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 <[email protected]>
Co-developed-by: Mario Limonciello <[email protected]>
Signed-off-by: Mario Limonciello <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Acked-by: Dave Hansen <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: pa1gupta

arch/x86/include/asm/intel-family.h

@@ -183,4 +183,10 @@
 /* Family 19 */
 #define INTEL_PANTHERCOVE_X		IFM(19, 0x01) /* Diamond Rapids */
 
+/* CPU core types */
+enum intel_cpu_type {
+	INTEL_CPU_TYPE_ATOM = 0x20,
+	INTEL_CPU_TYPE_CORE = 0x40,
+};
+
 #endif /* _ASM_X86_INTEL_FAMILY_H */

arch/x86/include/asm/processor.h

@@ -105,6 +105,24 @@ struct cpuinfo_topology {
 	// Cache level topology IDs
 	u32			llc_id;
 	u32			l2c_id;
+
+	// Hardware defined CPU-type
+	union {
+		u32		cpu_type;
+		struct {
+			// CPUID.1A.EAX[23-0]
+			u32	intel_native_model_id	:24;
+			// CPUID.1A.EAX[31-24]
+			u32	intel_type		:8;
+		};
+		struct {
+			// CPUID 0x80000026.EBX
+			u32	amd_num_processors	:16,
+				amd_power_eff_ranking	:8,
+				amd_native_model_id	:4,
+				amd_type		:4;
+		};
+	};
 };
 
 struct cpuinfo_x86 {

arch/x86/include/asm/topology.h

@@ -114,6 +114,12 @@ enum x86_topology_domains {
 	TOPO_MAX_DOMAIN,
 };
 
+enum x86_topology_cpu_type {
+	TOPO_CPU_TYPE_PERFORMANCE,
+	TOPO_CPU_TYPE_EFFICIENCY,
+	TOPO_CPU_TYPE_UNKNOWN,
+};
+
 struct x86_topology_system {
 	unsigned int	dom_shifts[TOPO_MAX_DOMAIN];
 	unsigned int	dom_size[TOPO_MAX_DOMAIN];
@@ -149,6 +155,9 @@ extern unsigned int __max_threads_per_core;
 extern unsigned int __num_threads_per_package;
 extern unsigned int __num_cores_per_package;
 
+const char *get_topology_cpu_type_name(struct cpuinfo_x86 *c);
+enum x86_topology_cpu_type get_topology_cpu_type(struct cpuinfo_x86 *c);
+
 static inline unsigned int topology_max_packages(void)
 {
 	return __max_logical_packages;

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);

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;
 

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))