I'm assuming that the "32" inference comes from these lines:
/* AMD-defined CPU features, CPUID level 0x80000008 (ebx), word 13 */
#define X86_FEATURE_CLZERO (13*32+0) /* CLZERO instruction */
+#define X86_FEATURE_IRPERF (13*32+1) /* Instructions Retired Count */
The assumption is that there are 32 cores based on what I presume is the
size of a zeroed cacheline no, I should have indicated a memory offset for the cacheline (CL) ZERO feature, this is an instruction and the number 13 is the offset, while 32 appears to be a hardcoded size. Each "feature" appears to occupy one byte in a 32 byte chunk, and it looks like there is a coding convention where sets of features are described as X*32 + Y where X is an integer chunk of 32 bytes (starting at 0) and Y is an offset within that 32 byte range. For example, CLZERO is at 13*32 + 0, and a new performance counter instruction that is added in that patch gets put in next door at 13*32 + 1. However, 32, has nothing to do with the core count. See the larger code snippet from the kernel below.Well, I found some other patches that might throw this into conflict:
/* Intel-defined CPU QoS Sub-leaf, CPUID level 0x0000000F:1 (edx), word 12 */
#define X86_FEATURE_CQM_OCCUP_LLC (12*32+ 0) /* LLC occupancy monitoring if 1 */
+/* AMD-defined CPU features, CPUID level 0x80000008 (ebx), word 13 */
+#define X86_FEATURE_CLZERO (13*32+0) /* CLZERO instruction */
Looks like Intel is coming out with 32 core CPUs too! Or the number 32, which is you know, 2
5 and is incredibly common in many many programming constructs, might not directly correlate to the number of cores.
Edit: In fact, let's take it a step further. Note how that macro begins with "X86_FEATURE"? Well there's a whole .h file in the kernel that is chock full of different X86_FEATURE macros. Have a look:
http://lxr.free-electrons.com/source/ar ... ufeature.hI'm copying the relevant bit below, notice the gratuitous use of "32" and no, these aren't all some AMD-specific core count numbers:
/* Intel-defined CPU features, CPUID level 0x00000001 (edx), word 0 */
25 #define X86_FEATURE_FPU ( 0*32+ 0) /* Onboard FPU */
26 #define X86_FEATURE_VME ( 0*32+ 1) /* Virtual Mode Extensions */
27 #define X86_FEATURE_DE ( 0*32+ 2) /* Debugging Extensions */
28 #define X86_FEATURE_PSE ( 0*32+ 3) /* Page Size Extensions */
29 #define X86_FEATURE_TSC ( 0*32+ 4) /* Time Stamp Counter */
30 #define X86_FEATURE_MSR ( 0*32+ 5) /* Model-Specific Registers */
31 #define X86_FEATURE_PAE ( 0*32+ 6) /* Physical Address Extensions */
32 #define X86_FEATURE_MCE ( 0*32+ 7) /* Machine Check Exception */
33 #define X86_FEATURE_CX8 ( 0*32+ 8) /* CMPXCHG8 instruction */
34 #define X86_FEATURE_APIC ( 0*32+ 9) /* Onboard APIC */
35 #define X86_FEATURE_SEP ( 0*32+11) /* SYSENTER/SYSEXIT */
36 #define X86_FEATURE_MTRR ( 0*32+12) /* Memory Type Range Registers */
37 #define X86_FEATURE_PGE ( 0*32+13) /* Page Global Enable */
