[PATCH 1/4] x86/topology: Fix AMD core count

[PATCH 1/4] x86/topology: Fix AMD core count

[Borislav Petkov]

From: Peter Zijlstra <peterz@infradead.org>

It turns out AMD gets x86_max_cores wrong when there are compute
units.

The issue is that Linux assumes:

	nr_logical_cpus = nr_cores * nr_siblings

But AMD reports its CU unit as 2 cores, but then sets num_smp_siblings
to 2 as well.

Boris: fixup ras/mce_amd_inj.c too, to compute the Node Base Core
properly, according to the new nomenclature.

Reported-by: Xiong Zhou <jencce.kernel@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andreas Herrmann <aherrmann@suse.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Fixes: 1f12e32f4cd5 ("x86/topology: Create logical package id")
Link: http://lkml.kernel.org/r/20160317095220.GO6344@twins.programming.kicks-ass.net
Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/include/asm/smp.h | 1 +
 arch/x86/kernel/cpu/amd.c  | 8 ++++----
 arch/x86/ras/mce_amd_inj.c | 3 ++-
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 20a3de5cb3b0..66b057306f40 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -155,6 +155,7 @@ static inline int wbinvd_on_all_cpus(void)
 	wbinvd();
 	return 0;
 }
+#define smp_num_siblings	1
 #endif /* CONFIG_SMP */
 
 extern unsigned disabled_cpus;
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index b39338c4b260..b8d7f3012340 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -310,9 +310,9 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
 		node_id = ecx & 7;
 
 		/* get compute unit information */
-		smp_num_siblings = ((ebx >> 8) & 3) + 1;
+		cores_per_cu = smp_num_siblings = ((ebx >> 8) & 3) + 1;
+		c->x86_max_cores /= smp_num_siblings;
 		c->compute_unit_id = ebx & 0xff;
-		cores_per_cu += ((ebx >> 8) & 3);
 	} else if (cpu_has(c, X86_FEATURE_NODEID_MSR)) {
 		u64 value;
 
@@ -328,8 +328,8 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
 		u32 cus_per_node;
 
 		set_cpu_cap(c, X86_FEATURE_AMD_DCM);
-		cores_per_node = c->x86_max_cores / nodes_per_socket;
-		cus_per_node = cores_per_node / cores_per_cu;
+		cus_per_node = c->x86_max_cores / nodes_per_socket;
+		cores_per_node = cus_per_node * cores_per_cu;
 
 		/* store NodeID, use llc_shared_map to store sibling info */
 		per_cpu(cpu_llc_id, cpu) = node_id;
diff --git a/arch/x86/ras/mce_amd_inj.c b/arch/x86/ras/mce_amd_inj.c
index 55d38cfa46c2..9e02dcaef683 100644
--- a/arch/x86/ras/mce_amd_inj.c
+++ b/arch/x86/ras/mce_amd_inj.c
@@ -20,6 +20,7 @@
 #include <linux/pci.h>
 
 #include <asm/mce.h>
+#include <asm/smp.h>
 #include <asm/amd_nb.h>
 #include <asm/irq_vectors.h>
 
@@ -206,7 +207,7 @@ static u32 get_nbc_for_node(int node_id)
 	struct cpuinfo_x86 *c = &boot_cpu_data;
 	u32 cores_per_node;
 
-	cores_per_node = c->x86_max_cores / amd_get_nodes_per_socket();
+	cores_per_node = (c->x86_max_cores * smp_num_siblings) / amd_get_nodes_per_socket();
 
 	return cores_per_node * node_id;
 }
-- 
2.7.3

[PATCH 2/4] perf/amd: Cleanup Fam10h NB event constraints

[Borislav Petkov]

From: Peter Zijlstra <peterz@infradead.org>

Avoid allocating the AMD NB event constraints data structure when not
needed. This gets rid of x86_max_cores usage and avoids allocating
this on AMD Core Perfctr supporting hardware (which has separate MSRs
for NB events).

Cc: Rui Huang <ray.huang@amd.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: aherrmann@suse.com
Cc: jencce.kernel@gmail.com
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20160320124629.GY6375@twins.programming.kicks-ass.net
Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/events/amd/core.c   | 21 ++++++++++++++++++---
 arch/x86/events/perf_event.h |  5 +++++
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
index 049ada8d4e9c..86a9bec18dab 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -369,7 +369,7 @@ static int amd_pmu_cpu_prepare(int cpu)
 
 	WARN_ON_ONCE(cpuc->amd_nb);
 
-	if (boot_cpu_data.x86_max_cores < 2)
+	if (!x86_pmu.amd_nb_constraints)
 		return NOTIFY_OK;
 
 	cpuc->amd_nb = amd_alloc_nb(cpu);
@@ -388,7 +388,7 @@ static void amd_pmu_cpu_starting(int cpu)
 
 	cpuc->perf_ctr_virt_mask = AMD64_EVENTSEL_HOSTONLY;
 
