[PATCHv2 4/5] x86/pconfig: Detect PCONFIG targets

[Kirill A. Shutemov]

Intel PCONFIG targets are enumerated via new CPUID leaf 0x1b. This patch
detects all supported targets of PCONFIG and implements helper to check
if the target is supported.

Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
---
 arch/x86/include/asm/intel_pconfig.h | 15 +++++++
 arch/x86/kernel/cpu/Makefile         |  2 +-
 arch/x86/kernel/cpu/intel_pconfig.c  | 82 ++++++++++++++++++++++++++++++++++++
 3 files changed, 98 insertions(+), 1 deletion(-)
 create mode 100644 arch/x86/include/asm/intel_pconfig.h
 create mode 100644 arch/x86/kernel/cpu/intel_pconfig.c

diff --git a/arch/x86/include/asm/intel_pconfig.h 
b/arch/x86/include/asm/intel_pconfig.h
new file mode 100644
index 000000000000..fb7a37c3798b
--- /dev/null
+++ b/arch/x86/include/asm/intel_pconfig.h
@@ -0,0 +1,15 @@
+#ifndef        _ASM_X86_INTEL_PCONFIG_H
+#define        _ASM_X86_INTEL_PCONFIG_H
+
+#include <asm/asm.h>
+#include <asm/processor.h>
+
+enum pconfig_target {
+       INVALID_TARGET  = 0,
+       MKTME_TARGET    = 1,
+       PCONFIG_TARGET_NR
+};
+
+int pconfig_target_supported(enum pconfig_target target);
+
+#endif /* _ASM_X86_INTEL_PCONFIG_H */
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index 570e8bb1f386..a66229f51b12 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -28,7 +28,7 @@ obj-y                 += cpuid-deps.o
 obj-$(CONFIG_PROC_FS)  += proc.o
 obj-$(CONFIG_X86_FEATURE_NAMES) += capflags.o powerflags.o
 
-obj-$(CONFIG_CPU_SUP_INTEL)            += intel.o
+obj-$(CONFIG_CPU_SUP_INTEL)            += intel.o intel_pconfig.o
 obj-$(CONFIG_CPU_SUP_AMD)              += amd.o
 obj-$(CONFIG_CPU_SUP_CYRIX_32)         += cyrix.o
 obj-$(CONFIG_CPU_SUP_CENTAUR)          += centaur.o
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.shute...@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);
-- 
2.15.1