summaryrefslogtreecommitdiffstats
path: root/arch/x86/boot/compressed/mem_encrypt.S
blob: a73e4d783cae20b6786969c1505ac3bca32bedd7 (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
/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * AMD Memory Encryption Support
 *
 * Copyright (C) 2017 Advanced Micro Devices, Inc.
 *
 * Author: Tom Lendacky <thomas.lendacky@amd.com>
 */

#include <linux/linkage.h>

#include <asm/processor-flags.h>
#include <asm/msr.h>
#include <asm/asm-offsets.h>

	.text
	.code32
SYM_FUNC_START(get_sev_encryption_bit)
	xor	%eax, %eax

#ifdef CONFIG_AMD_MEM_ENCRYPT
	push	%ebx
	push	%ecx
	push	%edx

	movl	$0x80000000, %eax	/* CPUID to check the highest leaf */
	cpuid
	cmpl	$0x8000001f, %eax	/* See if 0x8000001f is available */
	jb	.Lno_sev

	/*
	 * Check for the SEV feature:
	 *   CPUID Fn8000_001F[EAX] - Bit 1
	 *   CPUID Fn8000_001F[EBX] - Bits 5:0
	 *     Pagetable bit position used to indicate encryption
	 */
	movl	$0x8000001f, %eax
	cpuid
	bt	$1, %eax		/* Check if SEV is available */
	jnc	.Lno_sev

	movl	$MSR_AMD64_SEV, %ecx	/* Read the SEV MSR */
	rdmsr
	bt	$MSR_AMD64_SEV_ENABLED_BIT, %eax	/* Check if SEV is active */
	jnc	.Lno_sev

	movl	%ebx, %eax
	andl	$0x3f, %eax		/* Return the encryption bit location */
	jmp	.Lsev_exit

.Lno_sev:
	xor	%eax, %eax

.Lsev_exit:
	pop	%edx
	pop	%ecx
	pop	%ebx

#endif	/* CONFIG_AMD_MEM_ENCRYPT */

	RET
SYM_FUNC_END(get_sev_encryption_bit)

/**
 * sev_es_req_cpuid - Request a CPUID value from the Hypervisor using
 *		      the GHCB MSR protocol
 *
 * @%eax:	Register to request (0=EAX, 1=EBX, 2=ECX, 3=EDX)
 * @%edx:	CPUID Function
 *
 * Returns 0 in %eax on success, non-zero on failure
 * %edx returns CPUID value on success
 */
SYM_CODE_START_LOCAL(sev_es_req_cpuid)
	shll	$30, %eax
	orl     $0x00000004, %eax
	movl    $MSR_AMD64_SEV_ES_GHCB, %ecx
	wrmsr
	rep; vmmcall		# VMGEXIT
	rdmsr

	/* Check response */
	movl	%eax, %ecx
	andl	$0x3ffff000, %ecx	# Bits [12-29] MBZ
	jnz	2f

	/* Check return code */
	andl    $0xfff, %eax
	cmpl    $5, %eax
	jne	2f

	/* All good - return success */
	xorl	%eax, %eax
1:
	RET
2:
	movl	$-1, %eax
	jmp	1b
SYM_CODE_END(sev_es_req_cpuid)

SYM_CODE_START(startup32_vc_handler)
	pushl	%eax
	pushl	%ebx
	pushl	%ecx
	pushl	%edx

	/* Keep CPUID function in %ebx */
	movl	%eax, %ebx

	/* Check if error-code == SVM_EXIT_CPUID */
	cmpl	$0x72, 16(%esp)
	jne	.Lfail

	movl	$0, %eax		# Request CPUID[fn].EAX
	movl	%ebx, %edx		# CPUID fn
	call	sev_es_req_cpuid	# Call helper
	testl	%eax, %eax		# Check return code
	jnz	.Lfail
	movl	%edx, 12(%esp)		# Store result

	movl	$1, %eax		# Request CPUID[fn].EBX
	movl	%ebx, %edx		# CPUID fn
	call	sev_es_req_cpuid	# Call helper
	testl	%eax, %eax		# Check return code
	jnz	.Lfail
	movl	%edx, 8(%esp)		# Store result

	movl	$2, %eax		# Request CPUID[fn].ECX
	movl	%ebx, %edx		# CPUID fn
	call	sev_es_req_cpuid	# Call helper
	testl	%eax, %eax		# Check return code
	jnz	.Lfail
	movl	%edx, 4(%esp)		# Store result

	movl	$3, %eax		# Request CPUID[fn].EDX
	movl	%ebx, %edx		# CPUID fn
	call	sev_es_req_cpuid	# Call helper
	testl	%eax, %eax		# Check return code
	jnz	.Lfail
	movl	%edx, 0(%esp)		# Store result

	/*
	 * Sanity check CPUID results from the Hypervisor. See comment in
	 * do_vc_no_ghcb() for more details on why this is necessary.
	 */

	/* Fail if SEV leaf not available in CPUID[0x80000000].EAX */
	cmpl    $0x80000000, %ebx
	jne     .Lcheck_sev
	cmpl    $0x8000001f, 12(%esp)
	jb      .Lfail
	jmp     .Ldone

.Lcheck_sev:
	/* Fail if SEV bit not set in CPUID[0x8000001f].EAX[1] */
	cmpl    $0x8000001f, %ebx
	jne     .Ldone
	btl     $1, 12(%esp)
	jnc     .Lfail

.Ldone:
	popl	%edx
	popl	%ecx
	popl	%ebx
	popl	%eax

	/* Remove error code */
	addl	$4, %esp

	/* Jump over CPUID instruction */
	addl	$2, (%esp)

	iret
.Lfail:
	/* Send terminate request to Hypervisor */
	movl    $0x100, %eax
	xorl    %edx, %edx
	movl    $MSR_AMD64_SEV_ES_GHCB, %ecx
	wrmsr
	rep; vmmcall

	/* If request fails, go to hlt loop */
	hlt
	jmp .Lfail
SYM_CODE_END(startup32_vc_handler)

	.code64

#include "../../kernel/sev_verify_cbit.S"

	.data

#ifdef CONFIG_AMD_MEM_ENCRYPT
	.balign	8
SYM_DATA(sme_me_mask,		.quad 0)
SYM_DATA(sev_status,		.quad 0)
SYM_DATA(sev_check_data,	.quad 0)
#endif