-	if (boot_cpu_data.x86_max_cores < 2)
+	if (!x86_pmu.amd_nb_constraints)
 		return;
 
 	nb_id = amd_get_nb_id(cpu);
@@ -414,7 +414,7 @@ static void amd_pmu_cpu_dead(int cpu)
 {
 	struct cpu_hw_events *cpuhw;
 
-	if (boot_cpu_data.x86_max_cores < 2)
+	if (!x86_pmu.amd_nb_constraints)
 		return;
 
 	cpuhw = &per_cpu(cpu_hw_events, cpu);
@@ -648,6 +648,8 @@ static __initconst const struct x86_pmu amd_pmu = {
 	.cpu_prepare		= amd_pmu_cpu_prepare,
 	.cpu_starting		= amd_pmu_cpu_starting,
 	.cpu_dead		= amd_pmu_cpu_dead,
+
+	.amd_nb_constraints	= 1,
 };
 
 static int __init amd_core_pmu_init(void)
@@ -674,6 +676,11 @@ static int __init amd_core_pmu_init(void)
 	x86_pmu.eventsel	= MSR_F15H_PERF_CTL;
 	x86_pmu.perfctr		= MSR_F15H_PERF_CTR;
 	x86_pmu.num_counters	= AMD64_NUM_COUNTERS_CORE;
+	/*
+	 * AMD Core perfctr has separate MSRs for the NB events, see
+	 * the amd/uncore.c driver.
+	 */
+	x86_pmu.amd_nb_constraints = 0;
 
 	pr_cont("core perfctr, ");
 	return 0;
@@ -693,6 +700,14 @@ __init int amd_pmu_init(void)
 	if (ret)
 		return ret;
 
+	if (num_possible_cpus() == 1) {
+		/*
+		 * No point in allocating data structures to serialize
+		 * against other CPUs, when there is only the one CPU.
+		 */
+		x86_pmu.amd_nb_constraints = 0;
+	}
+
 	/* Events are common for all AMDs */
 	memcpy(hw_cache_event_ids, amd_hw_cache_event_ids,
 	       sizeof(hw_cache_event_ids));
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index ba6ef18528c9..716d0482f5db 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -608,6 +608,11 @@ struct x86_pmu {
 	atomic_t	lbr_exclusive[x86_lbr_exclusive_max];
 
 	/*
+	 * AMD bits
+	 */
+	unsigned int	amd_nb_constraints : 1;
+
+	/*
 	 * Extra registers for events
 	 */
 	struct extra_reg *extra_regs;
-- 
2.7.3

[PATCH 3/4] x86/cpu: Get rid of compute_unit_id

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

It is cpu_core_id anyway.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/include/asm/processor.h |  2 --
 arch/x86/kernel/amd_nb.c         |  6 ++----
 arch/x86/kernel/cpu/amd.c        | 10 +++-------
 arch/x86/kernel/smpboot.c        |  2 +-
 4 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 983738ac014c..9264476f3d57 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -132,8 +132,6 @@ struct cpuinfo_x86 {
 	u16			logical_proc_id;
 	/* Core id: */
 	u16			cpu_core_id;
-	/* Compute unit id */
-	u8			compute_unit_id;
 	/* Index into per_cpu list: */
 	u16			cpu_index;
 	u32			microcode;
diff --git a/arch/x86/kernel/amd_nb.c b/arch/x86/kernel/amd_nb.c
index 29fa475ec518..a147e676fc7b 100644
--- a/arch/x86/kernel/amd_nb.c
+++ b/arch/x86/kernel/amd_nb.c
@@ -170,15 +170,13 @@ int amd_get_subcaches(int cpu)
 {
 	struct pci_dev *link = node_to_amd_nb(amd_get_nb_id(cpu))->link;
 	unsigned int mask;
-	int cuid;
 
 	if (!amd_nb_has_feature(AMD_NB_L3_PARTITIONING))
 		return 0;
 
 	pci_read_config_dword(link, 0x1d4, &mask);
 
-	cuid = cpu_data(cpu).compute_unit_id;
-	return (mask >> (4 * cuid)) & 0xf;
+	return (mask >> (4 * cpu_data(cpu).cpu_core_id)) & 0xf;
 }
 
 int amd_set_subcaches(int cpu, unsigned long mask)
@@ -204,7 +202,7 @@ int amd_set_subcaches(int cpu, unsigned long mask)
 		pci_write_config_dword(nb->misc, 0x1b8, reg & ~0x180000);
 	}
 
-	cuid = cpu_data(cpu).compute_unit_id;
+	cuid = cpu_data(cpu).cpu_core_id;
 	mask <<= 4 * cuid;
 	mask |= (0xf ^ (1 << cuid)) << 26;
 
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index b8d7f3012340..fb0f5dddfbaa 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -297,7 +297,6 @@ static int nearby_node(int apicid)
 #ifdef CONFIG_SMP
 static void amd_get_topology(struct cpuinfo_x86 *c)
 {
-	u32 cores_per_cu = 1;
 	u8 node_id;
 	int cpu = smp_processor_id();
 
