cpuid

package
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 Go to latest Published: Dec 29, 2021 License: Apache-2.0, MIT Imports: 6 Imported by: 0

Documentation

Overview

Package cpuid provides basic functionality for creating and adjusting CPU feature sets.

To use FeatureSets, one should start with an existing FeatureSet (either a known platform, or HostFeatureSet()) and then add, remove, and test for features as desired.

For example: on x86, test for hardware extended state saving, and if we don't have it, don't expose AVX, which cannot be saved with fxsave. 

if !HostFeatureSet().HasFeature(X86FeatureXSAVE) {
  exposedFeatures.Remove(X86FeatureAVX)
}

Index

Constants

View Source 
const (
	XSAVEFeatureX87         = 1 << 0
	XSAVEFeatureSSE         = 1 << 1
	XSAVEFeatureAVX         = 1 << 2
	XSAVEFeatureBNDREGS     = 1 << 3
	XSAVEFeatureBNDCSR      = 1 << 4
	XSAVEFeatureAVX512op    = 1 << 5
	XSAVEFeatureAVX512zmm0  = 1 << 6
	XSAVEFeatureAVX512zmm16 = 1 << 7
	XSAVEFeaturePKRU        = 1 << 9
)

These are the extended floating point state features. They are used to enumerate floating point features in XCR0, XSTATE_BV, etc.

Variables

This section is empty.

Functions

func HostID 

func HostID(axArg, cxArg uint32) (ax, bx, cx, dx uint32)

HostID executes a native CPUID instruction.

Types

type Cache 

type Cache struct {
	// Level is the hierarchical level of this cache (L1, L2, etc).
	Level uint32

	// Type is the type of cache.
	Type CacheType

	// FullyAssociative indicates that entries may be placed in any block.
	FullyAssociative bool

	// Partitions is the number of physical partitions in the cache.
	Partitions uint32

	// Ways is the number of ways of associativity in the cache.
	Ways uint32

	// Sets is the number of sets in the cache.
	Sets uint32

	// InvalidateHierarchical indicates that WBINVD/INVD from threads
	// sharing this cache acts upon lower level caches for threads sharing
	// this cache.
	InvalidateHierarchical bool

	// Inclusive indicates that this cache is inclusive of lower cache
	// levels.
	Inclusive bool

	// DirectMapped indicates that this cache is directly mapped from
	// address, rather than using a hash function.
	DirectMapped bool
}

Cache describes the parameters of a single cache on the system.

+stateify savable

type CacheType 

type CacheType uint8

CacheType describes the type of a cache, as returned in eax[4:0] for eax=4. 

const (

	// CacheData is a data cache.
	CacheData CacheType

	// CacheInstruction is an instruction cache.
	CacheInstruction

	// CacheUnified is a unified instruction and data cache.
	CacheUnified
)

type ErrIncompatible 

type ErrIncompatible struct {
	// contains filtered or unexported fields
}

ErrIncompatible is returned by FeatureSet.HostCompatible if fs is not a subset of the host feature set.

func (ErrIncompatible) Error 

func (e ErrIncompatible) Error() string

Error implements error.

type Feature 

type Feature int

Feature is a unique identifier for a particular cpu feature. We just use an int as a feature number on x86 and arm64.

On x86, features are numbered according to "blocks". Each block is 32 bits, and feature bits from the same source (cpuid leaf/level) are in the same block.

On arm64, features are numbered according to the ELF HWCAP definition. arch/arm64/include/uapi/asm/hwcap.h 

const (
	X86FeatureSSE3 Feature = iota
	X86FeaturePCLMULDQ
	X86FeatureDTES64
	X86FeatureMONITOR
	X86FeatureDSCPL
	X86FeatureVMX
	X86FeatureSMX
	X86FeatureEST
	X86FeatureTM2
	X86FeatureSSSE3 // Not a typo, "supplemental" SSE3.
	X86FeatureCNXTID
	X86FeatureSDBG
	X86FeatureFMA
	X86FeatureCX16
	X86FeatureXTPR
	X86FeaturePDCM

	X86FeaturePCID
	X86FeatureDCA
	X86FeatureSSE4_1
	X86FeatureSSE4_2
	X86FeatureX2APIC
	X86FeatureMOVBE
	X86FeaturePOPCNT
	X86FeatureTSCD
	X86FeatureAES
	X86FeatureXSAVE
	X86FeatureOSXSAVE
	X86FeatureAVX
	X86FeatureF16C
	X86FeatureRDRAND
	X86FeatureHypervisor
)

Block 0 constants are all of the "basic" feature bits returned by a cpuid in ecx with eax=1. 

const (
	X86FeatureFPU Feature = 32 + iota
	X86FeatureVME
	X86FeatureDE
	X86FeaturePSE
	X86FeatureTSC
	X86FeatureMSR
	X86FeaturePAE
	X86FeatureMCE
	X86FeatureCX8
	X86FeatureAPIC