38 #define X86_FEATURE_MCA ( 0*32+14) /* Machine Check Architecture */
39 #define X86_FEATURE_CMOV ( 0*32+15) /* CMOV instructions */
40 /* (plus FCMOVcc, FCOMI with FPU) */
41 #define X86_FEATURE_PAT ( 0*32+16) /* Page Attribute Table */
42 #define X86_FEATURE_PSE36 ( 0*32+17) /* 36-bit PSEs */
43 #define X86_FEATURE_PN ( 0*32+18) /* Processor serial number */
44 #define X86_FEATURE_CLFLUSH ( 0*32+19) /* CLFLUSH instruction */
45 #define X86_FEATURE_DS ( 0*32+21) /* "dts" Debug Store */
46 #define X86_FEATURE_ACPI ( 0*32+22) /* ACPI via MSR */
47 #define X86_FEATURE_MMX ( 0*32+23) /* Multimedia Extensions */
48 #define X86_FEATURE_FXSR ( 0*32+24) /* FXSAVE/FXRSTOR, CR4.OSFXSR */
49 #define X86_FEATURE_XMM ( 0*32+25) /* "sse" */
50 #define X86_FEATURE_XMM2 ( 0*32+26) /* "sse2" */
51 #define X86_FEATURE_SELFSNOOP ( 0*32+27) /* "ss" CPU self snoop */
52 #define X86_FEATURE_HT ( 0*32+28) /* Hyper-Threading */
53 #define X86_FEATURE_ACC ( 0*32+29) /* "tm" Automatic clock control */
54 #define X86_FEATURE_IA64 ( 0*32+30) /* IA-64 processor */
55 #define X86_FEATURE_PBE ( 0*32+31) /* Pending Break Enable */
56
57 /* AMD-defined CPU features, CPUID level 0x80000001, word 1 */
58 /* Don't duplicate feature flags which are redundant with Intel! */
59 #define X86_FEATURE_SYSCALL ( 1*32+11) /* SYSCALL/SYSRET */
60 #define X86_FEATURE_MP ( 1*32+19) /* MP Capable. */
61 #define X86_FEATURE_NX ( 1*32+20) /* Execute Disable */
62 #define X86_FEATURE_MMXEXT ( 1*32+22) /* AMD MMX extensions */
63 #define X86_FEATURE_FXSR_OPT ( 1*32+25) /* FXSAVE/FXRSTOR optimizations */
64 #define X86_FEATURE_GBPAGES ( 1*32+26) /* "pdpe1gb" GB pages */
65 #define X86_FEATURE_RDTSCP ( 1*32+27) /* RDTSCP */
66 #define X86_FEATURE_LM ( 1*32+29) /* Long Mode (x86-64) */
67 #define X86_FEATURE_3DNOWEXT ( 1*32+30) /* AMD 3DNow! extensions */
68 #define X86_FEATURE_3DNOW ( 1*32+31) /* 3DNow! */
69
70 /* Transmeta-defined CPU features, CPUID level 0x80860001, word 2 */
71 #define X86_FEATURE_RECOVERY ( 2*32+ 0) /* CPU in recovery mode */
72 #define X86_FEATURE_LONGRUN ( 2*32+ 1) /* Longrun power control */
73 #define X86_FEATURE_LRTI ( 2*32+ 3) /* LongRun table interface */
74
75 /* Other features, Linux-defined mapping, word 3 */
76 /* This range is used for feature bits which conflict or are synthesized */
77 #define X86_FEATURE_CXMMX ( 3*32+ 0) /* Cyrix MMX extensions */
78 #define X86_FEATURE_K6_MTRR ( 3*32+ 1) /* AMD K6 nonstandard MTRRs */
79 #define X86_FEATURE_CYRIX_ARR ( 3*32+ 2) /* Cyrix ARRs (= MTRRs) */
80 #define X86_FEATURE_CENTAUR_MCR ( 3*32+ 3) /* Centaur MCRs (= MTRRs) */
81 /* cpu types for specific tunings: */
82 #define X86_FEATURE_K8 ( 3*32+ 4) /* "" Opteron, Athlon64 */
83 #define X86_FEATURE_K7 ( 3*32+ 5) /* "" Athlon */
84 #define X86_FEATURE_P3 ( 3*32+ 6) /* "" P3 */
85 #define X86_FEATURE_P4 ( 3*32+ 7) /* "" P4 */
86 #define X86_FEATURE_CONSTANT_TSC ( 3*32+ 8) /* TSC ticks at a constant rate */
