xref: /linux/arch/x86/kvm/kvm_emulate.h (revision c532de5a67a70f8533d495f8f2aaa9a0491c3ad0)
1 /* SPDX-License-Identifier: GPL-2.0 */
2 /******************************************************************************
3  * x86_emulate.h
4  *
5  * Generic x86 (32-bit and 64-bit) instruction decoder and emulator.
6  *
7  * Copyright (c) 2005 Keir Fraser
8  *
9  * From: xen-unstable 10676:af9809f51f81a3c43f276f00c81a52ef558afda4
10  */
11 
12 #ifndef _ASM_X86_KVM_X86_EMULATE_H
13 #define _ASM_X86_KVM_X86_EMULATE_H
14 
15 #include <asm/desc_defs.h>
16 #include "fpu.h"
17 
18 struct x86_emulate_ctxt;
19 enum x86_intercept;
20 enum x86_intercept_stage;
21 
22 struct x86_exception {
23 	u8 vector;
24 	bool error_code_valid;
25 	u16 error_code;
26 	bool nested_page_fault;
27 	u64 address; /* cr2 or nested page fault gpa */
28 	u8 async_page_fault;
29 	unsigned long exit_qualification;
30 };
31 
32 /*
33  * This struct is used to carry enough information from the instruction
34  * decoder to main KVM so that a decision can be made whether the
35  * instruction needs to be intercepted or not.
36  */
37 struct x86_instruction_info {
38 	u8  intercept;          /* which intercept                      */
39 	u8  rep_prefix;         /* rep prefix?                          */
40 	u8  modrm_mod;		/* mod part of modrm			*/
41 	u8  modrm_reg;          /* index of register used               */
42 	u8  modrm_rm;		/* rm part of modrm			*/
43 	u64 src_val;            /* value of source operand              */
44 	u64 dst_val;            /* value of destination operand         */
45 	u8  src_bytes;          /* size of source operand               */
46 	u8  dst_bytes;          /* size of destination operand          */
47 	u8  ad_bytes;           /* size of src/dst address              */
48 	u64 next_rip;           /* rip following the instruction        */
49 };
50 
51 /*
52  * x86_emulate_ops:
53  *
54  * These operations represent the instruction emulator's interface to memory.
55  * There are two categories of operation: those that act on ordinary memory
56  * regions (*_std), and those that act on memory regions known to require
57  * special treatment or emulation (*_emulated).
58  *
59  * The emulator assumes that an instruction accesses only one 'emulated memory'
60  * location, that this location is the given linear faulting address (cr2), and
61  * that this is one of the instruction's data operands. Instruction fetches and
62  * stack operations are assumed never to access emulated memory. The emulator
63  * automatically deduces which operand of a string-move operation is accessing
64  * emulated memory, and assumes that the other operand accesses normal memory.
65  *
66  * NOTES:
67  *  1. The emulator isn't very smart about emulated vs. standard memory.
68  *     'Emulated memory' access addresses should be checked for sanity.
69  *     'Normal memory' accesses may fault, and the caller must arrange to
70  *     detect and handle reentrancy into the emulator via recursive faults.
71  *     Accesses may be unaligned and may cross page boundaries.
72  *  2. If the access fails (cannot emulate, or a standard access faults) then
73  *     it is up to the memop to propagate the fault to the guest VM via
74  *     some out-of-band mechanism, unknown to the emulator. The memop signals
75  *     failure by returning X86EMUL_PROPAGATE_FAULT to the emulator, which will
76  *     then immediately bail.
77  *  3. Valid access sizes are 1, 2, 4 and 8 bytes. On x86/32 systems only
78  *     cmpxchg8b_emulated need support 8-byte accesses.
79  *  4. The emulator cannot handle 64-bit mode emulation on an x86/32 system.
80  */
81 /* Access completed successfully: continue emulation as normal. */
82 #define X86EMUL_CONTINUE        0
83 /* Access is unhandleable: bail from emulation and return error to caller. */
84 #define X86EMUL_UNHANDLEABLE    1
85 /* Terminate emulation but return success to the caller. */
86 #define X86EMUL_PROPAGATE_FAULT 2 /* propagate a generated fault to guest */
87 #define X86EMUL_RETRY_INSTR     3 /* retry the instruction for some reason */
88 #define X86EMUL_CMPXCHG_FAILED  4 /* cmpxchg did not see expected value */
89 #define X86EMUL_IO_NEEDED       5 /* IO is needed to complete emulation */
90 #define X86EMUL_INTERCEPTED     6 /* Intercepted by nested VMCB/VMCS */
91 
92 /* x86-specific emulation flags */
93 #define X86EMUL_F_WRITE			BIT(0)
94 #define X86EMUL_F_FETCH			BIT(1)
95 #define X86EMUL_F_IMPLICIT		BIT(2)
96 #define X86EMUL_F_INVLPG		BIT(3)
97 
98 struct x86_emulate_ops {
99 	void (*vm_bugged)(struct x86_emulate_ctxt *ctxt);
100 	/*
101 	 * read_gpr: read a general purpose register (rax - r15)
102 	 *
103 	 * @reg: gpr number.
