summaryrefslogtreecommitdiff
path: root/arch/x86/kvm/vmx/vmenter.S
blob: 3a6461694fc2502be9d223fed57249cd0d051fe1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
/* SPDX-License-Identifier: GPL-2.0 */
#include <linux/linkage.h>
#include <asm/asm.h>
#include <asm/bitsperlong.h>
#include <asm/kvm_vcpu_regs.h>
#include <asm/nospec-branch.h>
#include <asm/segment.h>

#define WORD_SIZE (BITS_PER_LONG / 8)

#define VCPU_RAX	__VCPU_REGS_RAX * WORD_SIZE
#define VCPU_RCX	__VCPU_REGS_RCX * WORD_SIZE
#define VCPU_RDX	__VCPU_REGS_RDX * WORD_SIZE
#define VCPU_RBX	__VCPU_REGS_RBX * WORD_SIZE
/* Intentionally omit RSP as it's context switched by hardware */
#define VCPU_RBP	__VCPU_REGS_RBP * WORD_SIZE
#define VCPU_RSI	__VCPU_REGS_RSI * WORD_SIZE
#define VCPU_RDI	__VCPU_REGS_RDI * WORD_SIZE

#ifdef CONFIG_X86_64
#define VCPU_R8		__VCPU_REGS_R8  * WORD_SIZE
#define VCPU_R9		__VCPU_REGS_R9  * WORD_SIZE
#define VCPU_R10	__VCPU_REGS_R10 * WORD_SIZE
#define VCPU_R11	__VCPU_REGS_R11 * WORD_SIZE
#define VCPU_R12	__VCPU_REGS_R12 * WORD_SIZE
#define VCPU_R13	__VCPU_REGS_R13 * WORD_SIZE
#define VCPU_R14	__VCPU_REGS_R14 * WORD_SIZE
#define VCPU_R15	__VCPU_REGS_R15 * WORD_SIZE
#endif

.section .noinstr.text, "ax"

/**
 * vmx_vmenter - VM-Enter the current loaded VMCS
 *
 * %RFLAGS.ZF:	!VMCS.LAUNCHED, i.e. controls VMLAUNCH vs. VMRESUME
 *
 * Returns:
 *	%RFLAGS.CF is set on VM-Fail Invalid
 *	%RFLAGS.ZF is set on VM-Fail Valid
 *	%RFLAGS.{CF,ZF} are cleared on VM-Success, i.e. VM-Exit
 *
 * Note that VMRESUME/VMLAUNCH fall-through and return directly if
 * they VM-Fail, whereas a successful VM-Enter + VM-Exit will jump
 * to vmx_vmexit.
 */
SYM_FUNC_START_LOCAL(vmx_vmenter)
	/* EFLAGS.ZF is set if VMCS.LAUNCHED == 0 */
	je 2f

1:	vmresume
	ret

2:	vmlaunch
	ret

3:	cmpb $0, kvm_rebooting
	je 4f
	ret
4:	ud2

	_ASM_EXTABLE(1b, 3b)
	_ASM_EXTABLE(2b, 3b)

SYM_FUNC_END(vmx_vmenter)

/**
 * vmx_vmexit - Handle a VMX VM-Exit
 *
 * Returns:
 *	%RFLAGS.{CF,ZF} are cleared on VM-Success, i.e. VM-Exit
 *
 * This is vmx_vmenter's partner in crime.  On a VM-Exit, control will jump
 * here after hardware loads the host's state, i.e. this is the destination
 * referred to by VMCS.HOST_RIP.
 */
SYM_FUNC_START(vmx_vmexit)
#ifdef CONFIG_RETPOLINE
	ALTERNATIVE "jmp .Lvmexit_skip_rsb", "", X86_FEATURE_RETPOLINE
	/* Preserve guest's RAX, it's used to stuff the RSB. */
	push %_ASM_AX

	/* IMPORTANT: Stuff the RSB immediately after VM-Exit, before RET! */
	FILL_RETURN_BUFFER %_ASM_AX, RSB_CLEAR_LOOPS, X86_FEATURE_RETPOLINE

	/* Clear RFLAGS.CF and RFLAGS.ZF to preserve VM-Exit, i.e. !VM-Fail. */
	or $1, %_ASM_AX

	pop %_ASM_AX
.Lvmexit_skip_rsb:
#endif
	ret
SYM_FUNC_END(vmx_vmexit)

