1 /* -*- linux-c -*- ------------------------------------------------------- *
3 * Copyright (C) 1991, 1992 Linus Torvalds
4 * Copyright 2007 rPath, Inc. - All Rights Reserved
6 * This file is part of the Linux kernel, and is made available under
7 * the terms of the GNU General Public License version 2.
9 * ----------------------------------------------------------------------- */
12 * Check for obligatory CPU features and abort if the features are not
13 * present. This code should be compilable as 16-, 32- or 64-bit
14 * code, so be very careful with types and inline assembly.
16 * This code should not contain any messages; that requires an
19 * As written, this code is not safe for inclusion into the kernel
20 * proper (after FPU initialization, in particular).
26 #include <linux/types.h>
27 #include <asm/processor-flags.h>
28 #include <asm/required-features.h>
29 #include <asm/msr-index.h>
31 static u32 err_flags[NCAPINTS];
33 static const int req_level = CONFIG_X86_MINIMUM_CPU_FAMILY;
35 static const u32 req_flags[NCAPINTS] =
39 0, /* REQUIRED_MASK2 not implemented in this file */
40 0, /* REQUIRED_MASK3 not implemented in this file */
42 0, /* REQUIRED_MASK5 not implemented in this file */
44 0, /* REQUIRED_MASK7 not implemented in this file */
47 #define A32(a, b, c, d) (((d) << 24)+((c) << 16)+((b) << 8)+(a))
49 static int is_amd(void)
51 return cpu_vendor[0] == A32('A', 'u', 't', 'h') &&
52 cpu_vendor[1] == A32('e', 'n', 't', 'i') &&
53 cpu_vendor[2] == A32('c', 'A', 'M', 'D');
56 static int is_centaur(void)
58 return cpu_vendor[0] == A32('C', 'e', 'n', 't') &&
59 cpu_vendor[1] == A32('a', 'u', 'r', 'H') &&
60 cpu_vendor[2] == A32('a', 'u', 'l', 's');
63 static int is_transmeta(void)
65 return cpu_vendor[0] == A32('G', 'e', 'n', 'u') &&
66 cpu_vendor[1] == A32('i', 'n', 'e', 'T') &&
67 cpu_vendor[2] == A32('M', 'x', '8', '6');
70 static int is_intel(void)
72 return cpu_vendor[0] == A32('G', 'e', 'n', 'u') &&
73 cpu_vendor[1] == A32('i', 'n', 'e', 'I') &&
74 cpu_vendor[2] == A32('n', 't', 'e', 'l');
77 /* Returns a bitmask of which words we have error bits in */
78 static int check_cpuflags(void)
84 for (i = 0; i < NCAPINTS; i++) {
85 err_flags[i] = req_flags[i] & ~cpu.flags[i];
94 * Returns -1 on error.
96 * *cpu_level is set to the current CPU level; *req_level to the required
97 * level. x86-64 is considered level 64 for this purpose.
99 * *err_flags_ptr is set to the flags error array if there are flags missing.
101 int check_cpu(int *cpu_level_ptr, int *req_level_ptr, u32 **err_flags_ptr)
105 memset(&cpu.flags, 0, sizeof cpu.flags);
108 if (has_eflag(X86_EFLAGS_AC))
112 err = check_cpuflags();
114 if (test_bit(X86_FEATURE_LM, cpu.flags))
119 ~((1 << X86_FEATURE_XMM)|(1 << X86_FEATURE_XMM2))) &&
121 /* If this is an AMD and we're only missing SSE+SSE2, try to
124 u32 ecx = MSR_K7_HWCR;
127 asm("rdmsr" : "=a" (eax), "=d" (edx) : "c" (ecx));
129 asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));
131 get_cpuflags(); /* Make sure it really did something */
132 err = check_cpuflags();
133 } else if (err == 0x01 &&
134 !(err_flags[0] & ~(1 << X86_FEATURE_CX8)) &&
135 is_centaur() && cpu.model >= 6) {
136 /* If this is a VIA C3, we might have to enable CX8
139 u32 ecx = MSR_VIA_FCR;
142 asm("rdmsr" : "=a" (eax), "=d" (edx) : "c" (ecx));
143 eax |= (1<<1)|(1<<7);
144 asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));
146 set_bit(X86_FEATURE_CX8, cpu.flags);
147 err = check_cpuflags();
148 } else if (err == 0x01 && is_transmeta()) {
149 /* Transmeta might have masked feature bits in word 0 */
151 u32 ecx = 0x80860004;
155 asm("rdmsr" : "=a" (eax), "=d" (edx) : "c" (ecx));
156 asm("wrmsr" : : "a" (~0), "d" (edx), "c" (ecx));
158 : "+a" (level), "=d" (cpu.flags[0])
160 asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));
162 err = check_cpuflags();
163 } else if (err == 0x01 &&
164 !(err_flags[0] & ~(1 << X86_FEATURE_PAE)) &&
165 is_intel() && cpu.level == 6 &&
166 (cpu.model == 9 || cpu.model == 13)) {
167 /* PAE is disabled on this Pentium M but can be forced */
168 if (cmdline_find_option_bool("forcepae")) {
169 puts("WARNING: Forcing PAE in CPU flags\n");
170 set_bit(X86_FEATURE_PAE, cpu.flags);
171 err = check_cpuflags();
174 puts("WARNING: PAE disabled. Use parameter 'forcepae' to enable at your own risk!\n");
179 *err_flags_ptr = err ? err_flags : NULL;
181 *cpu_level_ptr = cpu.level;
183 *req_level_ptr = req_level;
185 return (cpu.level < req_level || err) ? -1 : 0;