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1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 *
4 * verify_cpu.S - Code for cpu long mode and SSE verification. This
5 * code has been borrowed from boot/setup.S and was introduced by
6 * Andi Kleen.
7 *
8 * Copyright (c) 2007 Andi Kleen (ak@suse.de)
9 * Copyright (c) 2007 Eric Biederman (ebiederm@xmission.com)
10 * Copyright (c) 2007 Vivek Goyal (vgoyal@in.ibm.com)
11 * Copyright (c) 2010 Kees Cook (kees.cook@canonical.com)
12 *
13 * This is a common code for verification whether CPU supports
14 * long mode and SSE or not. It is not called directly instead this
15 * file is included at various places and compiled in that context.
16 * This file is expected to run in 32bit code. Currently:
17 *
18 * arch/x86/boot/compressed/head_64.S: Boot cpu verification
19 * arch/x86/kernel/trampoline_64.S: secondary processor verification
20 * arch/x86/kernel/head_32.S: processor startup
21 *
22 * verify_cpu, returns the status of longmode and SSE in register %eax.
23 * 0: Success 1: Failure
24 *
25 * On Intel, the XD_DISABLE flag will be cleared as a side-effect.
26 *
27 * The caller needs to check for the error code and take the action
28 * appropriately. Either display a message or halt.
29 */
30
31#include <asm/cpufeatures.h>
32#include <asm/cpufeaturemasks.h>
33#include <asm/msr-index.h>
34
35#define SSE_MASK \
36 (REQUIRED_MASK0 & ((1<<(X86_FEATURE_XMM & 31)) | (1<<(X86_FEATURE_XMM2 & 31))))
37
38SYM_FUNC_START_LOCAL(verify_cpu)
39 pushf # Save caller passed flags
40 push $0 # Kill any dangerous flags
41 popf
42
43#ifndef __x86_64__
44 pushfl # standard way to check for cpuid
45 popl %eax
46 movl %eax,%ebx
47 xorl $0x200000,%eax
48 pushl %eax
49 popfl
50 pushfl
51 popl %eax
52 cmpl %eax,%ebx
53 jz .Lverify_cpu_no_longmode # cpu has no cpuid
54#endif
55
56 movl $0x0,%eax # See if cpuid 1 is implemented
57 cpuid
58 cmpl $0x1,%eax
59 jb .Lverify_cpu_no_longmode # no cpuid 1
60
61 xor %di,%di
62 cmpl $0x68747541,%ebx # AuthenticAMD
63 jnz .Lverify_cpu_noamd
64 cmpl $0x69746e65,%edx
65 jnz .Lverify_cpu_noamd
66 cmpl $0x444d4163,%ecx
67 jnz .Lverify_cpu_noamd
68 mov $1,%di # cpu is from AMD
69 jmp .Lverify_cpu_check
70
71.Lverify_cpu_noamd:
72 cmpl $0x756e6547,%ebx # GenuineIntel?
73 jnz .Lverify_cpu_check
74 cmpl $0x49656e69,%edx
75 jnz .Lverify_cpu_check
76 cmpl $0x6c65746e,%ecx
77 jnz .Lverify_cpu_check
78
79 # only call IA32_MISC_ENABLE when:
80 # family > 6 || (family == 6 && model >= 0xd)
81 movl $0x1, %eax # check CPU family and model
82 cpuid
83 movl %eax, %ecx
84
85 andl $0x0ff00f00, %eax # mask family and extended family
86 shrl $8, %eax
87 cmpl $6, %eax
88 ja .Lverify_cpu_clear_xd # family > 6, ok
89 jb .Lverify_cpu_check # family < 6, skip
90
91 andl $0x000f00f0, %ecx # mask model and extended model
92 shrl $4, %ecx
93 cmpl $0xd, %ecx
94 jb .Lverify_cpu_check # family == 6, model < 0xd, skip
95
96.Lverify_cpu_clear_xd:
97 movl $MSR_IA32_MISC_ENABLE, %ecx
98 rdmsr
99 btrl $2, %edx # clear MSR_IA32_MISC_ENABLE_XD_DISABLE
100 jnc .Lverify_cpu_check # only write MSR if bit was changed
101 wrmsr
102
103.Lverify_cpu_check:
104 movl $0x1,%eax # Does the cpu have what it takes
105 cpuid
106 andl $REQUIRED_MASK0,%edx
107 xorl $REQUIRED_MASK0,%edx
108 jnz .Lverify_cpu_no_longmode
109
110 movl $0x80000000,%eax # See if extended cpuid is implemented
111 cpuid
112 cmpl $0x80000001,%eax
113 jb .Lverify_cpu_no_longmode # no extended cpuid
114
115 movl $0x80000001,%eax # Does the cpu have what it takes
116 cpuid
117 andl $REQUIRED_MASK1,%edx
118 xorl $REQUIRED_MASK1,%edx
119 jnz .Lverify_cpu_no_longmode
120
121.Lverify_cpu_sse_test:
122 movl $1,%eax
123 cpuid
124 andl $SSE_MASK,%edx
125 cmpl $SSE_MASK,%edx
126 je .Lverify_cpu_sse_ok
127 test %di,%di
128 jz .Lverify_cpu_no_longmode # only try to force SSE on AMD
129 movl $MSR_K7_HWCR,%ecx
130 rdmsr
131 btr $15,%eax # enable SSE
132 wrmsr
133 xor %di,%di # don't loop
134 jmp .Lverify_cpu_sse_test # try again
135
136.Lverify_cpu_no_longmode:
137 popf # Restore caller passed flags
138 movl $1,%eax
139 RET
140.Lverify_cpu_sse_ok:
141 popf # Restore caller passed flags
142 xorl %eax, %eax
143 RET
144SYM_FUNC_END(verify_cpu)