xref: /openbmc/linux/arch/x86/kernel/verify_cpu.S (revision 14b476e0)
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/msr-index.h>
33
34SYM_FUNC_START_LOCAL(verify_cpu)
35	pushf				# Save caller passed flags
36	push	$0			# Kill any dangerous flags
37	popf
38
39#ifndef __x86_64__
40	pushfl				# standard way to check for cpuid
41	popl	%eax
42	movl	%eax,%ebx
43	xorl	$0x200000,%eax
44	pushl	%eax
45	popfl
46	pushfl
47	popl	%eax
48	cmpl	%eax,%ebx
49	jz	.Lverify_cpu_no_longmode	# cpu has no cpuid
50#endif
51
52	movl	$0x0,%eax		# See if cpuid 1 is implemented
53	cpuid
54	cmpl	$0x1,%eax
55	jb	.Lverify_cpu_no_longmode	# no cpuid 1
56
57	xor	%di,%di
58	cmpl	$0x68747541,%ebx	# AuthenticAMD
59	jnz	.Lverify_cpu_noamd
60	cmpl	$0x69746e65,%edx
61	jnz	.Lverify_cpu_noamd
62	cmpl	$0x444d4163,%ecx
63	jnz	.Lverify_cpu_noamd
64	mov	$1,%di			# cpu is from AMD
65	jmp	.Lverify_cpu_check
66
67.Lverify_cpu_noamd:
68	cmpl	$0x756e6547,%ebx        # GenuineIntel?
69	jnz	.Lverify_cpu_check
70	cmpl	$0x49656e69,%edx
71	jnz	.Lverify_cpu_check
72	cmpl	$0x6c65746e,%ecx
73	jnz	.Lverify_cpu_check
74
75	# only call IA32_MISC_ENABLE when:
76	# family > 6 || (family == 6 && model >= 0xd)
77	movl	$0x1, %eax		# check CPU family and model
78	cpuid
79	movl	%eax, %ecx
80
81	andl	$0x0ff00f00, %eax	# mask family and extended family
82	shrl	$8, %eax
83	cmpl	$6, %eax
84	ja	.Lverify_cpu_clear_xd	# family > 6, ok
85	jb	.Lverify_cpu_check	# family < 6, skip
86
87	andl	$0x000f00f0, %ecx	# mask model and extended model
88	shrl	$4, %ecx
89	cmpl	$0xd, %ecx
90	jb	.Lverify_cpu_check	# family == 6, model < 0xd, skip
91
92.Lverify_cpu_clear_xd:
93	movl	$MSR_IA32_MISC_ENABLE, %ecx
94	rdmsr
95	btrl	$2, %edx		# clear MSR_IA32_MISC_ENABLE_XD_DISABLE
96	jnc	.Lverify_cpu_check	# only write MSR if bit was changed
97	wrmsr
98
99.Lverify_cpu_check:
100	movl    $0x1,%eax		# Does the cpu have what it takes
101	cpuid
102	andl	$REQUIRED_MASK0,%edx
103	xorl	$REQUIRED_MASK0,%edx
104	jnz	.Lverify_cpu_no_longmode
105
106	movl    $0x80000000,%eax	# See if extended cpuid is implemented
107	cpuid
108	cmpl    $0x80000001,%eax
109	jb      .Lverify_cpu_no_longmode	# no extended cpuid
110
111	movl    $0x80000001,%eax	# Does the cpu have what it takes
112	cpuid
113	andl    $REQUIRED_MASK1,%edx
114	xorl    $REQUIRED_MASK1,%edx
115	jnz     .Lverify_cpu_no_longmode
116
117.Lverify_cpu_sse_test:
118	movl	$1,%eax
119	cpuid
120	andl	$SSE_MASK,%edx
121	cmpl	$SSE_MASK,%edx
122	je	.Lverify_cpu_sse_ok
123	test	%di,%di
124	jz	.Lverify_cpu_no_longmode	# only try to force SSE on AMD
125	movl	$MSR_K7_HWCR,%ecx
126	rdmsr
127	btr	$15,%eax		# enable SSE
128	wrmsr
129	xor	%di,%di			# don't loop
130	jmp	.Lverify_cpu_sse_test	# try again
131
132.Lverify_cpu_no_longmode:
133	popf				# Restore caller passed flags
134	movl $1,%eax
135	RET
136.Lverify_cpu_sse_ok:
137	popf				# Restore caller passed flags
138	xorl %eax, %eax
139	RET
140SYM_FUNC_END(verify_cpu)
141