	X86FeatureSEP
	X86FeatureMTRR
	X86FeaturePGE
	X86FeatureMCA
	X86FeatureCMOV
	X86FeaturePAT
	X86FeaturePSE36
	X86FeaturePSN
	X86FeatureCLFSH

	X86FeatureDS
	X86FeatureACPI
	X86FeatureMMX
	X86FeatureFXSR
	X86FeatureSSE
	X86FeatureSSE2
	X86FeatureSS
	X86FeatureHTT
	X86FeatureTM
	X86FeatureIA64
	X86FeaturePBE
)

Block 1 constants are all of the "basic" feature bits returned by a cpuid in edx with eax=1. 

const (
	X86FeatureFSGSBase Feature = 2*32 + iota
	X86FeatureTSC_ADJUST

	X86FeatureBMI1
	X86FeatureHLE
	X86FeatureAVX2
	X86FeatureFDP_EXCPTN_ONLY
	X86FeatureSMEP
	X86FeatureBMI2
	X86FeatureERMS
	X86FeatureINVPCID
	X86FeatureRTM
	X86FeatureCQM
	X86FeatureFPCSDS
	X86FeatureMPX
	X86FeatureRDT
	X86FeatureAVX512F
	X86FeatureAVX512DQ
	X86FeatureRDSEED
	X86FeatureADX
	X86FeatureSMAP
	X86FeatureAVX512IFMA
	X86FeaturePCOMMIT
	X86FeatureCLFLUSHOPT
	X86FeatureCLWB
	X86FeatureIPT // Intel processor trace.
	X86FeatureAVX512PF
	X86FeatureAVX512ER
	X86FeatureAVX512CD
	X86FeatureSHA
	X86FeatureAVX512BW
	X86FeatureAVX512VL
)

Block 2 bits are the "structured extended" features returned in ebx for eax=7, ecx=0. 

const (
	X86FeaturePREFETCHWT1 Feature = 3*32 + iota
	X86FeatureAVX512VBMI
	X86FeatureUMIP
	X86FeaturePKU
	X86FeatureOSPKE
	X86FeatureWAITPKG
	X86FeatureAVX512_VBMI2
	X86FeatureCET_SS
	X86FeatureGFNI
	X86FeatureVAES
	X86FeatureVPCLMULQDQ
	X86FeatureAVX512_VNNI
	X86FeatureAVX512_BITALG
	X86FeatureTME
	X86FeatureAVX512_VPOPCNTDQ

	X86FeatureLA57

	X86FeatureRDPID

	X86FeatureCLDEMOTE

	X86FeatureMOVDIRI
	X86FeatureMOVDIR64B
)

Block 3 bits are the "extended" features returned in ecx for eax=7, ecx=0. 

const (
	X86FeatureXSAVEOPT Feature = 4*32 + iota
	X86FeatureXSAVEC
	X86FeatureXGETBV1
	X86FeatureXSAVES
)

Block 4 constants are for xsave capabilities in CPUID.(EAX=0DH,ECX=01H):EAX. The CPUID leaf is available only if 'X86FeatureXSAVE' is present. 

const (
	X86FeatureLAHF64 Feature = 5*32 + iota
	X86FeatureCMP_LEGACY
	X86FeatureSVM
	X86FeatureEXTAPIC
	X86FeatureCR8_LEGACY
	X86FeatureLZCNT
	X86FeatureSSE4A
	X86FeatureMISALIGNSSE
	X86FeaturePREFETCHW
	X86FeatureOSVW
	X86FeatureIBS
	X86FeatureXOP
	X86FeatureSKINIT
	X86FeatureWDT

	X86FeatureLWP
	X86FeatureFMA4
	X86FeatureTCE

	X86FeatureTBM
	X86FeatureTOPOLOGY
	X86FeaturePERFCTR_CORE
	X86FeaturePERFCTR_NB

	X86FeatureBPEXT
	X86FeaturePERFCTR_TSC
	X86FeaturePERFCTR_LLC
	X86FeatureMWAITX
	X86FeatureADMSKEXTN
)

Block 5 constants are the extended feature bits in CPUID.(EAX=0x80000001):ECX. 

const (
	X86FeatureSYSCALL  Feature = 6*32 + 11
	X86FeatureNX       Feature = 6*32 + 20
	X86FeatureMMXEXT   Feature = 6*32 + 22
	X86FeatureFXSR_OPT Feature = 6*32 + 25
	X86FeatureGBPAGES  Feature = 6*32 + 26
	X86FeatureRDTSCP   Feature = 6*32 + 27
	X86FeatureLM       Feature = 6*32 + 29
	X86Feature3DNOWEXT Feature = 6*32 + 30
	X86Feature3DNOW    Feature = 6*32 + 31
)

Block 6 constants are the extended feature bits in CPUID.(EAX=0x80000001):EDX.

