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diff --git a/Documentation/arch/x86/topology.rst b/Documentation/arch/x86/topology.rst index 7f58010ea86a..86bec8ac2c4d 100644 --- a/Documentation/arch/x86/topology.rst +++ b/Documentation/arch/x86/topology.rst @@ -47,27 +47,31 @@ AMD nomenclature for package is 'Node'. Package-related topology information in the kernel: - - cpuinfo_x86.x86_max_cores: + - topology_num_threads_per_package() - The number of cores in a package. This information is retrieved via CPUID. + The number of threads in a package. - - cpuinfo_x86.x86_max_dies: + - topology_num_cores_per_package() - The number of dies in a package. This information is retrieved via CPUID. + The number of cores in a package. - - cpuinfo_x86.cpu_die_id: + - topology_max_dies_per_package() - The physical ID of the die. This information is retrieved via CPUID. + The maximum number of dies in a package. - - cpuinfo_x86.phys_proc_id: + - cpuinfo_x86.topo.die_id: + + The physical ID of the die. + + - cpuinfo_x86.topo.pkg_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. Modern systems use this value for the socket. There may be multiple - packages within a socket. This value may differ from cpu_die_id. + packages within a socket. This value may differ from topo.die_id. - - cpuinfo_x86.logical_proc_id: + - cpuinfo_x86.topo.logical_pkg_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 @@ -79,9 +83,7 @@ Package-related topology information in the kernel: The maximum possible number of packages in the system. Helpful for per package facilities to preallocate per package information. - - cpu_llc_id: - - A per-CPU variable containing: + - cpuinfo_x86.topo.llc_id: - On Intel, the first APIC ID of the list of CPUs sharing the Last Level Cache @@ -98,16 +100,6 @@ 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 @@ -143,6 +135,201 @@ Thread-related topology information in the kernel: The ID of the core to which a thread belongs. It is also printed in /proc/cpuinfo "core_id." + - topology_logical_core_id(); + + The logical core ID to which a thread belongs. + + + +System topology enumeration +=========================== + +The topology on x86 systems can be discovered using a combination of vendor +specific CPUID leaves which enumerate the processor topology and the cache +hierarchy. + +The CPUID leaves in their preferred order of parsing for each x86 vendor is as +follows: + +1) AMD + + 1) CPUID leaf 0x80000026 [Extended CPU Topology] (Core::X86::Cpuid::ExCpuTopology) + + The extended CPUID leaf 0x80000026 is the extension of the CPUID leaf 0xB + and provides the topology information of Core, Complex, CCD (Die), and + Socket in each level. + + Support for the leaf is discovered by checking if the maximum extended + CPUID level is >= 0x80000026 and then checking if `LogProcAtThisLevel` + in `EBX[15:0]` at a particular level (starting from 0) is non-zero. + + The `LevelType` in `ECX[15:8]` at the level provides the topology domain + the level describes - Core, Complex, CCD(Die), or the Socket. + + The kernel uses the `CoreMaskWidth` from `EAX[4:0]` to discover the + number of bits that need to be right-shifted from `ExtendedLocalApicId` + in `EDX[31:0]` in order to get a unique Topology ID for the topology + level. CPUs with the same Topology ID share the resources at that level. + + CPUID leaf 0x80000026 also provides more information regarding the power + and efficiency rankings, and about the core type on AMD processors with + heterogeneous characteristics. + + If CPUID leaf 0x80000026 is supported, further parsing is not required. + + 2) CPUID leaf 0x0000000B [Extended Topology Enumeration] (Core::X86::Cpuid::ExtTopEnum) + + The extended CPUID leaf 0x0000000B is the predecessor on the extended + CPUID leaf 0x80000026 and only describes the core, and the socket domains + of the processor topology. + + The support for the leaf is discovered by checking if the maximum supported + CPUID level is >= 0xB and then if `EBX[31:0]` at a particular level + (starting from 0) is non-zero. + + The `LevelType` in `ECX[15:8]` at the level provides the topology domain + that the level describes - Thread, or Processor (Socket). + + The kernel uses the `CoreMaskWidth` from `EAX[4:0]` to discover the + number of bits that need to be right-shifted from the `ExtendedLocalApicId` + in `EDX[31:0]` to get a unique Topology ID for that topology level. CPUs + sharing the Topology ID share the resources at that level. + + If CPUID leaf 0xB is supported, further parsing is not required. + + + 3) CPUID leaf 0x80000008 ECX [Size Identifiers] (Core::X86::Cpuid::SizeId) + + If neither the CPUID leaf 0x80000026 nor 0xB is supported, the number of + CPUs on the package is detected using the Size Identifier leaf + 0x80000008 ECX. + + The support for the leaf is discovered by checking if the supported + extended CPUID level is >= 0x80000008. + + The shifts from the APIC ID for the Socket ID is calculated from the + `ApicIdSize` field in `ECX[15:12]` if it is non-zero. + + If `ApicIdSize` is reported to be zero, the shift is calculated as the + order of the `number of threads` calculated from `NC` field in + `ECX[7:0]` which describes the `number of threads - 1` on the package. + + Unless Extended APIC ID is supported, the APIC ID used to find the + Socket ID is from the `LocalApicId` field of CPUID leaf 0x00000001 + `EBX[31:24]`. + + The topology parsing continues to detect if Extended APIC ID is + supported or not. + + + 4) CPUID leaf 0x8000001E [Extended APIC ID, Core Identifiers, Node Identifiers] + (Core::X86::Cpuid::{ExtApicId,CoreId,NodeId}) + + The support for Extended APIC ID can be detected by checking for the + presence of `TopologyExtensions` in `ECX[22]` of CPUID leaf 0x80000001 + [Feature Identifiers] (Core::X86::Cpuid::FeatureExtIdEcx). + + If Topology Extensions is supported, the APIC ID from `ExtendedApicId` + from CPUID leaf 0x8000001E `EAX[31:0]` should be preferred over that from + `LocalApicId` field of CPUID leaf 0x00000001 `EBX[31:24]` for topology + enumeration. + + On processors of Family 0x17 and above that do not support CPUID leaf + 0x80000026 or CPUID leaf 0xB, the shifts from the APIC ID for the Core + ID is calculated using the order of `number of threads per core` + calculated using the `ThreadsPerCore` field in `EBX[15:8]` which + describes `number of threads per core - 1`. + + On Processors of Family 0x15, the Core ID from `EBX[7:0]` is used as the + `cu_id` (Compute Unit ID) to detect CPUs that share the compute units. + + + All AMD processors that support the `TopologyExtensions` feature store the + `NodeId` from the `ECX[7:0]` of CPUID leaf 0x8000001E + (Core::X86::Cpuid::NodeId) as the per-CPU `node_id`. On older processors, + the `node_id` was discovered using MSR_FAM10H_NODE_ID MSR (MSR + 0x0xc001_100c). The presence of the NODE_ID MSR was detected by checking + `ECX[19]` of CPUID leaf 0x80000001 [Feature Identifiers] + (Core::X86::Cpuid::FeatureExtIdEcx). + + +2) Intel + + On Intel platforms, the CPUID leaves that enumerate the processor + topology are as follows: + + 1) CPUID leaf 0x1F (V2 Extended Topology Enumeration Leaf) + + The CPUID leaf 0x1F is the extension of the CPUID leaf 0xB and provides + the topology information of Core, Module, Tile, Die, DieGrp, and Socket + in each level. + + The support for the leaf is discovered by checking if the supported + CPUID level is >= 0x1F and then `EBX[31:0]` at a particular level + (starting from 0) is non-zero. + + The `Domain Type` in `ECX[15:8]` of the sub-leaf provides the topology + domain that the level describes - Core, Module, Tile, Die, DieGrp, and + Socket. + + The kernel uses the value from `EAX[4:0]` to discover the number of + bits that need to be right shifted from the `x2APIC ID` in `EDX[31:0]` + to get a unique Topology ID for the topology level. CPUs with the same + Topology ID share the resources at that level. + + If CPUID leaf 0x1F is supported, further parsing is not required. + + + 2) CPUID leaf 0x0000000B (Extended Topology Enumeration Leaf) + + The extended CPUID leaf 0x0000000B is the predecessor of the V2 Extended + Topology Enumeration Leaf 0x1F and only describes the core, and the + socket domains of the processor topology. + + The support for the leaf is iscovered by checking if the supported CPUID + level is >= 0xB and then checking if `EBX[31:0]` at a particular level + (starting from 0) is non-zero. + + CPUID leaf 0x0000000B shares the same layout as CPUID leaf 0x1F and + should be enumerated in a similar manner. + + If CPUID leaf 0xB is supported, further parsing is not required. + + + 3) CPUID leaf 0x00000004 (Deterministic Cache Parameters Leaf) + + On Intel processors that support neither CPUID leaf 0x1F, nor CPUID leaf + 0xB, the shifts for the SMT domains is calculated using the number of + CPUs sharing the L1 cache. + + Processors that feature Hyper-Threading is detected using `EDX[28]` of + CPUID leaf 0x1 (Basic CPUID Information). + + The order of `Maximum number of addressable IDs for logical processors + sharing this cache` from `EAX[25:14]` of level-0 of CPUID 0x4 provides + the shifts from the APIC ID required to compute the Core ID. + + The APIC ID and Package information is computed using the data from + CPUID leaf 0x1. + + + 4) CPUID leaf 0x00000001 (Basic CPUID Information) + + The mask and shifts to derive the Physical Package (socket) ID is + computed using the `Maximum number of addressable IDs for logical + processors in this physical package` from `EBX[23:16]` of CPUID leaf + 0x1. + + The APIC ID on the legacy platforms is derived from the `Initial APIC + ID` field from `EBX[31:24]` of CPUID leaf 0x1. + + +3) Centaur and Zhaoxin + + Similar to Intel, Centaur and Zhaoxin use a combination of CPUID leaf + 0x00000004 (Deterministic Cache Parameters Leaf) and CPUID leaf 0x00000001 + (Basic CPUID Information) to derive the topology information. + System topology examples |