@@ -310,9 +309,9 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
 		node_id = ecx & 7;
 
 		/* get compute unit information */
-		cores_per_cu = smp_num_siblings = ((ebx >> 8) & 3) + 1;
+		smp_num_siblings = ((ebx >> 8) & 3) + 1;
 		c->x86_max_cores /= smp_num_siblings;
-		c->compute_unit_id = ebx & 0xff;
+		c->cpu_core_id = ebx & 0xff;
 	} else if (cpu_has(c, X86_FEATURE_NODEID_MSR)) {
 		u64 value;
 
@@ -324,19 +323,16 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
 
 	/* fixup multi-node processor information */
 	if (nodes_per_socket > 1) {
-		u32 cores_per_node;
 		u32 cus_per_node;
 
 		set_cpu_cap(c, X86_FEATURE_AMD_DCM);
 		cus_per_node = c->x86_max_cores / nodes_per_socket;
-		cores_per_node = cus_per_node * cores_per_cu;
 
 		/* store NodeID, use llc_shared_map to store sibling info */
 		per_cpu(cpu_llc_id, cpu) = node_id;
 
 		/* core id has to be in the [0 .. cores_per_node - 1] range */
-		c->cpu_core_id %= cores_per_node;
-		c->compute_unit_id %= cus_per_node;
+		c->cpu_core_id %= cus_per_node;
 	}
 }
 #endif
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index b2c99f811c3f..a2065d3b3b39 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -422,7 +422,7 @@ static bool match_smt(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
 
 		if (c->phys_proc_id == o->phys_proc_id &&
 		    per_cpu(cpu_llc_id, cpu1) == per_cpu(cpu_llc_id, cpu2) &&
-		    c->compute_unit_id == o->compute_unit_id)
+		    c->cpu_core_id == o->cpu_core_id)
 			return topology_sane(c, o, "smt");
 
 	} else if (c->phys_proc_id == o->phys_proc_id &&
-- 
2.7.3

[tip:x86/urgent] x86/cpu: Get rid of compute_unit_id

[tip-bot for Borislav Petkov]

Commit-ID:  8196dab4fc159943df6baaac04973bb1accb7100
Gitweb:     http://git.kernel.org/tip/8196dab4fc159943df6baaac04973bb1accb7100
Author:     Borislav Petkov <bp@suse.de>
AuthorDate: Fri, 25 Mar 2016 15:52:36 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 29 Mar 2016 10:45:04 +0200

x86/cpu: Get rid of compute_unit_id

It is cpu_core_id anyway.

Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1458917557-8757-3-git-send-email-bp@alien8.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 arch/x86/include/asm/processor.h |  2 --
 arch/x86/kernel/amd_nb.c         |  6 ++----
 arch/x86/kernel/cpu/amd.c        | 10 +++-------
 arch/x86/kernel/smpboot.c        |  2 +-
 4 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 983738a..9264476 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -132,8 +132,6 @@ struct cpuinfo_x86 {
 	u16			logical_proc_id;
 	/* Core id: */
 	u16			cpu_core_id;
-	/* Compute unit id */
-	u8			compute_unit_id;
 	/* Index into per_cpu list: */
 	u16			cpu_index;
 	u32			microcode;
diff --git a/arch/x86/kernel/amd_nb.c b/arch/x86/kernel/amd_nb.c
index 29fa475..a147e67 100644
--- a/arch/x86/kernel/amd_nb.c
+++ b/arch/x86/kernel/amd_nb.c
@@ -170,15 +170,13 @@ int amd_get_subcaches(int cpu)
 {
 	struct pci_dev *link = node_to_amd_nb(amd_get_nb_id(cpu))->link;
 	unsigned int mask;
-	int cuid;
 
 	if (!amd_nb_has_feature(AMD_NB_L3_PARTITIONING))
 		return 0;
 
 	pci_read_config_dword(link, 0x1d4, &mask);
 
-	cuid = cpu_data(cpu).compute_unit_id;
-	return (mask >> (4 * cuid)) & 0xf;
+	return (mask >> (4 * cpu_data(cpu).cpu_core_id)) & 0xf;
 }
 
 int amd_set_subcaches(int cpu, unsigned long mask)
@@ -204,7 +202,7 @@ int amd_set_subcaches(int cpu, unsigned long mask)
 		pci_write_config_dword(nb->misc, 0x1b8, reg & ~0x180000);
 	}
 
-	cuid = cpu_data(cpu).compute_unit_id;
+	cuid = cpu_data(cpu).cpu_core_id;
 	mask <<= 4 * cuid;
 	mask |= (0xf ^ (1 << cuid)) << 26;
 
