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/*

 * FPU data structures:

 */

#ifndef _ASM_X86_FPU_H

#define _ASM_X86_FPU_H

/*

 * The legacy x87 FPU state format, as saved by FSAVE and

 * restored by the FRSTOR instructions:

 */

struct fregs_state {

	u32			cwd;	/* FPU Control Word		*/

	u32			swd;	/* FPU Status Word		*/

	u32			twd;	/* FPU Tag Word			*/

	u32			fip;	/* FPU IP Offset		*/

	u32			fcs;	/* FPU IP Selector		*/

	u32			foo;	/* FPU Operand Pointer Offset	*/

	u32			fos;	/* FPU Operand Pointer Selector	*/

	/* 8*10 bytes for each FP-reg = 80 bytes:			*/

	u32			st_space[20];

	/* Software status information [not touched by FSAVE]:		*/

	u32			status;

};

/*

 * The legacy fx SSE/MMX FPU state format, as saved by FXSAVE and

 * restored by the FXRSTOR instructions. It's similar to the FSAVE

 * format, but differs in some areas, plus has extensions at

 * the end for the XMM registers.

 */

struct fxregs_state {

	u16			cwd; /* Control Word			*/

	u16			swd; /* Status Word			*/

	u16			twd; /* Tag Word			*/

	u16			fop; /* Last Instruction Opcode		*/

	union {

		struct {

			u64	rip; /* Instruction Pointer		*/

			u64	rdp; /* Data Pointer			*/

		};

		struct {

			u32	fip; /* FPU IP Offset			*/

			u32	fcs; /* FPU IP Selector			*/

			u32	foo; /* FPU Operand Offset		*/

			u32	fos; /* FPU Operand Selector		*/

		};

	};

	u32			mxcsr;		/* MXCSR Register State */

	u32			mxcsr_mask;	/* MXCSR Mask		*/

	/* 8*16 bytes for each FP-reg = 128 bytes:			*/

	u32			st_space[32];

	/* 16*16 bytes for each XMM-reg = 256 bytes:			*/

	u32			xmm_space[64];

	u32			padding[12];

	union {

		u32		padding1[12];

		u32		sw_reserved[12];

	};

} __attribute__((aligned(16)));

/* Default value for fxregs_state.mxcsr: */

#define MXCSR_DEFAULT		0x1f80

/*

 * Software based FPU emulation state. This is arbitrary really,

 * it matches the x87 format to make it easier to understand:

 */

struct swregs_state {

	u32			cwd;

	u32			swd;

	u32			twd;

	u32			fip;

	u32			fcs;

	u32			foo;

	u32			fos;

	/* 8*10 bytes for each FP-reg = 80 bytes: */

	u32			st_space[20];

	u8			ftop;

	u8			changed;

	u8			lookahead;

	u8			no_update;

	u8			rm;

	u8			alimit;

	struct math_emu_info	*info;

	u32			entry_eip;

};

/*

 * List of XSAVE features Linux knows about:

 */

enum xfeature {

	XFEATURE_FP,

	XFEATURE_SSE,

	/*

	 * Values above here are "legacy states".

	 * Those below are "extended states".

	 */

	XFEATURE_YMM,

	XFEATURE_BNDREGS,

	XFEATURE_BNDCSR,

	XFEATURE_OPMASK,

	XFEATURE_ZMM_Hi256,

	XFEATURE_Hi16_ZMM,

	XFEATURE_MAX,

};

#define XFEATURE_MASK_FP		(1 << XFEATURE_FP)

#define XFEATURE_MASK_SSE		(1 << XFEATURE_SSE)

#define XFEATURE_MASK_YMM		(1 << XFEATURE_YMM)

#define XFEATURE_MASK_BNDREGS		(1 << XFEATURE_BNDREGS)

#define XFEATURE_MASK_BNDCSR		(1 << XFEATURE_BNDCSR)

#define XFEATURE_MASK_OPMASK		(1 << XFEATURE_OPMASK)

