linux-kernel - [PATCH 4/4] x86/topology: Set cpu_die_id only if DIE

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Date:   Mon,  9 Nov 2020 21:06:59 +0000
From:   Yazen Ghannam <Yazen.Ghannam@....com>
To:     x86@...nel.org
Cc:     Yazen Ghannam <Yazen.Ghannam@....com>,
        linux-kernel@...r.kernel.org,
        Smita.KoralahalliChannabasappa@....com, linux-edac@...r.kernel.org,
        puwen@...on.cn, kim.phillips@....com, thomas.lendacky@....com,
        wei.huang2@....com
Subject: [PATCH 4/4] x86/topology: Set cpu_die_id only if DIE_TYPE found

From: Yazen Ghannam <yazen.ghannam@....com>

CPUID Leaf 0x1F defines a DIE_TYPE level, but CPUID Leaf 0xB does not.
However, detect_extended_topology() will set struct
cpuinfo_x86.cpu_die_id regardless of whether a valid Die ID was found.

Only set cpu_die_id if a DIE_TYPE level is found. CPU topology code may
use another value for cpu_die_id, e.g. the AMD NodeId on AMD-based
systems. Code ordering should be maintained so that the CPUID Leaf 0x1F
Die ID value will take precedence on systems that may use another value.

Suggested-by: Borislav Petkov <bp@...en8.de>
Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
---
 arch/x86/kernel/cpu/topology.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c
index d3a0791bc052..1068002c8532 100644
--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -96,6 +96,7 @@ int detect_extended_topology(struct cpuinfo_x86 *c)
 	unsigned int ht_mask_width, core_plus_mask_width, die_plus_mask_width;
 	unsigned int core_select_mask, core_level_siblings;
 	unsigned int die_select_mask, die_level_siblings;
+	bool die_level_present = false;
 	int leaf;
 
 	leaf = detect_extended_topology_leaf(c);
@@ -126,6 +127,7 @@ int detect_extended_topology(struct cpuinfo_x86 *c)
 			die_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
 		}
 		if (LEAFB_SUBTYPE(ecx) == DIE_TYPE) {
+			die_level_present = true;
 			die_level_siblings = LEVEL_MAX_SIBLINGS(ebx);
 			die_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
 		}
@@ -139,8 +141,12 @@ int detect_extended_topology(struct cpuinfo_x86 *c)
 
 	c->cpu_core_id = apic->phys_pkg_id(c->initial_apicid,
 				ht_mask_width) & core_select_mask;
-	c->cpu_die_id = apic->phys_pkg_id(c->initial_apicid,
-				core_plus_mask_width) & die_select_mask;
+
+	if (die_level_present) {
+		c->cpu_die_id = apic->phys_pkg_id(c->initial_apicid,
+					core_plus_mask_width) & die_select_mask;
+	}
+
 	c->phys_proc_id = apic->phys_pkg_id(c->initial_apicid,
 				die_plus_mask_width);
 	/*
-- 
2.25.1