1 /* 2 * FPU data structures: 3 */ 4 #ifndef _ASM_X86_FPU_H 5 #define _ASM_X86_FPU_H 6 7 /* 8 * The legacy x87 FPU state format, as saved by FSAVE and 9 * restored by the FRSTOR instructions: 10 */ 11 struct fregs_state { 12 u32 cwd; /* FPU Control Word */ 13 u32 swd; /* FPU Status Word */ 14 u32 twd; /* FPU Tag Word */ 15 u32 fip; /* FPU IP Offset */ 16 u32 fcs; /* FPU IP Selector */ 17 u32 foo; /* FPU Operand Pointer Offset */ 18 u32 fos; /* FPU Operand Pointer Selector */ 19 20 /* 8*10 bytes for each FP-reg = 80 bytes: */ 21 u32 st_space[20]; 22 23 /* Software status information [not touched by FSAVE]: */ 24 u32 status; 25 }; 26 27 /* 28 * The legacy fx SSE/MMX FPU state format, as saved by FXSAVE and 29 * restored by the FXRSTOR instructions. It's similar to the FSAVE 30 * format, but differs in some areas, plus has extensions at 31 * the end for the XMM registers. 32 */ 33 struct fxregs_state { 34 u16 cwd; /* Control Word */ 35 u16 swd; /* Status Word */ 36 u16 twd; /* Tag Word */ 37 u16 fop; /* Last Instruction Opcode */ 38 union { 39 struct { 40 u64 rip; /* Instruction Pointer */ 41 u64 rdp; /* Data Pointer */ 42 }; 43 struct { 44 u32 fip; /* FPU IP Offset */ 45 u32 fcs; /* FPU IP Selector */ 46 u32 foo; /* FPU Operand Offset */ 47 u32 fos; /* FPU Operand Selector */ 48 }; 49 }; 50 u32 mxcsr; /* MXCSR Register State */ 51 u32 mxcsr_mask; /* MXCSR Mask */ 52 53 /* 8*16 bytes for each FP-reg = 128 bytes: */ 54 u32 st_space[32]; 55 56 /* 16*16 bytes for each XMM-reg = 256 bytes: */ 57 u32 xmm_space[64]; 58 59 u32 padding[12]; 60 61 union { 62 u32 padding1[12]; 63 u32 sw_reserved[12]; 64 }; 65 66 } __attribute__((aligned(16))); 67 68 /* Default value for fxregs_state.mxcsr: */ 69 #define MXCSR_DEFAULT 0x1f80 70 71 /* 72 * Software based FPU emulation state. This is arbitrary really, 73 * it matches the x87 format to make it easier to understand: 74 */ 75 struct swregs_state { 76 u32 cwd; 77 u32 swd; 78 u32 twd; 79 u32 fip; 80 u32 fcs; 81 u32 foo; 82 u32 fos; 83 /* 8*10 bytes for each FP-reg = 80 bytes: */ 84 u32 st_space[20]; 85 u8 ftop; 86 u8 changed; 87 u8 lookahead; 88 u8 no_update; 89 u8 rm; 90 u8 alimit; 91 struct math_emu_info *info; 92 u32 entry_eip; 93 }; 94 95 /* 96 * List of XSAVE features Linux knows about: 97 */ 98 enum xfeature { 99 XFEATURE_FP, 100 XFEATURE_SSE, 101 /* 102 * Values above here are "legacy states". 103 * Those below are "extended states". 104 */ 105 XFEATURE_YMM, 106 XFEATURE_BNDREGS, 107 XFEATURE_BNDCSR, 108 XFEATURE_OPMASK, 109 XFEATURE_ZMM_Hi256, 110 XFEATURE_Hi16_ZMM, 111 112 XFEATURE_MAX, 113 }; 114 115 #define XFEATURE_MASK_FP (1 << XFEATURE_FP) 116 #define XFEATURE_MASK_SSE (1 << XFEATURE_SSE) 117 #define XFEATURE_MASK_YMM (1 << XFEATURE_YMM) 118 #define XFEATURE_MASK_BNDREGS (1 << XFEATURE_BNDREGS) 119 #define XFEATURE_MASK_BNDCSR (1 << XFEATURE_BNDCSR) 120 #define XFEATURE_MASK_OPMASK (1 << XFEATURE_OPMASK) 121 #define XFEATURE_MASK_ZMM_Hi256 (1 << XFEATURE_ZMM_Hi256) 122 #define XFEATURE_MASK_Hi16_ZMM (1 << XFEATURE_Hi16_ZMM) 123 124 #define XFEATURE_MASK_FPSSE (XFEATURE_MASK_FP | XFEATURE_MASK_SSE) 125 #define XFEATURE_MASK_AVX512 (XFEATURE_MASK_OPMASK \ 126 | XFEATURE_MASK_ZMM_Hi256 \ 127 | XFEATURE_MASK_Hi16_ZMM) 128 129 #define FIRST_EXTENDED_XFEATURE XFEATURE_YMM 130 131 struct reg_128_bit { 132 u8 regbytes[128/8]; 133 }; 134 struct reg_256_bit { 135 u8 regbytes[256/8]; 136 }; 137 struct reg_512_bit { 138 u8 regbytes[512/8]; 139 }; 140 141 /* 142 * State component 2: 143 * 144 * There are 16x 256-bit AVX registers named YMM0-YMM15. 