104 	 */
105 	ulong (*read_gpr)(struct x86_emulate_ctxt *ctxt, unsigned reg);
106 	/*
107 	 * write_gpr: write a general purpose register (rax - r15)
108 	 *
109 	 * @reg: gpr number.
110 	 * @val: value to write.
111 	 */
112 	void (*write_gpr)(struct x86_emulate_ctxt *ctxt, unsigned reg, ulong val);
113 	/*
114 	 * read_std: Read bytes of standard (non-emulated/special) memory.
115 	 *           Used for descriptor reading.
116 	 *  @addr:  [IN ] Linear address from which to read.
117 	 *  @val:   [OUT] Value read from memory, zero-extended to 'u_long'.
118 	 *  @bytes: [IN ] Number of bytes to read from memory.
119 	 *  @system:[IN ] Whether the access is forced to be at CPL0.
120 	 */
121 	int (*read_std)(struct x86_emulate_ctxt *ctxt,
122 			unsigned long addr, void *val,
123 			unsigned int bytes,
124 			struct x86_exception *fault, bool system);
125 
126 	/*
127 	 * write_std: Write bytes of standard (non-emulated/special) memory.
128 	 *            Used for descriptor writing.
129 	 *  @addr:  [IN ] Linear address to which to write.
130 	 *  @val:   [OUT] Value write to memory, zero-extended to 'u_long'.
131 	 *  @bytes: [IN ] Number of bytes to write to memory.
132 	 *  @system:[IN ] Whether the access is forced to be at CPL0.
133 	 */
134 	int (*write_std)(struct x86_emulate_ctxt *ctxt,
135 			 unsigned long addr, void *val, unsigned int bytes,
136 			 struct x86_exception *fault, bool system);
137 	/*
138 	 * fetch: Read bytes of standard (non-emulated/special) memory.
139 	 *        Used for instruction fetch.
140 	 *  @addr:  [IN ] Linear address from which to read.
141 	 *  @val:   [OUT] Value read from memory, zero-extended to 'u_long'.
142 	 *  @bytes: [IN ] Number of bytes to read from memory.
143 	 */
144 	int (*fetch)(struct x86_emulate_ctxt *ctxt,
145 		     unsigned long addr, void *val, unsigned int bytes,
146 		     struct x86_exception *fault);
147 
148 	/*
149 	 * read_emulated: Read bytes from emulated/special memory area.
150 	 *  @addr:  [IN ] Linear address from which to read.
151 	 *  @val:   [OUT] Value read from memory, zero-extended to 'u_long'.
152 	 *  @bytes: [IN ] Number of bytes to read from memory.
153 	 */
154 	int (*read_emulated)(struct x86_emulate_ctxt *ctxt,
155 			     unsigned long addr, void *val, unsigned int bytes,
156 			     struct x86_exception *fault);
157 
158 	/*
159 	 * write_emulated: Write bytes to emulated/special memory area.
160 	 *  @addr:  [IN ] Linear address to which to write.
161 	 *  @val:   [IN ] Value to write to memory (low-order bytes used as
162 	 *                required).
163 	 *  @bytes: [IN ] Number of bytes to write to memory.
164 	 */
165 	int (*write_emulated)(struct x86_emulate_ctxt *ctxt,
166 			      unsigned long addr, const void *val,
167 			      unsigned int bytes,
168 			      struct x86_exception *fault);
169 
170 	/*
171 	 * cmpxchg_emulated: Emulate an atomic (LOCKed) CMPXCHG operation on an
172 	 *                   emulated/special memory area.
173 	 *  @addr:  [IN ] Linear address to access.
174 	 *  @old:   [IN ] Value expected to be current at @addr.
175 	 *  @new:   [IN ] Value to write to @addr.
176 	 *  @bytes: [IN ] Number of bytes to access using CMPXCHG.