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 4d0087f..7b76eb6 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -300,7 +300,6 @@ static int nearby_node(int apicid)
 #ifdef CONFIG_SMP
 static void amd_get_topology(struct cpuinfo_x86 *c)
 {
-	u32 cores_per_cu = 1;
 	u8 node_id;
 	int cpu = smp_processor_id();
 
@@ -312,9 +311,9 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
 		node_id = ecx & 7;
 
 		/* get compute unit information */
-		cores_per_cu = smp_num_siblings = ((ebx >> 8) & 3) + 1;
+		smp_num_siblings = ((ebx >> 8) & 3) + 1;
 		c->x86_max_cores /= smp_num_siblings;
-		c->compute_unit_id = ebx & 0xff;
+		c->cpu_core_id = ebx & 0xff;
 	} else if (cpu_has(c, X86_FEATURE_NODEID_MSR)) {
 		u64 value;
 
@@ -325,19 +324,16 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
 
 	/* fixup multi-node processor information */
 	if (nodes_per_socket > 1) {
-		u32 cores_per_node;
 		u32 cus_per_node;
 
 		set_cpu_cap(c, X86_FEATURE_AMD_DCM);
 		cus_per_node = c->x86_max_cores / nodes_per_socket;
-		cores_per_node = cus_per_node * cores_per_cu;
 
 		/* store NodeID, use llc_shared_map to store sibling info */
 		per_cpu(cpu_llc_id, cpu) = node_id;
 
 		/* core id has to be in the [0 .. cores_per_node - 1] range */
-		c->cpu_core_id %= cores_per_node;
-		c->compute_unit_id %= cus_per_node;
+		c->cpu_core_id %= cus_per_node;
 	}
 }
 #endif
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index b2c99f8..a2065d3 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -422,7 +422,7 @@ static bool match_smt(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
 
 		if (c->phys_proc_id == o->phys_proc_id &&
 		    per_cpu(cpu_llc_id, cpu1) == per_cpu(cpu_llc_id, cpu2) &&
-		    c->compute_unit_id == o->compute_unit_id)
+		    c->cpu_core_id == o->cpu_core_id)
 			return topology_sane(c, o, "smt");
 
 	} else if (c->phys_proc_id == o->phys_proc_id &&

[PATCH 4/4] x86/Documentation: Start documenting x86 topology

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

This should contain important aspects of how we represent the system
topology on x86. If people have questions about it and this file doesn't
answer it, then it must be updated.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
 Documentation/x86/topology.txt | 202 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 202 insertions(+)
 create mode 100644 Documentation/x86/topology.txt