#define XFEATURE_MASK_ZMM_Hi256		(1 << XFEATURE_ZMM_Hi256)

#define XFEATURE_MASK_Hi16_ZMM		(1 << XFEATURE_Hi16_ZMM)

#define XFEATURE_MASK_FPSSE		(XFEATURE_MASK_FP | XFEATURE_MASK_SSE)

#define XFEATURE_MASK_AVX512		(XFEATURE_MASK_OPMASK \

					 | XFEATURE_MASK_ZMM_Hi256 \

					 | XFEATURE_MASK_Hi16_ZMM)

#define FIRST_EXTENDED_XFEATURE	XFEATURE_YMM

struct reg_128_bit {

	u8      regbytes[128/8];

};

struct reg_256_bit {

	u8	regbytes[256/8];

};

struct reg_512_bit {

	u8	regbytes[512/8];

};

/*

 * State component 2:

 *

 * There are 16x 256-bit AVX registers named YMM0-YMM15.

 * The low 128 bits are aliased to the 16 SSE registers (XMM0-XMM15)

 * and are stored in 'struct fxregs_state::xmm_space[]' in the

 * "legacy" area.

 *

 * The high 128 bits are stored here.

 */

struct ymmh_struct {

	struct reg_128_bit              hi_ymm[16];

} __packed;

/* Intel MPX support: */

struct mpx_bndreg {

	u64				lower_bound;

	u64				upper_bound;

} __packed;

/*

 * State component 3 is used for the 4 128-bit bounds registers

 */

struct mpx_bndreg_state {

	struct mpx_bndreg		bndreg[4];

} __packed;

/*

 * State component 4 is used for the 64-bit user-mode MPX

 * configuration register BNDCFGU and the 64-bit MPX status

 * register BNDSTATUS.  We call the pair "BNDCSR".

 */

struct mpx_bndcsr {

	u64				bndcfgu;

	u64				bndstatus;

} __packed;

/*

 * The BNDCSR state is padded out to be 64-bytes in size.

 */

struct mpx_bndcsr_state {

	union {

		struct mpx_bndcsr		bndcsr;

		u8				pad_to_64_bytes[64];

	};

} __packed;

/* AVX-512 Components: */

/*

 * State component 5 is used for the 8 64-bit opmask registers

 * k0-k7 (opmask state).

 */

struct avx_512_opmask_state {

	u64				opmask_reg[8];

} __packed;

/*

 * State component 6 is used for the upper 256 bits of the

 * registers ZMM0-ZMM15. These 16 256-bit values are denoted

 * ZMM0_H-ZMM15_H (ZMM_Hi256 state).

 */

struct avx_512_zmm_uppers_state {

	struct reg_256_bit		zmm_upper[16];

} __packed;

/*

 * State component 7 is used for the 16 512-bit registers

 * ZMM16-ZMM31 (Hi16_ZMM state).

 */

struct avx_512_hi16_state {

	struct reg_512_bit		hi16_zmm[16];

} __packed;

struct xstate_header {

	u64				xfeatures;

	u64				xcomp_bv;

	u64				reserved[6];

} __attribute__((packed));

/*

 * This is our most modern FPU state format, as saved by the XSAVE

 * and restored by the XRSTOR instructions.

 *

 * It consists of a legacy fxregs portion, an xstate header and

 * subsequent areas as defined by the xstate header.  Not all CPUs

 * support all the extensions, so the size of the extended area

 * can vary quite a bit between CPUs.

 */

struct xregs_state {

	struct fxregs_state		i387;

	struct xstate_header		header;

	u8				extended_state_area[0];

} __attribute__ ((packed, aligned (64)));

/*

 * This is a union of all the possible FPU state formats

 * put together, so that we can pick the right one runtime.

 *

 * The size of the structure is determined by the largest

 * member - which is the xsave area.  The padding is there

 * to ensure that statically-allocated task_structs (just

 * the init_task today) have enough space.