177 	 */
178 	int (*cmpxchg_emulated)(struct x86_emulate_ctxt *ctxt,
179 				unsigned long addr,
180 				const void *old,
181 				const void *new,
182 				unsigned int bytes,
183 				struct x86_exception *fault);
184 	void (*invlpg)(struct x86_emulate_ctxt *ctxt, ulong addr);
185 
186 	int (*pio_in_emulated)(struct x86_emulate_ctxt *ctxt,
187 			       int size, unsigned short port, void *val,
188 			       unsigned int count);
189 
190 	int (*pio_out_emulated)(struct x86_emulate_ctxt *ctxt,
191 				int size, unsigned short port, const void *val,
192 				unsigned int count);
193 
194 	bool (*get_segment)(struct x86_emulate_ctxt *ctxt, u16 *selector,
195 			    struct desc_struct *desc, u32 *base3, int seg);
196 	void (*set_segment)(struct x86_emulate_ctxt *ctxt, u16 selector,
197 			    struct desc_struct *desc, u32 base3, int seg);
198 	unsigned long (*get_cached_segment_base)(struct x86_emulate_ctxt *ctxt,
199 						 int seg);
200 	void (*get_gdt)(struct x86_emulate_ctxt *ctxt, struct desc_ptr *dt);
201 	void (*get_idt)(struct x86_emulate_ctxt *ctxt, struct desc_ptr *dt);
202 	void (*set_gdt)(struct x86_emulate_ctxt *ctxt, struct desc_ptr *dt);
203 	void (*set_idt)(struct x86_emulate_ctxt *ctxt, struct desc_ptr *dt);
204 	ulong (*get_cr)(struct x86_emulate_ctxt *ctxt, int cr);
205 	int (*set_cr)(struct x86_emulate_ctxt *ctxt, int cr, ulong val);
206 	int (*cpl)(struct x86_emulate_ctxt *ctxt);
207 	ulong (*get_dr)(struct x86_emulate_ctxt *ctxt, int dr);
208 	int (*set_dr)(struct x86_emulate_ctxt *ctxt, int dr, ulong value);
209 	int (*set_msr_with_filter)(struct x86_emulate_ctxt *ctxt, u32 msr_index, u64 data);
210 	int (*get_msr_with_filter)(struct x86_emulate_ctxt *ctxt, u32 msr_index, u64 *pdata);
211 	int (*get_msr)(struct x86_emulate_ctxt *ctxt, u32 msr_index, u64 *pdata);
212 	int (*check_rdpmc_early)(struct x86_emulate_ctxt *ctxt, u32 pmc);
213 	int (*read_pmc)(struct x86_emulate_ctxt *ctxt, u32 pmc, u64 *pdata);
214 	void (*halt)(struct x86_emulate_ctxt *ctxt);
215 	void (*wbinvd)(struct x86_emulate_ctxt *ctxt);
216 	int (*fix_hypercall)(struct x86_emulate_ctxt *ctxt);
217 	int (*intercept)(struct x86_emulate_ctxt *ctxt,
218 			 struct x86_instruction_info *info,
219 			 enum x86_intercept_stage stage);
220 
221 	bool (*get_cpuid)(struct x86_emulate_ctxt *ctxt, u32 *eax, u32 *ebx,
222 			  u32 *ecx, u32 *edx, bool exact_only);
223 	bool (*guest_has_movbe)(struct x86_emulate_ctxt *ctxt);
224 	bool (*guest_has_fxsr)(struct x86_emulate_ctxt *ctxt);
225 	bool (*guest_has_rdpid)(struct x86_emulate_ctxt *ctxt);
226 	bool (*guest_cpuid_is_intel_compatible)(struct x86_emulate_ctxt *ctxt);
227 
228 	void (*set_nmi_mask)(struct x86_emulate_ctxt *ctxt, bool masked);
229 
230 	bool (*is_smm)(struct x86_emulate_ctxt *ctxt);
231 	bool (*is_guest_mode)(struct x86_emulate_ctxt *ctxt);
232 	int (*leave_smm)(struct x86_emulate_ctxt *ctxt);
233 	void (*triple_fault)(struct x86_emulate_ctxt *ctxt);
234 	int (*set_xcr)(struct x86_emulate_ctxt *ctxt, u32 index, u64 xcr);
235 
236 	gva_t (*get_untagged_addr)(struct x86_emulate_ctxt *ctxt, gva_t addr,
237 				   unsigned int flags);
238 };
239 