145 * The low 128 bits are aliased to the 16 SSE registers (XMM0-XMM15) 146 * and are stored in 'struct fxregs_state::xmm_space[]' in the 147 * "legacy" area. 148 * 149 * The high 128 bits are stored here. 150 */ 151 struct ymmh_struct { 152 struct reg_128_bit hi_ymm[16]; 153 } __packed; 154 155 /* Intel MPX support: */ 156 157 struct mpx_bndreg { 158 u64 lower_bound; 159 u64 upper_bound; 160 } __packed; 161 /* 162 * State component 3 is used for the 4 128-bit bounds registers 163 */ 164 struct mpx_bndreg_state { 165 struct mpx_bndreg bndreg[4]; 166 } __packed; 167 168 /* 169 * State component 4 is used for the 64-bit user-mode MPX 170 * configuration register BNDCFGU and the 64-bit MPX status 171 * register BNDSTATUS. We call the pair "BNDCSR". 172 */ 173 struct mpx_bndcsr { 174 u64 bndcfgu; 175 u64 bndstatus; 176 } __packed; 177 178 /* 179 * The BNDCSR state is padded out to be 64-bytes in size. 180 */ 181 struct mpx_bndcsr_state { 182 union { 183 struct mpx_bndcsr bndcsr; 184 u8 pad_to_64_bytes[64]; 185 }; 186 } __packed; 187 188 /* AVX-512 Components: */ 189 190 /* 191 * State component 5 is used for the 8 64-bit opmask registers 192 * k0-k7 (opmask state). 193 */ 194 struct avx_512_opmask_state { 195 u64 opmask_reg[8]; 196 } __packed; 197 198 /* 199 * State component 6 is used for the upper 256 bits of the 200 * registers ZMM0-ZMM15. These 16 256-bit values are denoted 201 * ZMM0_H-ZMM15_H (ZMM_Hi256 state). 202 */ 203 struct avx_512_zmm_uppers_state { 204 struct reg_256_bit zmm_upper[16]; 205 } __packed; 206 207 /* 208 * State component 7 is used for the 16 512-bit registers 209 * ZMM16-ZMM31 (Hi16_ZMM state). 210 */ 211 struct avx_512_hi16_state { 212 struct reg_512_bit hi16_zmm[16]; 213 } __packed; 214 215 struct xstate_header { 216 u64 xfeatures; 217 u64 xcomp_bv; 218 u64 reserved[6]; 219 } __attribute__((packed)); 220 221 /* 222 * This is our most modern FPU state format, as saved by the XSAVE 223 * and restored by the XRSTOR instructions. 224 * 225 * It consists of a legacy fxregs portion, an xstate header and 226 * subsequent areas as defined by the xstate header. Not all CPUs 227 * support all the extensions, so the size of the extended area 228 * can vary quite a bit between CPUs. 229 */ 230 struct xregs_state { 231 struct fxregs_state i387; 232 struct xstate_header header; 233 u8 extended_state_area[0]; 234 } __attribute__ ((packed, aligned (64))); 235 236 /* 237 * This is a union of all the possible FPU state formats 238 * put together, so that we can pick the right one runtime. 239 * 240 * The size of the structure is determined by the largest 241 * member - which is the xsave area. The padding is there 242 * to ensure that statically-allocated task_structs (just 243 * the init_task today) have enough space. 244 */ 245 union fpregs_state { 246 struct fregs_state fsave; 247 struct fxregs_state fxsave; 248 struct swregs_state soft; 249 struct xregs_state xsave; 250 u8 __padding[PAGE_SIZE]; 251 }; 252 253 /* 254 * Highest level per task FPU state data structure that 255 * contains the FPU register state plus various FPU 256 * state fields: 257 */ 258 struct fpu { 259 /* 260 * @last_cpu: 261 * 262 * Records the last CPU on which this context was loaded into 263 * FPU registers. (In the lazy-restore case we might be 264 * able to reuse FPU registers across multiple context