/**
 * __vmx_vcpu_run - Run a vCPU via a transition to VMX guest mode
 * @vmx:	struct vcpu_vmx * (forwarded to vmx_update_host_rsp)
 * @regs:	unsigned long * (to guest registers)
 * @launched:	%true if the VMCS has been launched
 *
 * Returns:
 *	0 on VM-Exit, 1 on VM-Fail
 */
SYM_FUNC_START(__vmx_vcpu_run)
	push %_ASM_BP
	mov  %_ASM_SP, %_ASM_BP
#ifdef CONFIG_X86_64
	push %r15
	push %r14
	push %r13
	push %r12
#else
	push %edi
	push %esi
#endif
	push %_ASM_BX

	/*
	 * Save @regs, _ASM_ARG2 may be modified by vmx_update_host_rsp() and
	 * @regs is needed after VM-Exit to save the guest's register values.
	 */
	push %_ASM_ARG2

	/* Copy @launched to BL, _ASM_ARG3 is volatile. */
	mov %_ASM_ARG3B, %bl

	/* Adjust RSP to account for the CALL to vmx_vmenter(). */
	lea -WORD_SIZE(%_ASM_SP), %_ASM_ARG2
	call vmx_update_host_rsp

	/* Load @regs to RAX. */
	mov (%_ASM_SP), %_ASM_AX

	/* Check if vmlaunch or vmresume is needed */
	testb %bl, %bl

	/* Load guest registers.  Don't clobber flags. */
	mov VCPU_RCX(%_ASM_AX), %_ASM_CX
	mov VCPU_RDX(%_ASM_AX), %_ASM_DX
	mov VCPU_RBX(%_ASM_AX), %_ASM_BX
	mov VCPU_RBP(%_ASM_AX), %_ASM_BP
	mov VCPU_RSI(%_ASM_AX), %_ASM_SI
	mov VCPU_RDI(%_ASM_AX), %_ASM_DI
#ifdef CONFIG_X86_64
	mov VCPU_R8 (%_ASM_AX),  %r8
	mov VCPU_R9 (%_ASM_AX),  %r9
	mov VCPU_R10(%_ASM_AX), %r10
	mov VCPU_R11(%_ASM_AX), %r11
	mov VCPU_R12(%_ASM_AX), %r12
	mov VCPU_R13(%_ASM_AX), %r13
	mov VCPU_R14(%_ASM_AX), %r14
	mov VCPU_R15(%_ASM_AX), %r15
#endif
	/* Load guest RAX.  This kills the @regs pointer! */
	mov VCPU_RAX(%_ASM_AX), %_ASM_AX

	/* Enter guest mode */
	call vmx_vmenter

	/* Jump on VM-Fail. */
	jbe 2f

	/* Temporarily save guest's RAX. */
	push %_ASM_AX

	/* Reload @regs to RAX. */
	mov WORD_SIZE(%_ASM_SP), %_ASM_AX

	/* Save all guest registers, including RAX from the stack */
	pop           VCPU_RAX(%_ASM_AX)
	mov %_ASM_CX, VCPU_RCX(%_ASM_AX)
	mov %_ASM_DX, VCPU_RDX(%_ASM_AX)
	mov %_ASM_BX, VCPU_RBX(%_ASM_AX)
	mov %_ASM_BP, VCPU_RBP(%_ASM_AX)
	mov %_ASM_SI, VCPU_RSI(%_ASM_AX)
	mov %_ASM_DI, VCPU_RDI(%_ASM_AX)
#ifdef CONFIG_X86_64
	mov %r8,  VCPU_R8 (%_ASM_AX)
	mov %r9,  VCPU_R9 (%_ASM_AX)
	mov %r10, VCPU_R10(%_ASM_AX)
	mov %r11, VCPU_R11(%_ASM_AX)
	mov %r12, VCPU_R12(%_ASM_AX)
	mov %r13, VCPU_R13(%_ASM_AX)
	mov %r14, VCPU_R14(%_ASM_AX)
	mov %r15, VCPU_R15(%_ASM_AX)
#endif