diff --git a/Documentation/x86/topology.txt b/Documentation/x86/topology.txt
new file mode 100644
index 000000000000..d393a2beecc0
--- /dev/null
+++ b/Documentation/x86/topology.txt
@@ -0,0 +1,202 @@
+x86 Topology
+============
+
+This documents and clarifies the main aspects of x86 topology modelling
+and representation in the kernel. Update/change when doing changes to
+the respective code.
+
+Started by Thomas Gleixner <tglx@linutronix.de> and Borislav Petkov <bp@alien8.de>.
+
+The main aim of the topology facilities is to present adequate
+interfaces to code which needs to know/query/use the structure of the
+running system wrt threads, cores, packages, etc.
+
+The kernel does not care about the concept of physical sockets because
+a socket has no relevance to software. It's an electromechanical
+component. In the past a socket always contained a single package
+(see below), but with the advent of Multi Chip Modules (MCM) a socket
+can hold more than one package. So there might be still references to
+sockets in the code, but they are of historical nature and should be
+cleaned up.
+
+The topology of a system is described in the units of:
+
+    - packages
+    - cores
+    - threads
+
+* Package:
+
+  Packages contain a number of cores plus shared resources, e.g. DRAM
+  controller, shared caches etc.
+
+  AMD nomenclature for package is 'Node'.
+
+  Package-related topology information in the kernel:
+
+  - cpuinfo_x86.x86_max_cores:
+
+    The number of cores in a package. This information is retrieved via CPUID.
+
+  - cpuinfo_x86.phys_proc_id:
+
+    The physical ID of the package. This information is retrieved via CPUID
+    and deduced from the APIC IDs of the cores in the package.
+
+  - cpuinfo_x86.logical_id:
+
+    The logical ID of the package. As we do not trust BIOSes to enumerate the
+    packages in a consistent way, we introduced the concept of logical package
+    ID so we can sanely calculate the number of maximum possible packages in
+    the system and have the packages enumerated linearly.
+
+  - topology_max_packages():
+
+    The maximum possible number of packages in the system. Helpful for per
+    package facilities to preallocate per package information.
+
+
+* Cores:
+
+  A core consists of 1 or more threads. It does not matter whether the threads
+  are SMT- or CMT-type threads.
+
+  AMDs nomenclature for a CMT core is "Compute Unit". The kernel always uses
+  "core".
+
+  Core-related topology information in the kernel:
+
+  - smp_num_siblings:
+
+    The number of threads in a core. The number of threads in a package can be
+    calculated by:
+
+    	threads_per_package = cpuinfo_x86.x86_max_cores * smp_num_siblings
+
+
+* Threads:
+
+  A thread is a single scheduling unit. It's the equivalent to a logical Linux
+  CPU.
+
+  AMDs nomenclature for CMT threads is "Compute Unit Core". The kernel always
+  uses "thread".
+
+  Thread-related topology information in the kernel:
+
+  - topology_core_cpumask():
+
+    The cpumask contains all online threads in the package to which a thread
+    belongs.
+
+    The number of online threads is also printed in /proc/cpuinfo "siblings."
+
+  - topology_sibling_mask():
+
+    The cpumask contains all online threads in the core to which a thread
+    belongs.
+
+   - topology_logical_package_id():
+
+    The logical package ID to which a thread belongs.
+
+   - topology_physical_package_id():
+
+    The physical package ID to which a thread belongs.
+
+   - topology_core_id();
+
+    The ID of the core to which a thread belongs. It is also printed in /proc/cpuinfo
+    "core_id."
+
+
+
+System topology examples
+
+Note:
+
+The alternative Linux CPU enumeration depends on how the BIOS enumerates the
+threads. Many BIOSes enumerate all threads 0 first and then all threads 1.
+That has the "advantage" that the logical Linux CPU numbers of threads 0 stay
+the same whether threads are enabled or not. That's merely an implementation
+detail and has no practical impact.
+
+1) Single Package, Single Core
+
+   [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+
+2) Single Package, Dual Core
+
+   a) One thread per core
+
+      [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+	          -> [core 1] -> [thread 0] -> Linux CPU 1
+
+   b) Two threads per core
+
+      [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+   	         	      -> [thread 1] -> Linux CPU 1
+      	          -> [core 1] -> [thread 0] -> Linux CPU 2
+   	         	      -> [thread 1] -> Linux CPU 3
+
+      Alternative enumeration:
+
+      [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+   	         	      -> [thread 1] -> Linux CPU 2
+      	          -> [core 1] -> [thread 0] -> Linux CPU 1
+   	         	      -> [thread 1] -> Linux CPU 3
+
+      AMD nomenclature for CMT systems:
+
+      [node 0] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 0
+   	       		           -> [Compute Unit Core 1] -> Linux CPU 1
+               -> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 2
+   	       		           -> [Compute Unit Core 1] -> Linux CPU 3
+
+4) Dual Package, Dual Core
+
+   a) One thread per core
+
+      [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+    	          -> [core 1] -> [thread 0] -> Linux CPU 1
+
+      [package 1] -> [core 0] -> [thread 0] -> Linux CPU 2
+   	          -> [core 1] -> [thread 0] -> Linux CPU 3
+
+   b) Two threads per core
+
+      [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+   	           	      -> [thread 1] -> Linux CPU 1
+      	          -> [core 1] -> [thread 0] -> Linux CPU 2
+   	         	      -> [thread 1] -> Linux CPU 3
+
+      [package 1] -> [core 0] -> [thread 0] -> Linux CPU 4
+   	         	      -> [thread 1] -> Linux CPU 5
+      	          -> [core 1] -> [thread 0] -> Linux CPU 6
+   	         	      -> [thread 1] -> Linux CPU 7
+
+      Alternative enumeration:
+
+      [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+   	         	      -> [thread 1] -> Linux CPU 4
+       	          -> [core 1] -> [thread 0] -> Linux CPU 1
+   	         	      -> [thread 1] -> Linux CPU 5
+
+      [package 1] -> [core 0] -> [thread 0] -> Linux CPU 2
+   	         	      -> [thread 1] -> Linux CPU 6
+      	          -> [core 1] -> [thread 0] -> Linux CPU 3
+   	         	      -> [thread 1] -> Linux CPU 7
+
+      AMD nomenclature for CMT systems:
+
+      [node 0] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 0
+   	       		           -> [Compute Unit Core 1] -> Linux CPU 1
+               -> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 2
+   	       		           -> [Compute Unit Core 1] -> Linux CPU 3
+
+      [node 1] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 4
+   	       		           -> [Compute Unit Core 1] -> Linux CPU 5
+               -> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 6
+   	       		           -> [Compute Unit Core 1] -> Linux CPU 7
+
+
-- 
2.7.3

[PATCH 4/4 -v1.1] x86/Documentation: Start documenting x86 topology

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

This should contain important aspects of how we represent the system
topology on x86. If people have questions about it and this file doesn't
answer it, then it must be updated.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
---

Let me add a reference to the generic topology document
Documentation/cputopology.txt too.