87 #define X86_FEATURE_UP ( 3*32+ 9) /* smp kernel running on up */
88 /* free, was #define X86_FEATURE_FXSAVE_LEAK ( 3*32+10) * "" FXSAVE leaks FOP/FIP/FOP */
89 #define X86_FEATURE_ARCH_PERFMON ( 3*32+11) /* Intel Architectural PerfMon */
90 #define X86_FEATURE_PEBS ( 3*32+12) /* Precise-Event Based Sampling */
91 #define X86_FEATURE_BTS ( 3*32+13) /* Branch Trace Store */
92 #define X86_FEATURE_SYSCALL32 ( 3*32+14) /* "" syscall in ia32 userspace */
93 #define X86_FEATURE_SYSENTER32 ( 3*32+15) /* "" sysenter in ia32 userspace */
94 #define X86_FEATURE_REP_GOOD ( 3*32+16) /* rep microcode works well */
95 #define X86_FEATURE_MFENCE_RDTSC ( 3*32+17) /* "" Mfence synchronizes RDTSC */
96 #define X86_FEATURE_LFENCE_RDTSC ( 3*32+18) /* "" Lfence synchronizes RDTSC */
97 /* free, was #define X86_FEATURE_11AP ( 3*32+19) * "" Bad local APIC aka 11AP */
98 #define X86_FEATURE_NOPL ( 3*32+20) /* The NOPL (0F 1F) instructions */
99 #define X86_FEATURE_ALWAYS ( 3*32+21) /* "" Always-present feature */
100 #define X86_FEATURE_XTOPOLOGY ( 3*32+22) /* cpu topology enum extensions */
101 #define X86_FEATURE_TSC_RELIABLE ( 3*32+23) /* TSC is known to be reliable */
102 #define X86_FEATURE_NONSTOP_TSC ( 3*32+24) /* TSC does not stop in C states */
103 /* free, was #define X86_FEATURE_CLFLUSH_MONITOR ( 3*32+25) * "" clflush reqd with monitor */
104 #define X86_FEATURE_EXTD_APICID ( 3*32+26) /* has extended APICID (8 bits) */
105 #define X86_FEATURE_AMD_DCM ( 3*32+27) /* multi-node processor */
106 #define X86_FEATURE_APERFMPERF ( 3*32+28) /* APERFMPERF */
107 #define X86_FEATURE_EAGER_FPU ( 3*32+29) /* "eagerfpu" Non lazy FPU restore */
108 #define X86_FEATURE_NONSTOP_TSC_S3 ( 3*32+30) /* TSC doesn't stop in S3 state */
109
110 /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */
111 #define X86_FEATURE_XMM3 ( 4*32+ 0) /* "pni" SSE-3 */
112 #define X86_FEATURE_PCLMULQDQ ( 4*32+ 1) /* PCLMULQDQ instruction */
113 #define X86_FEATURE_DTES64 ( 4*32+ 2) /* 64-bit Debug Store */
114 #define X86_FEATURE_MWAIT ( 4*32+ 3) /* "monitor" Monitor/Mwait support */
115 #define X86_FEATURE_DSCPL ( 4*32+ 4) /* "ds_cpl" CPL Qual. Debug Store */
116 #define X86_FEATURE_VMX ( 4*32+ 5) /* Hardware virtualization */
117 #define X86_FEATURE_SMX ( 4*32+ 6) /* Safer mode */
118 #define X86_FEATURE_EST ( 4*32+ 7) /* Enhanced SpeedStep */
119 #define X86_FEATURE_TM2 ( 4*32+ 8) /* Thermal Monitor 2 */
120 #define X86_FEATURE_SSSE3 ( 4*32+ 9) /* Supplemental SSE-3 */
121 #define X86_FEATURE_CID ( 4*32+10) /* Context ID */
122 #define X86_FEATURE_SDBG ( 4*32+11) /* Silicon Debug */
123 #define X86_FEATURE_FMA ( 4*32+12) /* Fused multiply-add */
124 #define X86_FEATURE_CX16 ( 4*32+13) /* CMPXCHG16B */
125 #define X86_FEATURE_XTPR ( 4*32+14) /* Send Task Priority Messages */
126 #define X86_FEATURE_PDCM ( 4*32+15) /* Performance Capabilities */
127 #define X86_FEATURE_PCID ( 4*32+17) /* Process Context Identifiers */
