[PATCHv3 4/5] x86/pconfig: Detect PCONFIG targets

From: Kirill A. Shutemov
Date: Fri Feb 09 2018 - 09:08:31 EST


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.shutemov@xxxxxxxxxxxxxxx>
---
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.shutemov@xxxxxxxxxxxxxxx>
+ */
+
+#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