xref: /openbmc/linux/arch/x86/kvm/vmx/vmenter.S (revision f8e17c17) 
1/* SPDX-License-Identifier: GPL-2.0 */
2#include <linux/linkage.h>
3#include <asm/asm.h>
4#include <asm/bitsperlong.h>
5#include <asm/kvm_vcpu_regs.h>
6#include <asm/nospec-branch.h>
7
8#define WORD_SIZE (BITS_PER_LONG / 8)
9
10#define VCPU_RAX	__VCPU_REGS_RAX * WORD_SIZE
11#define VCPU_RCX	__VCPU_REGS_RCX * WORD_SIZE
12#define VCPU_RDX	__VCPU_REGS_RDX * WORD_SIZE
13#define VCPU_RBX	__VCPU_REGS_RBX * WORD_SIZE
14/* Intentionally omit RSP as it's context switched by hardware */
15#define VCPU_RBP	__VCPU_REGS_RBP * WORD_SIZE
16#define VCPU_RSI	__VCPU_REGS_RSI * WORD_SIZE
17#define VCPU_RDI	__VCPU_REGS_RDI * WORD_SIZE
18
19#ifdef CONFIG_X86_64
20#define VCPU_R8		__VCPU_REGS_R8  * WORD_SIZE
21#define VCPU_R9		__VCPU_REGS_R9  * WORD_SIZE
22#define VCPU_R10	__VCPU_REGS_R10 * WORD_SIZE
23#define VCPU_R11	__VCPU_REGS_R11 * WORD_SIZE
24#define VCPU_R12	__VCPU_REGS_R12 * WORD_SIZE
25#define VCPU_R13	__VCPU_REGS_R13 * WORD_SIZE
26#define VCPU_R14	__VCPU_REGS_R14 * WORD_SIZE
27#define VCPU_R15	__VCPU_REGS_R15 * WORD_SIZE
28#endif
29
30	.text
31
32/**
33 * vmx_vmenter - VM-Enter the current loaded VMCS
34 *
35 * %RFLAGS.ZF:	!VMCS.LAUNCHED, i.e. controls VMLAUNCH vs. VMRESUME
36 *
37 * Returns:
38 *	%RFLAGS.CF is set on VM-Fail Invalid
39 *	%RFLAGS.ZF is set on VM-Fail Valid
40 *	%RFLAGS.{CF,ZF} are cleared on VM-Success, i.e. VM-Exit
41 *
42 * Note that VMRESUME/VMLAUNCH fall-through and return directly if
43 * they VM-Fail, whereas a successful VM-Enter + VM-Exit will jump
44 * to vmx_vmexit.
45 */
46SYM_FUNC_START(vmx_vmenter)
47	/* EFLAGS.ZF is set if VMCS.LAUNCHED == 0 */
48	je 2f
49
501:	vmresume
51	ret
52
532:	vmlaunch
54	ret
55
563:	cmpb $0, kvm_rebooting
57	je 4f
58	ret
594:	ud2
60
61	.pushsection .fixup, "ax"
625:	jmp 3b
63	.popsection
64
65	_ASM_EXTABLE(1b, 5b)
66	_ASM_EXTABLE(2b, 5b)
67
68SYM_FUNC_END(vmx_vmenter)
69
70/**
71 * vmx_vmexit - Handle a VMX VM-Exit
72 *
73 * Returns:
74 *	%RFLAGS.{CF,ZF} are cleared on VM-Success, i.e. VM-Exit
75 *
76 * This is vmx_vmenter's partner in crime.  On a VM-Exit, control will jump
77 * here after hardware loads the host's state, i.e. this is the destination
78 * referred to by VMCS.HOST_RIP.
79 */
80SYM_FUNC_START(vmx_vmexit)
81#ifdef CONFIG_RETPOLINE
82	ALTERNATIVE "jmp .Lvmexit_skip_rsb", "", X86_FEATURE_RETPOLINE
83	/* Preserve guest's RAX, it's used to stuff the RSB. */
84	push %_ASM_AX
85
86	/* IMPORTANT: Stuff the RSB immediately after VM-Exit, before RET! */
87	FILL_RETURN_BUFFER %_ASM_AX, RSB_CLEAR_LOOPS, X86_FEATURE_RETPOLINE
88
89	pop %_ASM_AX
90.Lvmexit_skip_rsb:
91#endif
92	ret
93SYM_FUNC_END(vmx_vmexit)
94
95/**
96 * __vmx_vcpu_run - Run a vCPU via a transition to VMX guest mode
97 * @vmx:	struct vcpu_vmx * (forwarded to vmx_update_host_rsp)
98 * @regs:	unsigned long * (to guest registers)
99 * @launched:	%true if the VMCS has been launched
100 *
101 * Returns:
102 *	0 on VM-Exit, 1 on VM-Fail
103 */
104SYM_FUNC_START(__vmx_vcpu_run)
105	push %_ASM_BP
106	mov  %_ASM_SP, %_ASM_BP
107#ifdef CONFIG_X86_64
108	push %r15
109	push %r14
110	push %r13
111	push %r12
112#else
113	push %edi
114	push %esi
115#endif
116	push %_ASM_BX
117
118	/*
119	 * Save @regs, _ASM_ARG2 may be modified by vmx_update_host_rsp() and
120	 * @regs is needed after VM-Exit to save the guest's register values.
