID.PCONFIG subleaf: ignore */
+                        break;
+                }
+        }
+out:
+        return 0;
+}
+arch_initcall(intel_pconfig_init);