linux-kernel - [PATCH v5 2/4] x86/cpu/topology: Check for X86_FEATURE_XTOPOLOGY instead of passing has

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Message-ID: <20250901170418.4314-3-kprateek.nayak@amd.com>
Date: Mon, 1 Sep 2025 17:04:16 +0000
From: K Prateek Nayak <kprateek.nayak@....com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
	Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>,
	Jonathan Corbet <corbet@....net>, <x86@...nel.org>
CC: Naveen rao <naveen.rao@....com>, Sairaj Kodilkar <sarunkod@....com>, "H.
 Peter Anvin" <hpa@...or.com>, "Peter Zijlstra (Intel)"
	<peterz@...radead.org>, "Xin Li (Intel)" <xin@...or.com>, Pawan Gupta
	<pawan.kumar.gupta@...ux.intel.com>, <linux-kernel@...r.kernel.org>,
	<kvm@...r.kernel.org>, Mario Limonciello <mario.limonciello@....com>,
	"Gautham R. Shenoy" <gautham.shenoy@....com>, Babu Moger
	<babu.moger@....com>, Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
	K Prateek Nayak <kprateek.nayak@....com>
Subject: [PATCH v5 2/4] x86/cpu/topology: Check for X86_FEATURE_XTOPOLOGY instead of passing has_xtopology

cpu_parse_topology_ext() sets X86_FEATURE_XTOPOLOGY before returning
true if any of the XTOPOLOGY leaf (0x80000026 / 0xb) could be parsed
successfully.

Instead of storing and passing around this return value using
"has_xtopology" in parse_topology_amd(), check for X86_FEATURE_XTOPOLOGY
directly in parse_8000_001e() to simplify the flow.

No functional changes intended.

Signed-off-by: K Prateek Nayak <kprateek.nayak@....com>
---
Changelog v4..v5:

o No functional changes. The diff is slightly altered as a result of
  modifying the comment in parse_topology_amd() in Patch 1.
---
 arch/x86/kernel/cpu/topology_amd.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/cpu/topology_amd.c b/arch/x86/kernel/cpu/topology_amd.c
index c79ebbb639cb..7ebd4a15c561 100644
--- a/arch/x86/kernel/cpu/topology_amd.c
+++ b/arch/x86/kernel/cpu/topology_amd.c
@@ -59,7 +59,7 @@ static void store_node(struct topo_scan *tscan, u16 nr_nodes, u16 node_id)
 	tscan->amd_node_id = node_id;
 }
 
-static bool parse_8000_001e(struct topo_scan *tscan, bool has_topoext)
+static bool parse_8000_001e(struct topo_scan *tscan)
 {
 	struct {
 		// eax
@@ -85,7 +85,7 @@ static bool parse_8000_001e(struct topo_scan *tscan, bool has_topoext)
 	 * If leaf 0xb/0x26 is available, then the APIC ID and the domain
 	 * shifts are set already.
 	 */
-	if (!has_topoext) {
+	if (!cpu_feature_enabled(X86_FEATURE_XTOPOLOGY)) {
 		tscan->c->topo.initial_apicid = leaf.ext_apic_id;
 
 		/*
@@ -175,30 +175,27 @@ static void topoext_fixup(struct topo_scan *tscan)
 
 static void parse_topology_amd(struct topo_scan *tscan)
 {
+	if (cpu_feature_enabled(X86_FEATURE_AMD_HTR_CORES))
+		tscan->c->topo.cpu_type = cpuid_ebx(0x80000026);
+
 	/*
 	 * Try to get SMT, CORE, TILE, and DIE shifts from extended
 	 * CPUID leaf 0x8000_0026 on supported processors first. If
 	 * extended CPUID leaf 0x8000_0026 is not supported, try to
 	 * get SMT and CORE shift from leaf 0xb. If either leaf is
 	 * available, cpu_parse_topology_ext() will return true.
-	 */
-	bool has_xtopology = cpu_parse_topology_ext(tscan);
-
-	if (cpu_feature_enabled(X86_FEATURE_AMD_HTR_CORES))
-		tscan->c->topo.cpu_type = cpuid_ebx(0x80000026);
-
-	/*
+	 *
 	 * If XTOPOLOGY leaves (0x26/0xb) are not available, try to
 	 * get the CORE shift from leaf 0x8000_0008 first.
 	 */
-	if (!has_xtopology && !parse_8000_0008(tscan))
+	if (!cpu_parse_topology_ext(tscan) && !parse_8000_0008(tscan))
 		return;
 
 	/*
 	 * Prefer leaf 0x8000001e if available to get the SMT shift and
 	 * the initial APIC ID if XTOPOLOGY leaves are not available.
 	 */
-	if (parse_8000_001e(tscan, has_xtopology))
+	if (parse_8000_001e(tscan))
 		return;
 
 	/* Try the NODEID MSR */
-- 
2.34.1