switches 265 * this way, if no intermediate task used the FPU.) 266 * 267 * A value of -1 is used to indicate that the FPU state in context 268 * memory is newer than the FPU state in registers, and that the 269 * FPU state should be reloaded next time the task is run. 270 */ 271 unsigned int last_cpu; 272 273 /* 274 * @fpstate_active: 275 * 276 * This flag indicates whether this context is active: if the task 277 * is not running then we can restore from this context, if the task 278 * is running then we should save into this context. 279 */ 280 unsigned char fpstate_active; 281 282 /* 283 * @fpregs_active: 284 * 285 * This flag determines whether a given context is actively 286 * loaded into the FPU's registers and that those registers 287 * represent the task's current FPU state. 288 * 289 * Note the interaction with fpstate_active: 290 * 291 * # task does not use the FPU: 292 * fpstate_active == 0 293 * 294 * # task uses the FPU and regs are active: 295 * fpstate_active == 1 && fpregs_active == 1 296 * 297 * # the regs are inactive but still match fpstate: 298 * fpstate_active == 1 && fpregs_active == 0 && fpregs_owner == fpu 299 * 300 * The third state is what we use for the lazy restore optimization 301 * on lazy-switching CPUs. 302 */ 303 unsigned char fpregs_active; 304 305 /* 306 * @counter: 307 * 308 * This counter contains the number of consecutive context switches 309 * during which the FPU stays used. If this is over a threshold, the 310 * lazy FPU restore logic becomes eager, to save the trap overhead. 311 * This is an unsigned char so that after 256 iterations the counter 312 * wraps and the context switch behavior turns lazy again; this is to 313 * deal with bursty apps that only use the FPU for a short time: 314 */ 315 unsigned char counter; 316 /* 317 * @state: 318 * 319 * In-memory copy of all FPU registers that we save/restore 320 * over context switches. If the task is using the FPU then 321 * the registers in the FPU are more recent than this state 322 * copy. If the task context-switches away then they get 323 * saved here and represent the FPU state. 324 * 325 * After context switches there may be a (short) time period 326 * during which the in-FPU hardware registers are unchanged 327 * and still perfectly match this state, if the tasks 328 * scheduled afterwards are not using the FPU. 329 * 330 * This is the 'lazy restore' window of optimization, which 331 * we track though 'fpu_fpregs_owner_ctx' and 'fpu->last_cpu'. 332 * 333 * We detect whether a subsequent task uses the FPU via setting 334 * CR0::TS to 1, which causes any FPU use to raise a #NM fault. 335 * 336 * During this window, if the task gets scheduled again, we 337 * might be able to skip having to do a restore from this 338 * memory buffer to the hardware registers - at the cost of 339 * incurring the overhead of #NM fault traps. 340 * 341 * Note that on modern CPUs that support the XSAVEOPT (or other 342 * optimized XSAVE instructions), we don't use #NM traps anymore, 343 * as the hardware can track whether FPU registers need saving 344 * or not. On such CPUs we activate the non-lazy ('eagerfpu') 345 * logic, which unconditionally saves/restores all FPU state 346 * across context switches. (if FPU state exists.) 347 */ 348 union fpregs_state state; 349 /* 350 * WARNING: 'state' is dynamically-sized. Do not put 351 * anything after it here. 352 */ 353 }; 354 355 #endif /* _ASM_X86_FPU_H */ 356