240 /* Type, address-of, and value of an instruction's operand. */
241 struct operand {
242 	enum { OP_REG, OP_MEM, OP_MEM_STR, OP_IMM, OP_XMM, OP_MM, OP_NONE } type;
243 	unsigned int bytes;
244 	unsigned int count;
245 	union {
246 		unsigned long orig_val;
247 		u64 orig_val64;
248 	};
249 	union {
250 		unsigned long *reg;
251 		struct segmented_address {
252 			ulong ea;
253 			unsigned seg;
254 		} mem;
255 		unsigned xmm;
256 		unsigned mm;
257 	} addr;
258 	union {
259 		unsigned long val;
260 		u64 val64;
261 		char valptr[sizeof(sse128_t)];
262 		sse128_t vec_val;
263 		u64 mm_val;
264 		void *data;
265 	};
266 };
267 
268 struct fetch_cache {
269 	u8 data[15];
270 	u8 *ptr;
271 	u8 *end;
272 };
273 
274 struct read_cache {
275 	u8 data[1024];
276 	unsigned long pos;
277 	unsigned long end;
278 };
279 
280 /* Execution mode, passed to the emulator. */
281 enum x86emul_mode {
282 	X86EMUL_MODE_REAL,	/* Real mode.             */
283 	X86EMUL_MODE_VM86,	/* Virtual 8086 mode.     */
284 	X86EMUL_MODE_PROT16,	/* 16-bit protected mode. */
285 	X86EMUL_MODE_PROT32,	/* 32-bit protected mode. */
286 	X86EMUL_MODE_PROT64,	/* 64-bit (long) mode.    */
287 };
288 
289 /*
290  * fastop functions are declared as taking a never-defined fastop parameter,
291  * so they can't be called from C directly.
292  */
293 struct fastop;
294 
295 typedef void (*fastop_t)(struct fastop *);
296 
297 /*
298  * The emulator's _regs array tracks only the GPRs, i.e. excludes RIP.  RIP is
299  * tracked/accessed via _eip, and except for RIP relative addressing, which
300  * also uses _eip, RIP cannot be a register operand nor can it be an operand in
301  * a ModRM or SIB byte.
302  */
303 #ifdef CONFIG_X86_64
304 #define NR_EMULATOR_GPRS	16
305 #else
306 #define NR_EMULATOR_GPRS	8
307 #endif
308 
309 struct x86_emulate_ctxt {
310 	void *vcpu;
311 	const struct x86_emulate_ops *ops;
312 
313 	/* Register state before/after emulation. */
314 	unsigned long eflags;
315 	unsigned long eip; /* eip before instruction emulation */
316 	/* Emulated execution mode, represented by an X86EMUL_MODE value. */
317 	enum x86emul_mode mode;
318 
319 	/* interruptibility state, as a result of execution of STI or MOV SS */
320 	int interruptibility;
321 
322 	bool perm_ok; /* do not check permissions if true */
323 	bool tf;	/* TF value before instruction (after for syscall/sysret) */
324 
325 	bool have_exception;
326 	struct x86_exception exception;
327 
328 	/* GPA available */
329 	bool gpa_available;
330 	gpa_t gpa_val;
331 
332 	/*
333 	 * decode cache
334 	 */
335 
336 	/* current opcode length in bytes */
337 	u8 opcode_len;
338 	u8 b;
339 	u8 intercept;
340 	u8 op_bytes;
341 	u8 ad_bytes;
342 	union {
343 		int (*execute)(struct x86_emulate_ctxt *ctxt);
344 		fastop_t fop;
345 	};
346 	int (*check_perm)(struct x86_emulate_ctxt *ctxt);
347 
348 	bool rip_relative;
349 	u8 rex_prefix;
350 	u8 lock_prefix;
351 	u8 rep_prefix;
352 	/* bitmaps of registers in _regs[] that can be read */
353 	u16 regs_valid;
354 	/* bitmaps of registers in _regs[] that have been written */
355 	u16 regs_dirty;
356 	/* modrm */
357 	u8 modrm;
358 	u8 modrm_mod;
359 	u8 modrm_reg;