128 #define X86_FEATURE_DCA ( 4*32+18) /* Direct Cache Access */
129 #define X86_FEATURE_XMM4_1 ( 4*32+19) /* "sse4_1" SSE-4.1 */
130 #define X86_FEATURE_XMM4_2 ( 4*32+20) /* "sse4_2" SSE-4.2 */
131 #define X86_FEATURE_X2APIC ( 4*32+21) /* x2APIC */
132 #define X86_FEATURE_MOVBE ( 4*32+22) /* MOVBE instruction */
133 #define X86_FEATURE_POPCNT ( 4*32+23) /* POPCNT instruction */
134 #define X86_FEATURE_TSC_DEADLINE_TIMER ( 4*32+24) /* Tsc deadline timer */
135 #define X86_FEATURE_AES ( 4*32+25) /* AES instructions */
136 #define X86_FEATURE_XSAVE ( 4*32+26) /* XSAVE/XRSTOR/XSETBV/XGETBV */
137 #define X86_FEATURE_OSXSAVE ( 4*32+27) /* "" XSAVE enabled in the OS */
138 #define X86_FEATURE_AVX ( 4*32+28) /* Advanced Vector Extensions */
139 #define X86_FEATURE_F16C ( 4*32+29) /* 16-bit fp conversions */
140 #define X86_FEATURE_RDRAND ( 4*32+30) /* The RDRAND instruction */
141 #define X86_FEATURE_HYPERVISOR ( 4*32+31) /* Running on a hypervisor */
142
143 /* VIA/Cyrix/Centaur-defined CPU features, CPUID level 0xC0000001, word 5 */
144 #define X86_FEATURE_XSTORE ( 5*32+ 2) /* "rng" RNG present (xstore) */
145 #define X86_FEATURE_XSTORE_EN ( 5*32+ 3) /* "rng_en" RNG enabled */
146 #define X86_FEATURE_XCRYPT ( 5*32+ 6) /* "ace" on-CPU crypto (xcrypt) */
147 #define X86_FEATURE_XCRYPT_EN ( 5*32+ 7) /* "ace_en" on-CPU crypto enabled */
148 #define X86_FEATURE_ACE2 ( 5*32+ 8) /* Advanced Cryptography Engine v2 */
149 #define X86_FEATURE_ACE2_EN ( 5*32+ 9) /* ACE v2 enabled */
150 #define X86_FEATURE_PHE ( 5*32+10) /* PadLock Hash Engine */
151 #define X86_FEATURE_PHE_EN ( 5*32+11) /* PHE enabled */
152 #define X86_FEATURE_PMM ( 5*32+12) /* PadLock Montgomery Multiplier */
153 #define X86_FEATURE_PMM_EN ( 5*32+13) /* PMM enabled */
154
155 /* More extended AMD flags: CPUID level 0x80000001, ecx, word 6 */
156 #define X86_FEATURE_LAHF_LM ( 6*32+ 0) /* LAHF/SAHF in long mode */
157 #define X86_FEATURE_CMP_LEGACY ( 6*32+ 1) /* If yes HyperThreading not valid */
158 #define X86_FEATURE_SVM ( 6*32+ 2) /* Secure virtual machine */
159 #define X86_FEATURE_EXTAPIC ( 6*32+ 3) /* Extended APIC space */
160 #define X86_FEATURE_CR8_LEGACY ( 6*32+ 4) /* CR8 in 32-bit mode */
161 #define X86_FEATURE_ABM ( 6*32+ 5) /* Advanced bit manipulation */
162 #define X86_FEATURE_SSE4A ( 6*32+ 6) /* SSE-4A */
163 #define X86_FEATURE_MISALIGNSSE ( 6*32+ 7) /* Misaligned SSE mode */
164 #define X86_FEATURE_3DNOWPREFETCH ( 6*32+ 8) /* 3DNow prefetch instructions */
165 #define X86_FEATURE_OSVW ( 6*32+ 9) /* OS Visible Workaround */
166 #define X86_FEATURE_IBS ( 6*32+10) /* Instruction Based Sampling */
167 #define X86_FEATURE_XOP ( 6*32+11) /* extended AVX instructions */
168 #define X86_FEATURE_SKINIT ( 6*32+12) /* SKINIT/STGI instructions */
169 #define X86_FEATURE_WDT ( 6*32+13) /* Watchdog timer */
170 #define X86_FEATURE_LWP ( 6*32+15) /* Light Weight Profiling */
171 #define X86_FEATURE_FMA4 ( 6*32+16) /* 4 operands MAC instructions */