 */

union fpregs_state {

	struct fregs_state		fsave;

	struct fxregs_state		fxsave;

	struct swregs_state		soft;

	struct xregs_state		xsave;

	u8 __padding[PAGE_SIZE];

};

/*

 * Highest level per task FPU state data structure that

 * contains the FPU register state plus various FPU

 * state fields:

 */

struct fpu {

	/*

	 * @last_cpu:

	 *

	 * Records the last CPU on which this context was loaded into

	 * FPU registers. (In the lazy-restore case we might be

	 * able to reuse FPU registers across multiple context switches

	 * this way, if no intermediate task used the FPU.)

	 *

	 * A value of -1 is used to indicate that the FPU state in context

	 * memory is newer than the FPU state in registers, and that the

	 * FPU state should be reloaded next time the task is run.

	 */

	unsigned int			last_cpu;

	/*

	 * @fpstate_active:

	 *

	 * This flag indicates whether this context is active: if the task

	 * is not running then we can restore from this context, if the task

	 * is running then we should save into this context.

	 */

	unsigned char			fpstate_active;

	/*

	 * @fpregs_active:

	 *

	 * This flag determines whether a given context is actively

	 * loaded into the FPU's registers and that those registers

	 * represent the task's current FPU state.

	 *

	 * Note the interaction with fpstate_active:

	 *

	 *   # task does not use the FPU:

	 *   fpstate_active == 0

	 *

	 *   # task uses the FPU and regs are active:

	 *   fpstate_active == 1 && fpregs_active == 1

	 *

	 *   # the regs are inactive but still match fpstate:

	 *   fpstate_active == 1 && fpregs_active == 0 && fpregs_owner == fpu

	 *

	 * The third state is what we use for the lazy restore optimization

	 * on lazy-switching CPUs.

	 */

	unsigned char			fpregs_active;

	/*

	 * @counter:

	 *

	 * This counter contains the number of consecutive context switches

	 * during which the FPU stays used. If this is over a threshold, the

	 * lazy FPU restore logic becomes eager, to save the trap overhead.

	 * This is an unsigned char so that after 256 iterations the counter

	 * wraps and the context switch behavior turns lazy again; this is to

	 * deal with bursty apps that only use the FPU for a short time:

	 */

	unsigned char			counter;

	/*

	 * @state:

	 *

	 * In-memory copy of all FPU registers that we save/restore

	 * over context switches. If the task is using the FPU then

	 * the registers in the FPU are more recent than this state

	 * copy. If the task context-switches away then they get

	 * saved here and represent the FPU state.

	 *

	 * After context switches there may be a (short) time period

	 * during which the in-FPU hardware registers are unchanged

	 * and still perfectly match this state, if the tasks

	 * scheduled afterwards are not using the FPU.

	 *

	 * This is the 'lazy restore' window of optimization, which

	 * we track though 'fpu_fpregs_owner_ctx' and 'fpu->last_cpu'.

	 *

	 * We detect whether a subsequent task uses the FPU via setting

	 * CR0::TS to 1, which causes any FPU use to raise a #NM fault.

	 *

	 * During this window, if the task gets scheduled again, we

	 * might be able to skip having to do a restore from this

	 * memory buffer to the hardware registers - at the cost of

	 * incurring the overhead of #NM fault traps.

	 *

	 * Note that on modern CPUs that support the XSAVEOPT (or other

	 * optimized XSAVE instructions), we don't use #NM traps anymore,

	 * as the hardware can track whether FPU registers need saving

	 * or not. On such CPUs we activate the non-lazy ('eagerfpu')

	 * logic, which unconditionally saves/restores all FPU state

	 * across context switches. (if FPU state exists.)

	 */

	union fpregs_state		state;

	/*

	 * WARNING: 'state' is dynamically-sized.  Do not put

	 * anything after it here.

	 */

};

#endif /* _ASM_X86_FPU_H */