360 	u8 modrm_rm;
361 	u8 modrm_seg;
362 	u8 seg_override;
363 	u64 d;
364 	unsigned long _eip;
365 
366 	/* Here begins the usercopy section. */
367 	struct operand src;
368 	struct operand src2;
369 	struct operand dst;
370 	struct operand memop;
371 	unsigned long _regs[NR_EMULATOR_GPRS];
372 	struct operand *memopp;
373 	struct fetch_cache fetch;
374 	struct read_cache io_read;
375 	struct read_cache mem_read;
376 	bool is_branch;
377 };
378 
379 #define KVM_EMULATOR_BUG_ON(cond, ctxt)		\
380 ({						\
381 	int __ret = (cond);			\
382 						\
383 	if (WARN_ON_ONCE(__ret))		\
384 		ctxt->ops->vm_bugged(ctxt);	\
385 	unlikely(__ret);			\
386 })
387 
388 /* Repeat String Operation Prefix */
389 #define REPE_PREFIX	0xf3
390 #define REPNE_PREFIX	0xf2
391 
392 /* CPUID vendors */
393 #define X86EMUL_CPUID_VENDOR_AuthenticAMD_ebx 0x68747541
394 #define X86EMUL_CPUID_VENDOR_AuthenticAMD_ecx 0x444d4163
395 #define X86EMUL_CPUID_VENDOR_AuthenticAMD_edx 0x69746e65
396 
397 #define X86EMUL_CPUID_VENDOR_AMDisbetterI_ebx 0x69444d41
398 #define X86EMUL_CPUID_VENDOR_AMDisbetterI_ecx 0x21726574
399 #define X86EMUL_CPUID_VENDOR_AMDisbetterI_edx 0x74656273
400 
401 #define X86EMUL_CPUID_VENDOR_HygonGenuine_ebx 0x6f677948
402 #define X86EMUL_CPUID_VENDOR_HygonGenuine_ecx 0x656e6975
403 #define X86EMUL_CPUID_VENDOR_HygonGenuine_edx 0x6e65476e
404 
405 #define X86EMUL_CPUID_VENDOR_GenuineIntel_ebx 0x756e6547
406 #define X86EMUL_CPUID_VENDOR_GenuineIntel_ecx 0x6c65746e
407 #define X86EMUL_CPUID_VENDOR_GenuineIntel_edx 0x49656e69
408 
409 #define X86EMUL_CPUID_VENDOR_CentaurHauls_ebx 0x746e6543
410 #define X86EMUL_CPUID_VENDOR_CentaurHauls_ecx 0x736c7561
411 #define X86EMUL_CPUID_VENDOR_CentaurHauls_edx 0x48727561
412 
413 static inline bool is_guest_vendor_intel(u32 ebx, u32 ecx, u32 edx)
414 {
415 	return ebx == X86EMUL_CPUID_VENDOR_GenuineIntel_ebx &&
416 	       ecx == X86EMUL_CPUID_VENDOR_GenuineIntel_ecx &&
417 	       edx == X86EMUL_CPUID_VENDOR_GenuineIntel_edx;
418 }
419 
420 static inline bool is_guest_vendor_amd(u32 ebx, u32 ecx, u32 edx)
421 {
422 	return (ebx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ebx &&
423 		ecx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ecx &&
424 		edx == X86EMUL_CPUID_VENDOR_AuthenticAMD_edx) ||
425 	       (ebx == X86EMUL_CPUID_VENDOR_AMDisbetterI_ebx &&
426 		ecx == X86EMUL_CPUID_VENDOR_AMDisbetterI_ecx &&
427 		edx == X86EMUL_CPUID_VENDOR_AMDisbetterI_edx);
428 }
429 
430 static inline bool is_guest_vendor_hygon(u32 ebx, u32 ecx, u32 edx)
431 {
432 	return ebx == X86EMUL_CPUID_VENDOR_HygonGenuine_ebx &&
433 	       ecx == X86EMUL_CPUID_VENDOR_HygonGenuine_ecx &&
434 	       edx == X86EMUL_CPUID_VENDOR_HygonGenuine_edx;
435 }
436 
437 enum x86_intercept_stage {
438 	X86_ICTP_NONE = 0,   /* Allow zero-init to not match anything */
439 	X86_ICPT_PRE_EXCEPT,
440 	X86_ICPT_POST_EXCEPT,
441 	X86_ICPT_POST_MEMACCESS,
442 };
443 
444 enum x86_intercept {
445 	x86_intercept_none,
446 	x86_intercept_cr_read,
447 	x86_intercept_cr_write,
448 	x86_intercept_clts,
449 	x86_intercept_lmsw,
450 	x86_intercept_smsw,
451 	x86_intercept_dr_read,
452 	x86_intercept_dr_write,