172 #define X86_FEATURE_TCE ( 6*32+17) /* translation cache extension */
173 #define X86_FEATURE_NODEID_MSR ( 6*32+19) /* NodeId MSR */
174 #define X86_FEATURE_TBM ( 6*32+21) /* trailing bit manipulations */
175 #define X86_FEATURE_TOPOEXT ( 6*32+22) /* topology extensions CPUID leafs */
176 #define X86_FEATURE_PERFCTR_CORE ( 6*32+23) /* core performance counter extensions */
177 #define X86_FEATURE_PERFCTR_NB ( 6*32+24) /* NB performance counter extensions */
178 #define X86_FEATURE_BPEXT (6*32+26) /* data breakpoint extension */
179 #define X86_FEATURE_PERFCTR_L2 ( 6*32+28) /* L2 performance counter extensions */
180 #define X86_FEATURE_MWAITX ( 6*32+29) /* MWAIT extension (MONITORX/MWAITX) */
181
182 /*
183 * Auxiliary flags: Linux defined - For features scattered in various
184 * CPUID levels like 0x6, 0xA etc, word 7
185 */
186 #define X86_FEATURE_IDA ( 7*32+ 0) /* Intel Dynamic Acceleration */
187 #define X86_FEATURE_ARAT ( 7*32+ 1) /* Always Running APIC Timer */
188 #define X86_FEATURE_CPB ( 7*32+ 2) /* AMD Core Performance Boost */
189 #define X86_FEATURE_EPB ( 7*32+ 3) /* IA32_ENERGY_PERF_BIAS support */
190 #define X86_FEATURE_PLN ( 7*32+ 5) /* Intel Power Limit Notification */
191 #define X86_FEATURE_PTS ( 7*32+ 6) /* Intel Package Thermal Status */
192 #define X86_FEATURE_DTHERM ( 7*32+ 7) /* Digital Thermal Sensor */
193 #define X86_FEATURE_HW_PSTATE ( 7*32+ 8) /* AMD HW-PState */
194 #define X86_FEATURE_PROC_FEEDBACK ( 7*32+ 9) /* AMD ProcFeedbackInterface */
195 #define X86_FEATURE_HWP ( 7*32+ 10) /* "hwp" Intel HWP */
196 #define X86_FEATURE_HWP_NOTIFY ( 7*32+ 11) /* Intel HWP_NOTIFY */
197 #define X86_FEATURE_HWP_ACT_WINDOW ( 7*32+ 12) /* Intel HWP_ACT_WINDOW */
198 #define X86_FEATURE_HWP_EPP ( 7*32+13) /* Intel HWP_EPP */
199 #define X86_FEATURE_HWP_PKG_REQ ( 7*32+14) /* Intel HWP_PKG_REQ */
200 #define X86_FEATURE_INTEL_PT ( 7*32+15) /* Intel Processor Trace */
201
202 /* Virtualization flags: Linux defined, word 8 */
203 #define X86_FEATURE_TPR_SHADOW ( 8*32+ 0) /* Intel TPR Shadow */
204 #define X86_FEATURE_VNMI ( 8*32+ 1) /* Intel Virtual NMI */
205 #define X86_FEATURE_FLEXPRIORITY ( 8*32+ 2) /* Intel FlexPriority */
206 #define X86_FEATURE_EPT ( 8*32+ 3) /* Intel Extended Page Table */
207 #define X86_FEATURE_VPID ( 8*32+ 4) /* Intel Virtual Processor ID */
208 #define X86_FEATURE_NPT ( 8*32+ 5) /* AMD Nested Page Table support */
209 #define X86_FEATURE_LBRV ( 8*32+ 6) /* AMD LBR Virtualization support */
210 #define X86_FEATURE_SVML ( 8*32+ 7) /* "svm_lock" AMD SVM locking MSR */
211 #define X86_FEATURE_NRIPS ( 8*32+ 8) /* "nrip_save" AMD SVM next_rip save */
212 #define X86_FEATURE_TSCRATEMSR ( 8*32+ 9) /* "tsc_scale" AMD TSC scaling support */
213 #define X86_FEATURE_VMCBCLEAN ( 8*32+10) /* "vmcb_clean" AMD VMCB clean bits support */
214 #define X86_FEATURE_FLUSHBYASID ( 8*32+11) /* AMD flush-by-ASID support */
215 #define X86_FEATURE_DECODEASSISTS ( 8*32+12) /* AMD Decode Assists support */