 Documentation/x86/topology.txt | 212 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 212 insertions(+)
 create mode 100644 Documentation/x86/topology.txt

diff --git a/Documentation/x86/topology.txt b/Documentation/x86/topology.txt
new file mode 100644
index 000000000000..75021f128848
--- /dev/null
+++ b/Documentation/x86/topology.txt
@@ -0,0 +1,212 @@
+x86 Topology
+============
+
+This documents and clarifies the main aspects of x86 topology modelling
+and representation in the kernel. Update/change when doing changes to
+the respective code.
+
+The architecture-agnostic topology definitions are in
+Documentation/cputopology.txt. This file holds x86-specific
+differences/specialities which must not necessarily apply to the generic
+definitions. Thus, the way to read up on Linux topology on x86 is to
+start with the generic one and look at this one in parallel for the x86
+specifics.
+
+Needless to say, code should use the generic functions - this file is
+*only* here to *document* the inner workings of x86 topology.
+
+Started by Thomas Gleixner <tglx@linutronix.de> and Borislav Petkov <bp@alien8.de>.
+
+The main aim of the topology facilities is to present adequate
+interfaces to code which needs to know/query/use the structure of the
+running system wrt threads, cores, packages, etc.
+
+The kernel does not care about the concept of physical sockets because
+a socket has no relevance to software. It's an electromechanical
+component. In the past a socket always contained a single package
+(see below), but with the advent of Multi Chip Modules (MCM) a socket
+can hold more than one package. So there might be still references to
+sockets in the code, but they are of historical nature and should be
+cleaned up.
+
+The topology of a system is described in the units of:
+
+    - packages
+    - cores
+    - threads
+
+* Package:
+
+  Packages contain a number of cores plus shared resources, e.g. DRAM
+  controller, shared caches etc.
+
+  AMD nomenclature for package is 'Node'.
+
+  Package-related topology information in the kernel:
+
+  - cpuinfo_x86.x86_max_cores:
+
+    The number of cores in a package. This information is retrieved via CPUID.
+
+  - cpuinfo_x86.phys_proc_id:
+
+    The physical ID of the package. This information is retrieved via CPUID
+    and deduced from the APIC IDs of the cores in the package.
+
+  - cpuinfo_x86.logical_id:
+
+    The logical ID of the package. As we do not trust BIOSes to enumerate the
+    packages in a consistent way, we introduced the concept of logical package
+    ID so we can sanely calculate the number of maximum possible packages in
+    the system and have the packages enumerated linearly.
+
+  - topology_max_packages():
+
+    The maximum possible number of packages in the system. Helpful for per
+    package facilities to preallocate per package information.
+
+
+* Cores:
+
+  A core consists of 1 or more threads. It does not matter whether the threads
+  are SMT- or CMT-type threads.
+
+  AMDs nomenclature for a CMT core is "Compute Unit". The kernel always uses
+  "core".
+
+  Core-related topology information in the kernel:
+
+  - smp_num_siblings:
+
+    The number of threads in a core. The number of threads in a package can be
+    calculated by:
+
+    	threads_per_package = cpuinfo_x86.x86_max_cores * smp_num_siblings
+
+
+* Threads:
+
+  A thread is a single scheduling unit. It's the equivalent to a logical Linux
+  CPU.
+
+  AMDs nomenclature for CMT threads is "Compute Unit Core". The kernel always
+  uses "thread".
+
+  Thread-related topology information in the kernel:
+
+  - topology_core_cpumask():
+
+    The cpumask contains all online threads in the package to which a thread
+    belongs.
+
+    The number of online threads is also printed in /proc/cpuinfo "siblings."
+
+  - topology_sibling_mask():
+
+    The cpumask contains all online threads in the core to which a thread
+    belongs.
+
+   - topology_logical_package_id():
+
+    The logical package ID to which a thread belongs.
+
+   - topology_physical_package_id():
+
+    The physical package ID to which a thread belongs.
+
+   - topology_core_id();
+
+    The ID of the core to which a thread belongs. It is also printed in /proc/cpuinfo
+    "core_id."
+
+
+
+System topology examples
+
+Note:
+
+The alternative Linux CPU enumeration depends on how the BIOS enumerates the
+threads. Many BIOSes enumerate all threads 0 first and then all threads 1.
+That has the "advantage" that the logical Linux CPU numbers of threads 0 stay
+the same whether threads are enabled or not. That's merely an implementation
+detail and has no practical impact.
+
+1) Single Package, Single Core
+
+   [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+
+2) Single Package, Dual Core
+
+   a) One thread per core
+
+      [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+	          -> [core 1] -> [thread 0] -> Linux CPU 1
+
+   b) Two threads per core
+
+      [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+   	         	      -> [thread 1] -> Linux CPU 1
+      	          -> [core 1] -> [thread 0] -> Linux CPU 2
+   	         	      -> [thread 1] -> Linux CPU 3
+
+      Alternative enumeration:
+
+      [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+   	         	      -> [thread 1] -> Linux CPU 2
+      	          -> [core 1] -> [thread 0] -> Linux CPU 1
+   	         	      -> [thread 1] -> Linux CPU 3
+
+      AMD nomenclature for CMT systems:
+
+      [node 0] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 0
+   	       		           -> [Compute Unit Core 1] -> Linux CPU 1
+               -> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 2
+   	       		           -> [Compute Unit Core 1] -> Linux CPU 3
+
+4) Dual Package, Dual Core
+
+   a) One thread per core
+
+      [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+    	          -> [core 1] -> [thread 0] -> Linux CPU 1
+
+      [package 1] -> [core 0] -> [thread 0] -> Linux CPU 2
+   	          -> [core 1] -> [thread 0] -> Linux CPU 3
+
+   b) Two threads per core
+
+      [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+   	           	      -> [thread 1] -> Linux CPU 1
+      	          -> [core 1] -> [thread 0] -> Linux CPU 2
+   	         	      -> [thread 1] -> Linux CPU 3
+
+      [package 1] -> [core 0] -> [thread 0] -> Linux CPU 4
+   	         	      -> [thread 1] -> Linux CPU 5
+      	          -> [core 1] -> [thread 0] -> Linux CPU 6
+   	         	      -> [thread 1] -> Linux CPU 7
+
+      Alternative enumeration:
+
+      [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+   	         	      -> [thread 1] -> Linux CPU 4
+       	          -> [core 1] -> [thread 0] -> Linux CPU 1
+   	         	      -> [thread 1] -> Linux CPU 5
+
+      [package 1] -> [core 0] -> [thread 0] -> Linux CPU 2
+   	         	      -> [thread 1] -> Linux CPU 6
+      	          -> [core 1] -> [thread 0] -> Linux CPU 3
+   	         	      -> [thread 1] -> Linux CPU 7
+
+      AMD nomenclature for CMT systems:
+
+      [node 0] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 0
+   	       		           -> [Compute Unit Core 1] -> Linux CPU 1
+               -> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 2
+   	       		           -> [Compute Unit Core 1] -> Linux CPU 3
+
+      [node 1] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 4
+   	       		           -> [Compute Unit Core 1] -> Linux CPU 5
+               -> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 6
+   	       		           -> [Compute Unit Core 1] -> Linux CPU 7
+
+
-- 
2.7.3


