linux-kernel - [PATCH v2 08/10] x86/cpufeatures: Add feature bits for AMD heterogeneous processor

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Date: Mon, 13 May 2024 10:07:26 +0800
From: Perry Yuan <perry.yuan@....com>
To: <Mario.Limonciello@....com>, <gautham.shenoy@....com>,
	<Ray.Huang@....com>, <Borislav.Petkov@....com>
CC: <rafael.j.wysocki@...el.com>, <Alexander.Deucher@....com>,
	<Xinmei.Huang@....com>, <Xiaojian.Du@....com>, <Li.Meng@....com>,
	<linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v2 08/10] x86/cpufeatures: Add feature bits for AMD heterogeneous processor

CPUID leaf 0x80000026 advertises core types with different efficiency rankings

Bit 30 indicates the heterogeneous core topology feature, if the bit
set, it means not all instances at the current hierarchical level have
the same core topology.

For better utilization of feature words and help to identify core type,
X86_FEATURE_HETERO_CORE_TOPOLOGY is added as a few scattered feature bits.

Link: https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/programmer-references/24593.pdf
PDF p274
Signed-off-by: Perry Yuan <perry.yuan@....com>
---
 arch/x86/include/asm/cpufeatures.h | 1 +
 arch/x86/kernel/cpu/scattered.c    | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 3c7434329661..39a92338c015 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -470,6 +470,7 @@
 #define X86_FEATURE_BHI_CTRL		(21*32+ 2) /* "" BHI_DIS_S HW control available */
 #define X86_FEATURE_CLEAR_BHB_HW	(21*32+ 3) /* "" BHI_DIS_S HW control enabled */
 #define X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT (21*32+ 4) /* "" Clear branch history at vmexit using SW loop */
+#define X86_FEATURE_HETERO_CORE_TOPOLOGY       (21*32+ 5) /* "" Heterogeneous Core Topology */
 
 /*
  * BUG word(s)
diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
index af5aa2c754c2..9e237a3daf7e 100644
--- a/arch/x86/kernel/cpu/scattered.c
+++ b/arch/x86/kernel/cpu/scattered.c
@@ -51,6 +51,7 @@ static const struct cpuid_bit cpuid_bits[] = {
 	{ X86_FEATURE_PERFMON_V2,	CPUID_EAX,  0, 0x80000022, 0 },
 	{ X86_FEATURE_AMD_LBR_V2,	CPUID_EAX,  1, 0x80000022, 0 },
 	{ X86_FEATURE_AMD_LBR_PMC_FREEZE,	CPUID_EAX,  2, 0x80000022, 0 },
+	{ X86_FEATURE_HETERO_CORE_TOPOLOGY,	CPUID_EAX,  30, 0x80000026, 0 },
 	{ 0, 0, 0, 0, 0 }
 };
 
-- 
2.34.1