	/* Clear RAX to indicate VM-Exit (as opposed to VM-Fail). */
	xor %eax, %eax

	/*
	 * Clear all general purpose registers except RSP and RAX to prevent
	 * speculative use of the guest's values, even those that are reloaded
	 * via the stack.  In theory, an L1 cache miss when restoring registers
	 * could lead to speculative execution with the guest's values.
	 * Zeroing XORs are dirt cheap, i.e. the extra paranoia is essentially
	 * free.  RSP and RAX are exempt as RSP is restored by hardware during
	 * VM-Exit and RAX is explicitly loaded with 0 or 1 to return VM-Fail.
	 */
1:	xor %ecx, %ecx
	xor %edx, %edx
	xor %ebx, %ebx
	xor %ebp, %ebp
	xor %esi, %esi
	xor %edi, %edi
#ifdef CONFIG_X86_64
	xor %r8d,  %r8d
	xor %r9d,  %r9d
	xor %r10d, %r10d
	xor %r11d, %r11d
	xor %r12d, %r12d
	xor %r13d, %r13d
	xor %r14d, %r14d
	xor %r15d, %r15d
#endif

	/* "POP" @regs. */
	add $WORD_SIZE, %_ASM_SP
	pop %_ASM_BX

#ifdef CONFIG_X86_64
	pop %r12
	pop %r13
	pop %r14
	pop %r15
#else
	pop %esi
	pop %edi
#endif
	pop %_ASM_BP
	ret

	/* VM-Fail.  Out-of-line to avoid a taken Jcc after VM-Exit. */
2:	mov $1, %eax
	jmp 1b
SYM_FUNC_END(__vmx_vcpu_run)


.section .text, "ax"

/**
 * vmread_error_trampoline - Trampoline from inline asm to vmread_error()
 * @field:	VMCS field encoding that failed
 * @fault:	%true if the VMREAD faulted, %false if it failed

 * Save and restore volatile registers across a call to vmread_error().  Note,
 * all parameters are passed on the stack.
 */
SYM_FUNC_START(vmread_error_trampoline)
	push %_ASM_BP
	mov  %_ASM_SP, %_ASM_BP

	push %_ASM_AX
	push %_ASM_CX
	push %_ASM_DX
#ifdef CONFIG_X86_64
	push %rdi
	push %rsi
	push %r8
	push %r9
	push %r10
	push %r11
#endif
#ifdef CONFIG_X86_64
	/* Load @field and @fault to arg1 and arg2 respectively. */
	mov 3*WORD_SIZE(%rbp), %_ASM_ARG2
	mov 2*WORD_SIZE(%rbp), %_ASM_ARG1
#else
	/* Parameters are passed on the stack for 32-bit (see asmlinkage). */
	push 3*WORD_SIZE(%ebp)
	push 2*WORD_SIZE(%ebp)
#endif

	call vmread_error

#ifndef CONFIG_X86_64
	add $8, %esp
#endif

	/* Zero out @fault, which will be popped into the result register. */
	_ASM_MOV $0, 3*WORD_SIZE(%_ASM_BP)

#ifdef CONFIG_X86_64
	pop %r11
	pop %r10
	pop %r9
	pop %r8
	pop %rsi
	pop %rdi
#endif
	pop %_ASM_DX
	pop %_ASM_CX
	pop %_ASM_AX
	pop %_ASM_BP

	ret
SYM_FUNC_END(vmread_error_trampoline)

SYM_FUNC_START(vmx_do_interrupt_nmi_irqoff)
	/*
	 * Unconditionally create a stack frame, getting the correct RSP on the
	 * stack (for x86-64) would take two instructions anyways, and RBP can
	 * be used to restore RSP to make objtool happy (see below).
	 */
	push %_ASM_BP
	mov %_ASM_SP, %_ASM_BP

#ifdef CONFIG_X86_64
	/*
	 * Align RSP to a 16-byte boundary (to emulate CPU behavior) before
	 * creating the synthetic interrupt stack frame for the IRQ/NMI.
	 */
	and  $-16, %rsp
	push $__KERNEL_DS
	push %rbp
#endif
	pushf
	push $__KERNEL_CS
	CALL_NOSPEC _ASM_ARG1

	/*
	 * "Restore" RSP from RBP, even though IRET has already unwound RSP to
	 * the correct value.  objtool doesn't know the callee will IRET and,
	 * without the explicit restore, thinks the stack is getting walloped.
	 * Using an unwind hint is problematic due to x86-64's dynamic alignment.
	 */
	mov %_ASM_BP, %_ASM_SP
	pop %_ASM_BP
	ret
SYM_FUNC_END(vmx_do_interrupt_nmi_irqoff)