x86/cpu: Add CPU type to struct cpuinfo_topology

Sometimes it is required to take actions based on if a CPU is a performance or
efficiency core. As an example, intel_pstate driver uses the Intel core-type
to determine CPU scaling. Also, some CPU vulnerabilities only affect
a specific CPU type, like RFDS only affects Intel Atom. Hybrid systems that
have variants P+E, P-only(Core) and E-only(Atom), it is not straightforward to
identify which variant is affected by a type specific vulnerability.

Such processors do have CPUID field that can uniquely identify them. Like,
P+E, P-only and E-only enumerates CPUID.1A.CORE_TYPE identification, while P+E
additionally enumerates CPUID.7.HYBRID. Based on this information, it is
possible for boot CPU to identify if a system has mixed CPU types.

Add a new field hw_cpu_type to struct cpuinfo_topology that stores the
hardware specific CPU type. This saves the overhead of IPIs to get the CPU
type of a different CPU. CPU type is populated early in the boot process,
before vulnerabilities are enumerated.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Co-developed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/r/20241025171459.1093-5-mario.limonciello@amd.com

3 files changed, 38 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/debugfs.c b/arch/x86/kernel/cpu/debugfs.c
index 3baf3e435834..10719aba6276 100644
--- a/arch/x86/kernel/cpu/debugfs.c
+++ b/arch/x86/kernel/cpu/debugfs.c
@@ -22,6 +22,7 @@ static int cpu_debug_show(struct seq_file *m, void *p)
 	seq_printf(m, "die_id:              %u\n", c->topo.die_id);
 	seq_printf(m, "cu_id:               %u\n", c->topo.cu_id);
 	seq_printf(m, "core_id:             %u\n", c->topo.core_id);
+	seq_printf(m, "cpu_type:            %s\n", get_topology_cpu_type_name(c));
 	seq_printf(m, "logical_pkg_id:      %u\n", c->topo.logical_pkg_id);
 	seq_printf(m, "logical_die_id:      %u\n", c->topo.logical_die_id);
 	seq_printf(m, "llc_id:              %u\n", c->topo.llc_id);
diff --git a/arch/x86/kernel/cpu/topology_amd.c b/arch/x86/kernel/cpu/topology_amd.c
index 7d476fa697ca..03b3c9c3a45e 100644
--- a/arch/x86/kernel/cpu/topology_amd.c
+++ b/arch/x86/kernel/cpu/topology_amd.c
@@ -182,6 +182,9 @@ static void parse_topology_amd(struct topo_scan *tscan)
 	if (cpu_feature_enabled(X86_FEATURE_TOPOEXT))
 		has_topoext = cpu_parse_topology_ext(tscan);
 
+	if (cpu_feature_enabled(X86_FEATURE_AMD_HETEROGENEOUS_CORES))
+		tscan->c->topo.cpu_type = cpuid_ebx(0x80000026);
+
 	if (!has_topoext && !parse_8000_0008(tscan))
 		return;
 
diff --git a/arch/x86/kernel/cpu/topology_common.c b/arch/x86/kernel/cpu/topology_common.c
index 9a6069e7133c..8277c64f88db 100644
--- a/arch/x86/kernel/cpu/topology_common.c
+++ b/arch/x86/kernel/cpu/topology_common.c
@@ -3,6 +3,7 @@
 
 #include <xen/xen.h>
 
+#include <asm/intel-family.h>
 #include <asm/apic.h>
 #include <asm/processor.h>
 #include <asm/smp.h>
@@ -27,6 +28,36 @@ void topology_set_dom(struct topo_scan *tscan, enum x86_topology_domains dom,
 	}
 }
 
+enum x86_topology_cpu_type get_topology_cpu_type(struct cpuinfo_x86 *c)
+{
+	if (c->x86_vendor == X86_VENDOR_INTEL) {
+		switch (c->topo.intel_type) {
+		case INTEL_CPU_TYPE_ATOM: return TOPO_CPU_TYPE_EFFICIENCY;
+		case INTEL_CPU_TYPE_CORE: return TOPO_CPU_TYPE_PERFORMANCE;
+		}
+	}
+	if (c->x86_vendor == X86_VENDOR_AMD) {
+		switch (c->topo.amd_type) {
+		case 0:	return TOPO_CPU_TYPE_PERFORMANCE;
+		case 1:	return TOPO_CPU_TYPE_EFFICIENCY;
+		}
+	}
+
+	return TOPO_CPU_TYPE_UNKNOWN;
+}
+
+const char *get_topology_cpu_type_name(struct cpuinfo_x86 *c)
+{
+	switch (get_topology_cpu_type(c)) {
+	case TOPO_CPU_TYPE_PERFORMANCE:
+		return "performance";
+	case TOPO_CPU_TYPE_EFFICIENCY:
+		return "efficiency";
+	default:
+		return "unknown";
+	}
+}
+
 static unsigned int __maybe_unused parse_num_cores_legacy(struct cpuinfo_x86 *c)
 {
 	struct {
@@ -87,6 +118,7 @@ static void parse_topology(struct topo_scan *tscan, bool early)
 		.cu_id			= 0xff,
 		.llc_id			= BAD_APICID,
 		.l2c_id			= BAD_APICID,
+		.cpu_type		= TOPO_CPU_TYPE_UNKNOWN,
 	};
 	struct cpuinfo_x86 *c = tscan->c;
 	struct {
@@ -132,6 +164,8 @@ static void parse_topology(struct topo_scan *tscan, bool early)
 	case X86_VENDOR_INTEL:
 		if (!IS_ENABLED(CONFIG_CPU_SUP_INTEL) || !cpu_parse_topology_ext(tscan))
 			parse_legacy(tscan);
+		if (c->cpuid_level >= 0x1a)
+			c->topo.cpu_type = cpuid_eax(0x1a);
 		break;
 	case X86_VENDOR_HYGON:
 		if (IS_ENABLED(CONFIG_CPU_SUP_HYGON))