-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.

[tip:x86/urgent] x86/Documentation: Start documenting x86 topology

[tip-bot for Borislav Petkov]

Commit-ID:  f7be8610bca88e59dd2fd5d98fcbc5031ef0e079
Gitweb:     http://git.kernel.org/tip/f7be8610bca88e59dd2fd5d98fcbc5031ef0e079
Author:     Borislav Petkov <bp@suse.de>
AuthorDate: Mon, 28 Mar 2016 11:56:09 +0200
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 29 Mar 2016 10:45:04 +0200

x86/Documentation: Start documenting x86 topology

This should contain important aspects of how we represent the system
topology on x86. If people have questions about it and this file doesn't
answer it, then it must be updated.

Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/20160328095609.GD26651@pd.tnic
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 Documentation/x86/topology.txt | 208 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 208 insertions(+)

diff --git a/Documentation/x86/topology.txt b/Documentation/x86/topology.txt
new file mode 100644
index 0000000..06afac2
--- /dev/null
+++ b/Documentation/x86/topology.txt
@@ -0,0 +1,208 @@
+x86 Topology
+============
+
+This documents and clarifies the main aspects of x86 topology modelling and
+representation in the kernel. Update/change when doing changes to the
+respective code.
+
+The architecture-agnostic topology definitions are in
+Documentation/cputopology.txt. This file holds x86-specific
+differences/specialities which must not necessarily apply to the generic
+definitions. Thus, the way to read up on Linux topology on x86 is to start
+with the generic one and look at this one in parallel for the x86 specifics.
+
+Needless to say, code should use the generic functions - this file is *only*
+here to *document* the inner workings of x86 topology.
+
+Started by Thomas Gleixner <tglx@linutronix.de> and Borislav Petkov <bp@alien8.de>.
+
+The main aim of the topology facilities is to present adequate interfaces to
+code which needs to know/query/use the structure of the running system wrt
+threads, cores, packages, etc.
+
+The kernel does not care about the concept of physical sockets because a
+socket has no relevance to software. It's an electromechanical component. In
+the past a socket always contained a single package (see below), but with the
+advent of Multi Chip Modules (MCM) a socket can hold more than one package. So
+there might be still references to sockets in the code, but they are of
+historical nature and should be cleaned up.
+
+The topology of a system is described in the units of:
+
+    - packages
+    - cores
+    - threads
+
+* Package:
+
+  Packages contain a number of cores plus shared resources, e.g. DRAM
+  controller, shared caches etc.
+
+  AMD nomenclature for package is 'Node'.
+
+  Package-related topology information in the kernel:
+
+  - cpuinfo_x86.x86_max_cores:
+
+    The number of cores in a package. This information is retrieved via CPUID.
+
+  - cpuinfo_x86.phys_proc_id:
+
+    The physical ID of the package. This information is retrieved via CPUID
+    and deduced from the APIC IDs of the cores in the package.
+
+  - cpuinfo_x86.logical_id:
+
+    The logical ID of the package. As we do not trust BIOSes to enumerate the
+    packages in a consistent way, we introduced the concept of logical package
+    ID so we can sanely calculate the number of maximum possible packages in
+    the system and have the packages enumerated linearly.
+
+  - topology_max_packages():
+
+    The maximum possible number of packages in the system. Helpful for per
+    package facilities to preallocate per package information.
+
+
+* Cores:
+
+  A core consists of 1 or more threads. It does not matter whether the threads
+  are SMT- or CMT-type threads.
+
+  AMDs nomenclature for a CMT core is "Compute Unit". The kernel always uses
+  "core".
+
+  Core-related topology information in the kernel:
+
+  - smp_num_siblings:
+
