Expand description

A library to parse the x86 CPUID instruction, written in rust with no external dependencies. The implementation closely resembles the Intel CPUID manual description. The library works with no_std.


use raw_cpuid::CpuId;
let cpuid = CpuId::new();

if let Some(vf) = cpuid.get_vendor_info() {
    assert!(vf.as_str() == "GenuineIntel" || vf.as_str() == "AuthenticAMD");

let has_sse = cpuid.get_feature_info().map_or(false, |finfo| finfo.has_sse());
if has_sse {
    println!("CPU supports SSE!");

if let Some(cparams) = cpuid.get_cache_parameters() {
    for cache in cparams {
        let size = cache.associativity() * cache.physical_line_partitions() * cache.coherency_line_size() * cache.sets();
        println!("L{}-Cache size is {}", cache.level(), size);
} else {
    println!("No cache parameter information available")

Platform support

CPU vendors may choose to not support certain functions/leafs in cpuid or only support them partially. We highlight this with the following emojis throughout the documentation:

  • ✅: This struct/function is fully supported by the vendor.
  • 🟡: This struct is partially supported by the vendor, refer to individual functions for more information.
  • ❌: This struct/function is not supported by the vendor. When queried on this platform, we will return None/false/0 (or some other sane default).
  • ❓: This struct/function is not supported by the vendor according to the manual, but the in practice it still may return valid information.

Note that the presence of a ✅ does not guarantee that a specific feature will exist for your CPU – just that it is potentially supported by the vendor on some of its chips. You will still have to query it at runtime.


Uses Rust’s cpuid function from the arch module.


Macro which queries cpuid directly.


Processor Power Management and RAS Capabilities (LEAF=0x8000_0007).

Describes any kind of cache (TLB, Data and Instruction caches plus prefetchers).

Iterates over cache information (LEAF=0x02).

Information about an individual cache in the hierarchy.

Iterator over caches (LEAF=0x04).

The main type used to query information about the CPU we’re running on.

Low-level data-structure to store result of cpuid instruction.

Deterministic Address Translation Structure

Deterministic Address Translation Structure Iterator (LEAF=0x18).

Direct cache access info (LEAF=0x09).

EBX:EAX and EDX:ECX provide information on the Enclave Page Cache (EPC) section

Structured Extended Feature Identifiers (LEAF=0x07).

Extended Processor and Processor Feature Identifiers (LEAF=0x8000_0001)

ExtendedState subleaf structure for things that need to be restored.

Information for saving/restoring extended register state (LEAF=0x0D).

Information about topology (LEAF=0x0B).

Gives information about the current level in the topology.

Processor and Processor Feature Identifiers (LEAF=0x01).

Information about Hypervisor (LEAF=0x4000_0001)

L1 Cache and TLB Information (LEAF=0x8000_0005).

L2/L3 Cache and TLB Information (LEAF=0x8000_0006).

L2 Cache Allocation Technology Enumeration Sub-leaf (LEAF=0x10, SUBLEAF=2).

L3 Cache Allocation Technology Enumeration Sub-leaf (LEAF=0x10, SUBLEAF=1).

Information about L3 cache monitoring.

Memory Bandwidth Allocation Enumeration Sub-leaf (LEAF=0x10, SUBLEAF=3).

Encrypted Memory Capabilities (LEAF=0x8000_001F).

Information about how monitor/mwait works on this CPU (LEAF=0x05).

Info about performance monitoring – how many counters etc. (LEAF=0x0A)

Performance Optimization Identifier (LEAF=0x8000_001A).

Processor name (LEAF=0x8000_0002..=0x8000_0004).

Processor Capacity Parameters and Extended Feature Identification (LEAF=0x8000_0008).

Processor Frequency Information (LEAF=0x16).

Processor Serial Number (LEAF=0x3).

Processor Topology Information (LEAF=0x8000_001E).

Intel Processor Trace Information (LEAF=0x14).

Quality of service enforcement information (LEAF=0x10).

Intel Resource Director Technology RDT (LEAF=0x0F).

Intel SGX Capability Enumeration Leaf (LEAF=0x12).

Iterator over the SGX sub-leafs (ECX >= 2).

Iterator for SoC vendor attributes.

A vendor brand string as queried from the cpuid leaf.

SoC vendor specific information (LEAF=0x17).

Information about the SVM features that the processory supports (LEAF=0x8000_000A).

Query information about thermal and power management features of the CPU (LEAF=0x06).

TLB 1-GiB Pages Information (LEAF=0x8000_0019).

Time Stamp Counter/Core Crystal Clock Information (LEAF=0x15).

Vendor Info String (LEAF=0x0)


Info about cache Associativity.

What type of cache are we dealing with?

Info about a what a given cache caches (instructions, data, etc.)

Deterministic Address Translation cache type (EDX bits 04 – 00)

Where the extended register state is stored.

What kidn of extended register state this is.

Identifies the different Hypervisor products.

Intel SGX EPC Enumeration Leaf

What type of core we have at this level in the topology (real CPU or hyper-threaded).


This table is taken from Intel manual (Section CPUID instruction).