These are sparse, and so the bit positions are assigned manually.

func FeatureFromString 

func FeatureFromString(s string) (Feature, bool)

FeatureFromString returns the Feature associated with the given feature string plus a bool to indicate if it could find the feature.

func (Feature) String 

func (f Feature) String() string

String implements fmt.Stringer.

type FeatureSet 

type FeatureSet struct {
	// Set is the set of features that are enabled in this FeatureSet.
	Set map[Feature]bool

	// VendorID is the 12-char string returned in ebx:edx:ecx for eax=0.
	VendorID string

	// ExtendedFamily is part of the processor signature.
	ExtendedFamily uint8

	// ExtendedModel is part of the processor signature.
	ExtendedModel uint8

	// ProcessorType is part of the processor signature.
	ProcessorType uint8

	// Family is part of the processor signature.
	Family uint8

	// Model is part of the processor signature.
	Model uint8

	// SteppingID is part of the processor signature.
	SteppingID uint8

	// Caches describes the caches on the CPU.
	Caches []Cache

	// CacheLine is the size of a cache line in bytes.
	//
	// All caches use the same line size. This is not enforced in the CPUID
	// encoding, but is true on all known x86 processors.
	CacheLine uint32
}

FeatureSet is a set of Features for a CPU.

+stateify savable

func HostFeatureSet 

func HostFeatureSet() *FeatureSet

HostFeatureSet returns a FeatureSet that matches that of the host machine. Callers must not mutate the returned FeatureSet.

func (*FeatureSet) AMD 

func (fs *FeatureSet) AMD() bool

AMD returns true if fs describes an AMD CPU.

func (*FeatureSet) Add 

func (fs *FeatureSet) Add(feature Feature)

Add adds a Feature to a FeatureSet. It ignores duplicate features.

func (*FeatureSet) CheckHostCompatible 

func (fs *FeatureSet) CheckHostCompatible() error

CheckHostCompatible returns nil if fs is a subset of the host feature set.

func (*FeatureSet) Clone 

func (fs *FeatureSet) Clone() *FeatureSet

Clone returns a copy of fs.

func (*FeatureSet) EmulateID 

func (fs *FeatureSet) EmulateID(origAx, origCx uint32) (ax, bx, cx, dx uint32)

EmulateID emulates a cpuid instruction based on the feature set.

func (*FeatureSet) ExtendedStateSize 

func (fs *FeatureSet) ExtendedStateSize() (size, align uint)

ExtendedStateSize returns the number of bytes needed to save the "extended state" for this processor and the boundary it must be aligned to. Extended state includes floating point registers, and other cpu state that's not associated with the normal task context.

Note: We can save some space here with an optimization where we use a smaller chunk of memory depending on features that are actually enabled. Currently we just use the largest possible size for simplicity (which is about 2.5K worst case, with avx512).

func (*FeatureSet) FlagsString 

func (fs *FeatureSet) FlagsString(cpuinfoOnly bool) string

FlagsString prints out supported CPU flags. If cpuinfoOnly is true, it is equivalent to the "flags" field in /proc/cpuinfo.

func (*FeatureSet) HasFeature 

func (fs *FeatureSet) HasFeature(feature Feature) bool

HasFeature tests whether or not a feature is in the given feature set.

func (*FeatureSet) Intel 

func (fs *FeatureSet) Intel() bool

Intel returns true if fs describes an Intel CPU.

func (*FeatureSet) Remove 

func (fs *FeatureSet) Remove(feature Feature)

Remove removes a Feature from a FeatureSet. It ignores features that are not in the FeatureSet.

func (*FeatureSet) Subtract 

func (fs *FeatureSet) Subtract(other *FeatureSet) (diff map[Feature]bool)

Subtract returns the features present in fs that are not present in other. If all features in fs are present in other, Subtract returns nil.

func (*FeatureSet) UseXsave 

func (fs *FeatureSet) UseXsave() bool

UseXsave returns the choice of fp state saving instruction.

func (*FeatureSet) UseXsaveopt 

func (fs *FeatureSet) UseXsaveopt() bool

UseXsaveopt returns true if 'fs' supports the "xsaveopt" instruction.

func (*FeatureSet) ValidXCR0Mask 

func (fs *FeatureSet) ValidXCR0Mask() uint64

ValidXCR0Mask returns the bits that may be set to 1 in control register XCR0.

func (FeatureSet) WriteCPUInfoTo 

func (fs FeatureSet) WriteCPUInfoTo(cpu uint, b *bytes.Buffer)

WriteCPUInfoTo is to generate a section of one cpu in /proc/cpuinfo. This is a minimal /proc/cpuinfo, it is missing some fields like "microcode" that are not always printed in Linux. The bogomips field is simply made up.

Source Files

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