216 #define X86_FEATURE_PAUSEFILTER ( 8*32+13) /* AMD filtered pause intercept */
217 #define X86_FEATURE_PFTHRESHOLD ( 8*32+14) /* AMD pause filter threshold */
218 #define X86_FEATURE_VMMCALL ( 8*32+15) /* Prefer vmmcall to vmcall */
219 #define X86_FEATURE_XENPV ( 8*32+16) /* "" Xen paravirtual guest */
220
221
222 /* Intel-defined CPU features, CPUID level 0x00000007:0 (ebx), word 9 */
223 #define X86_FEATURE_FSGSBASE ( 9*32+ 0) /* {RD/WR}{FS/GS}BASE instructions*/
224 #define X86_FEATURE_TSC_ADJUST ( 9*32+ 1) /* TSC adjustment MSR 0x3b */
225 #define X86_FEATURE_BMI1 ( 9*32+ 3) /* 1st group bit manipulation extensions */
226 #define X86_FEATURE_HLE ( 9*32+ 4) /* Hardware Lock Elision */
227 #define X86_FEATURE_AVX2 ( 9*32+ 5) /* AVX2 instructions */
228 #define X86_FEATURE_SMEP ( 9*32+ 7) /* Supervisor Mode Execution Protection */
229 #define X86_FEATURE_BMI2 ( 9*32+ 8) /* 2nd group bit manipulation extensions */
230 #define X86_FEATURE_ERMS ( 9*32+ 9) /* Enhanced REP MOVSB/STOSB */
231 #define X86_FEATURE_INVPCID ( 9*32+10) /* Invalidate Processor Context ID */
232 #define X86_FEATURE_RTM ( 9*32+11) /* Restricted Transactional Memory */
233 #define X86_FEATURE_CQM ( 9*32+12) /* Cache QoS Monitoring */
234 #define X86_FEATURE_MPX ( 9*32+14) /* Memory Protection Extension */
235 #define X86_FEATURE_AVX512F ( 9*32+16) /* AVX-512 Foundation */
236 #define X86_FEATURE_RDSEED ( 9*32+18) /* The RDSEED instruction */
237 #define X86_FEATURE_ADX ( 9*32+19) /* The ADCX and ADOX instructions */
238 #define X86_FEATURE_SMAP ( 9*32+20) /* Supervisor Mode Access Prevention */
239 #define X86_FEATURE_PCOMMIT ( 9*32+22) /* PCOMMIT instruction */
240 #define X86_FEATURE_CLFLUSHOPT ( 9*32+23) /* CLFLUSHOPT instruction */
241 #define X86_FEATURE_CLWB ( 9*32+24) /* CLWB instruction */
242 #define X86_FEATURE_AVX512PF ( 9*32+26) /* AVX-512 Prefetch */
243 #define X86_FEATURE_AVX512ER ( 9*32+27) /* AVX-512 Exponential and Reciprocal */
244 #define X86_FEATURE_AVX512CD ( 9*32+28) /* AVX-512 Conflict Detection */
245 #define X86_FEATURE_SHA_NI ( 9*32+29) /* SHA1/SHA256 Instruction Extensions */
246
247 /* Extended state features, CPUID level 0x0000000d:1 (eax), word 10 */
248 #define X86_FEATURE_XSAVEOPT (10*32+ 0) /* XSAVEOPT */
249 #define X86_FEATURE_XSAVEC (10*32+ 1) /* XSAVEC */
250 #define X86_FEATURE_XGETBV1 (10*32+ 2) /* XGETBV with ECX = 1 */
251 #define X86_FEATURE_XSAVES (10*32+ 3) /* XSAVES/XRSTORS */
252
253 /* Intel-defined CPU QoS Sub-leaf, CPUID level 0x0000000F:0 (edx), word 11 */
254 #define X86_FEATURE_CQM_LLC (11*32+ 1) /* LLC QoS if 1 */
255
256 /* Intel-defined CPU QoS Sub-leaf, CPUID level 0x0000000F:1 (edx), word 12 */
257 #define X86_FEATURE_CQM_OCCUP_LLC (12*32+ 0) /* LLC occupancy monitoring if 1 */
258
259 /* AMD-defined CPU features, CPUID level 0x80000008 (ebx), word 13 */
260 #define X86_FEATURE_CLZERO (13*32+0) /* CLZERO instruction */