diff mbox series

[14/29] x86/cpu: Add legacy topology parser

Message ID 20230724172844.515260597@linutronix.de
State Superseded
Headers show
Series x86/cpu: Rework the topology evaluation | expand

Commit Message

Thomas Gleixner July 24, 2023, 5:44 p.m. UTC
The legacy topology detection via CPUID leaf 4, which provides the number
of cores in the package and CPUID leaf 1 which provides the number of
logical CPUs in case that FEATURE_HT is enabled and the CMP_LEGACY feature
is not set, is shared for Intel, Centaur amd Zhaoxin CPUs.

Lift the code from common.c without the early detection hack and provide it
as common fallback mechanism.

Will be utilized in later changes.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/kernel/cpu/common.c          |    3 ++
 arch/x86/kernel/cpu/topology.h        |    2 +
 arch/x86/kernel/cpu/topology_common.c |   37 ++++++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+)
diff mbox series

Patch

--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -883,6 +883,9 @@  void detect_ht(struct cpuinfo_x86 *c)
 #ifdef CONFIG_SMP
 	int index_msb, core_bits;
 
+	if (topo_is_converted(c))
+		return;
+
 	if (detect_ht_early(c) < 0)
 		return;
 
--- a/arch/x86/kernel/cpu/topology.h
+++ b/arch/x86/kernel/cpu/topology.h
@@ -7,6 +7,8 @@  struct topo_scan {
 	unsigned int		dom_shifts[TOPO_MAX_DOMAIN];
 	unsigned int		dom_ncpus[TOPO_MAX_DOMAIN];
 
+	// Legacy CPUID[1]:EBX[23:16] number of logical processors
+	unsigned int		ebx1_nproc_shift;
 };
 
 bool topo_is_converted(struct cpuinfo_x86 *c);
--- a/arch/x86/kernel/cpu/topology_common.c
+++ b/arch/x86/kernel/cpu/topology_common.c
@@ -24,6 +24,41 @@  void topology_set_dom(struct topo_scan *
 	}
 }
 
+static unsigned int parse_num_cores(struct cpuinfo_x86 *c)
+{
+	struct {
+		u32	cache_type	:  5,
+			unused		: 21,
+			ncores		:  6;
+	} eax;
+
+	if (c->cpuid_level < 4)
+		return 1;
+
+	cpuid_subleaf_reg(4, 0, CPUID_EAX, &eax);
+	if (!eax.cache_type)
+		return 1;
+
+	return eax.ncores + 1;
+}
+
+static void __maybe_unused parse_legacy(struct topo_scan *tscan)
+{
+	unsigned int cores, core_shift, smt_shift = 0;
+	struct cpuinfo_x86 *c = tscan->c;
+
+	cores = parse_num_cores(c);
+	core_shift = get_count_order(cores);
+
+	if (cpu_has(c, X86_FEATURE_HT)) {
+		if (!WARN_ON_ONCE(tscan->ebx1_nproc_shift < core_shift))
+			smt_shift = tscan->ebx1_nproc_shift - core_shift;
+	}
+
+	topology_set_dom(tscan, TOPO_SMT_DOMAIN, smt_shift, 1U << smt_shift);
+	topology_set_dom(tscan, TOPO_CORE_DOMAIN, core_shift, cores >> smt_shift);
+}
+
 bool topo_is_converted(struct cpuinfo_x86 *c)
 {
 	/* Temporary until everything is converted over. */
@@ -88,6 +123,8 @@  static void parse_topology(struct topo_s
 	/* The above is sufficient for UP */
 	if (!IS_ENABLED(CONFIG_SMP))
 		return;
+
+	tscan->ebx1_nproc_shift = get_count_order(ebx.nproc);
 }
 
 static void topo_set_ids(struct topo_scan *tscan)