121	 */
122	push %_ASM_ARG2
123
124	/* Copy @launched to BL, _ASM_ARG3 is volatile. */
125	mov %_ASM_ARG3B, %bl
126
127	/* Adjust RSP to account for the CALL to vmx_vmenter(). */
128	lea -WORD_SIZE(%_ASM_SP), %_ASM_ARG2
129	call vmx_update_host_rsp
130
131	/* Load @regs to RAX. */
132	mov (%_ASM_SP), %_ASM_AX
133
134	/* Check if vmlaunch or vmresume is needed */
135	cmpb $0, %bl
136
137	/* Load guest registers.  Don't clobber flags. */
138	mov VCPU_RBX(%_ASM_AX), %_ASM_BX
139	mov VCPU_RCX(%_ASM_AX), %_ASM_CX
140	mov VCPU_RDX(%_ASM_AX), %_ASM_DX
141	mov VCPU_RSI(%_ASM_AX), %_ASM_SI
142	mov VCPU_RDI(%_ASM_AX), %_ASM_DI
143	mov VCPU_RBP(%_ASM_AX), %_ASM_BP
144#ifdef CONFIG_X86_64
145	mov VCPU_R8 (%_ASM_AX),  %r8
146	mov VCPU_R9 (%_ASM_AX),  %r9
147	mov VCPU_R10(%_ASM_AX), %r10
148	mov VCPU_R11(%_ASM_AX), %r11
149	mov VCPU_R12(%_ASM_AX), %r12
150	mov VCPU_R13(%_ASM_AX), %r13
151	mov VCPU_R14(%_ASM_AX), %r14
152	mov VCPU_R15(%_ASM_AX), %r15
153#endif
154	/* Load guest RAX.  This kills the @regs pointer! */
155	mov VCPU_RAX(%_ASM_AX), %_ASM_AX
156
157	/* Enter guest mode */
158	call vmx_vmenter
159
160	/* Jump on VM-Fail. */
161	jbe 2f
162
163	/* Temporarily save guest's RAX. */
164	push %_ASM_AX
165
166	/* Reload @regs to RAX. */
167	mov WORD_SIZE(%_ASM_SP), %_ASM_AX
168
169	/* Save all guest registers, including RAX from the stack */
170	__ASM_SIZE(pop) VCPU_RAX(%_ASM_AX)
171	mov %_ASM_BX,   VCPU_RBX(%_ASM_AX)
172	mov %_ASM_CX,   VCPU_RCX(%_ASM_AX)
173	mov %_ASM_DX,   VCPU_RDX(%_ASM_AX)
174	mov %_ASM_SI,   VCPU_RSI(%_ASM_AX)
175	mov %_ASM_DI,   VCPU_RDI(%_ASM_AX)
176	mov %_ASM_BP,   VCPU_RBP(%_ASM_AX)
177#ifdef CONFIG_X86_64
178	mov %r8,  VCPU_R8 (%_ASM_AX)
179	mov %r9,  VCPU_R9 (%_ASM_AX)
180	mov %r10, VCPU_R10(%_ASM_AX)
181	mov %r11, VCPU_R11(%_ASM_AX)
182	mov %r12, VCPU_R12(%_ASM_AX)
183	mov %r13, VCPU_R13(%_ASM_AX)
184	mov %r14, VCPU_R14(%_ASM_AX)
185	mov %r15, VCPU_R15(%_ASM_AX)
186#endif
187
188	/* Clear RAX to indicate VM-Exit (as opposed to VM-Fail). */
189	xor %eax, %eax
190
191	/*
192	 * Clear all general purpose registers except RSP and RAX to prevent
193	 * speculative use of the guest's values, even those that are reloaded
194	 * via the stack.  In theory, an L1 cache miss when restoring registers
195	 * could lead to speculative execution with the guest's values.
196	 * Zeroing XORs are dirt cheap, i.e. the extra paranoia is essentially
197	 * free.  RSP and RAX are exempt as RSP is restored by hardware during
198	 * VM-Exit and RAX is explicitly loaded with 0 or 1 to return VM-Fail.
199	 */
2001:	xor %ebx, %ebx
201	xor %ecx, %ecx
202	xor %edx, %edx
203	xor %esi, %esi
204	xor %edi, %edi
205	xor %ebp, %ebp
206#ifdef CONFIG_X86_64
207	xor %r8d,  %r8d
208	xor %r9d,  %r9d
209	xor %r10d, %r10d
210	xor %r11d, %r11d
211	xor %r12d, %r12d
212	xor %r13d, %r13d
213	xor %r14d, %r14d
214	xor %r15d, %r15d
215#endif
216
217	/* "POP" @regs. */
218	add $WORD_SIZE, %_ASM_SP
219	pop %_ASM_BX
220
221#ifdef CONFIG_X86_64
222	pop %r12
223	pop %r13
224	pop %r14
225	pop %r15
226#else
227	pop %esi
228	pop %edi
229#endif
230	pop %_ASM_BP
231	ret
232
233	/* VM-Fail.  Out-of-line to avoid a taken Jcc after VM-Exit. */
2342:	mov $1, %eax
235	jmp 1b
236SYM_FUNC_END(__vmx_vcpu_run)
237