+    The number of threads in a core. The number of threads in a package can be
+    calculated by:
+
+	threads_per_package = cpuinfo_x86.x86_max_cores * smp_num_siblings
+
+
+* Threads:
+
+  A thread is a single scheduling unit. It's the equivalent to a logical Linux
+  CPU.
+
+  AMDs nomenclature for CMT threads is "Compute Unit Core". The kernel always
+  uses "thread".
+
+  Thread-related topology information in the kernel:
+
+  - topology_core_cpumask():
+
+    The cpumask contains all online threads in the package to which a thread
+    belongs.
+
+    The number of online threads is also printed in /proc/cpuinfo "siblings."
+
+  - topology_sibling_mask():
+
+    The cpumask contains all online threads in the core to which a thread
+    belongs.
+
+   - topology_logical_package_id():
+
+    The logical package ID to which a thread belongs.
+
+   - topology_physical_package_id():
+
+    The physical package ID to which a thread belongs.
+
+   - topology_core_id();
+
+    The ID of the core to which a thread belongs. It is also printed in /proc/cpuinfo
+    "core_id."
+
+
+
+System topology examples
+
+Note:
+
+The alternative Linux CPU enumeration depends on how the BIOS enumerates the
+threads. Many BIOSes enumerate all threads 0 first and then all threads 1.
+That has the "advantage" that the logical Linux CPU numbers of threads 0 stay
+the same whether threads are enabled or not. That's merely an implementation
+detail and has no practical impact.
+
+1) Single Package, Single Core
+
+   [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+
+2) Single Package, Dual Core
+
+   a) One thread per core
+
+	[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+		    -> [core 1] -> [thread 0] -> Linux CPU 1
+
+   b) Two threads per core
+
+	[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+				-> [thread 1] -> Linux CPU 1
+		    -> [core 1] -> [thread 0] -> Linux CPU 2
+				-> [thread 1] -> Linux CPU 3
+
+      Alternative enumeration:
+
+	[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+				-> [thread 1] -> Linux CPU 2
+		    -> [core 1] -> [thread 0] -> Linux CPU 1
+				-> [thread 1] -> Linux CPU 3
+
+      AMD nomenclature for CMT systems:
+
+	[node 0] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 0
+				     -> [Compute Unit Core 1] -> Linux CPU 1
+		 -> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 2
+				     -> [Compute Unit Core 1] -> Linux CPU 3
+
+4) Dual Package, Dual Core
+
+   a) One thread per core
+
+	[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+		    -> [core 1] -> [thread 0] -> Linux CPU 1
+
+	[package 1] -> [core 0] -> [thread 0] -> Linux CPU 2
+		    -> [core 1] -> [thread 0] -> Linux CPU 3
+
+   b) Two threads per core
+
+	[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+				-> [thread 1] -> Linux CPU 1
+		    -> [core 1] -> [thread 0] -> Linux CPU 2
+				-> [thread 1] -> Linux CPU 3
+
+	[package 1] -> [core 0] -> [thread 0] -> Linux CPU 4
+				-> [thread 1] -> Linux CPU 5
+		    -> [core 1] -> [thread 0] -> Linux CPU 6
+				-> [thread 1] -> Linux CPU 7
+
+      Alternative enumeration:
+
+	[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+				-> [thread 1] -> Linux CPU 4
+		    -> [core 1] -> [thread 0] -> Linux CPU 1
+				-> [thread 1] -> Linux CPU 5
+
+	[package 1] -> [core 0] -> [thread 0] -> Linux CPU 2
+				-> [thread 1] -> Linux CPU 6
+		    -> [core 1] -> [thread 0] -> Linux CPU 3
+				-> [thread 1] -> Linux CPU 7
+
+      AMD nomenclature for CMT systems:
+
+	[node 0] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 0
+				     -> [Compute Unit Core 1] -> Linux CPU 1
+		 -> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 2
+				     -> [Compute Unit Core 1] -> Linux CPU 3
+
+	[node 1] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 4
+				     -> [Compute Unit Core 1] -> Linux CPU 5
+		 -> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 6
+				     -> [Compute Unit Core 1] -> Linux CPU 7