453 	x86_intercept_lidt,
454 	x86_intercept_sidt,
455 	x86_intercept_lgdt,
456 	x86_intercept_sgdt,
457 	x86_intercept_lldt,
458 	x86_intercept_sldt,
459 	x86_intercept_ltr,
460 	x86_intercept_str,
461 	x86_intercept_rdtsc,
462 	x86_intercept_rdpmc,
463 	x86_intercept_pushf,
464 	x86_intercept_popf,
465 	x86_intercept_cpuid,
466 	x86_intercept_rsm,
467 	x86_intercept_iret,
468 	x86_intercept_intn,
469 	x86_intercept_invd,
470 	x86_intercept_pause,
471 	x86_intercept_hlt,
472 	x86_intercept_invlpg,
473 	x86_intercept_invlpga,
474 	x86_intercept_vmrun,
475 	x86_intercept_vmload,
476 	x86_intercept_vmsave,
477 	x86_intercept_vmmcall,
478 	x86_intercept_stgi,
479 	x86_intercept_clgi,
480 	x86_intercept_skinit,
481 	x86_intercept_rdtscp,
482 	x86_intercept_rdpid,
483 	x86_intercept_icebp,
484 	x86_intercept_wbinvd,
485 	x86_intercept_monitor,
486 	x86_intercept_mwait,
487 	x86_intercept_rdmsr,
488 	x86_intercept_wrmsr,
489 	x86_intercept_in,
490 	x86_intercept_ins,
491 	x86_intercept_out,
492 	x86_intercept_outs,
493 	x86_intercept_xsetbv,
494 
495 	nr_x86_intercepts
496 };
497 
498 /* Host execution mode. */
499 #if defined(CONFIG_X86_32)
500 #define X86EMUL_MODE_HOST X86EMUL_MODE_PROT32
501 #elif defined(CONFIG_X86_64)
502 #define X86EMUL_MODE_HOST X86EMUL_MODE_PROT64
503 #endif
504 
505 int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int emulation_type);
506 bool x86_page_table_writing_insn(struct x86_emulate_ctxt *ctxt);
507 #define EMULATION_FAILED -1
508 #define EMULATION_OK 0
509 #define EMULATION_RESTART 1
510 #define EMULATION_INTERCEPTED 2
511 void init_decode_cache(struct x86_emulate_ctxt *ctxt);
512 int x86_emulate_insn(struct x86_emulate_ctxt *ctxt);
513 int emulator_task_switch(struct x86_emulate_ctxt *ctxt,
514 			 u16 tss_selector, int idt_index, int reason,
515 			 bool has_error_code, u32 error_code);
516 int emulate_int_real(struct x86_emulate_ctxt *ctxt, int irq);
517 void emulator_invalidate_register_cache(struct x86_emulate_ctxt *ctxt);
518 void emulator_writeback_register_cache(struct x86_emulate_ctxt *ctxt);
519 bool emulator_can_use_gpa(struct x86_emulate_ctxt *ctxt);
520 
521 static inline ulong reg_read(struct x86_emulate_ctxt *ctxt, unsigned nr)
522 {
523 	if (KVM_EMULATOR_BUG_ON(nr >= NR_EMULATOR_GPRS, ctxt))
524 		nr &= NR_EMULATOR_GPRS - 1;
525 
526 	if (!(ctxt->regs_valid & (1 << nr))) {
527 		ctxt->regs_valid |= 1 << nr;
528 		ctxt->_regs[nr] = ctxt->ops->read_gpr(ctxt, nr);
529 	}
530 	return ctxt->_regs[nr];
531 }
532 
533 static inline ulong *reg_write(struct x86_emulate_ctxt *ctxt, unsigned nr)
534 {
535 	if (KVM_EMULATOR_BUG_ON(nr >= NR_EMULATOR_GPRS, ctxt))
536 		nr &= NR_EMULATOR_GPRS - 1;
537 
538 	BUILD_BUG_ON(sizeof(ctxt->regs_dirty) * BITS_PER_BYTE < NR_EMULATOR_GPRS);
539 	BUILD_BUG_ON(sizeof(ctxt->regs_valid) * BITS_PER_BYTE < NR_EMULATOR_GPRS);
540 
541 	ctxt->regs_valid |= 1 << nr;
542 	ctxt->regs_dirty |= 1 << nr;
543 	return &ctxt->_regs[nr];
544 }
545 
546 static inline ulong *reg_rmw(struct x86_emulate_ctxt *ctxt, unsigned nr)
547 {
548 	reg_read(ctxt, nr);
549 	return reg_write(ctxt, nr);
550 }
551 
552 #endif /* _ASM_X86_KVM_X86_EMULATE_H */
553