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7b27718bdb
yesterday I tried to reactivate my old 486 box and wanted to install a current Linux with latest kernel on it. But it turned out that the latest kernel does not boot because the machine crashes early in the setup code. After some debugging it turned out that the problem is the query_ist() function. If this interrupt with that function is called the machine simply locks up. It looks like a BIOS bug. Looking for a workaround for this problem I wrote the attached patch. It checks for the CPUID instruction and if it is not implemented it does not call the speedstep BIOS function. As far as I know speedstep should be available since some Pentium earliest. Alan Cox observed that it's available since the Pentium II, so cpuid levels 4 and 5 can be excluded altogether. H. Peter Anvin cleaned up the code some more: > Right in concept, but I dislike the implementation (duplication of the > CPU detect code we already have). Could you try this patch and see if > it works for you? which, with a small modification to fix a build error with it the resulting kernel boots on my machine. Signed-off-by: Joerg Roedel <joro@8bytes.org> Signed-off-by: "H. Peter Anvin" <hpa@zytor.com> Cc: <stable@kernel.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
255 lines
5.8 KiB
C
255 lines
5.8 KiB
C
/* -*- linux-c -*- ------------------------------------------------------- *
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright 2007 rPath, Inc. - All Rights Reserved
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*
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* This file is part of the Linux kernel, and is made available under
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* the terms of the GNU General Public License version 2.
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*
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* ----------------------------------------------------------------------- */
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/*
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* Check for obligatory CPU features and abort if the features are not
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* present. This code should be compilable as 16-, 32- or 64-bit
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* code, so be very careful with types and inline assembly.
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*
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* This code should not contain any messages; that requires an
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* additional wrapper.
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*
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* As written, this code is not safe for inclusion into the kernel
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* proper (after FPU initialization, in particular).
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*/
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#ifdef _SETUP
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# include "boot.h"
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# include "bitops.h"
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#endif
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#include <linux/types.h>
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#include <asm/cpufeature.h>
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#include <asm/processor-flags.h>
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#include <asm/required-features.h>
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#include <asm/msr-index.h>
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struct cpu_features cpu;
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static u32 cpu_vendor[3];
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static u32 err_flags[NCAPINTS];
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static const int req_level = CONFIG_X86_MINIMUM_CPU_FAMILY;
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static const u32 req_flags[NCAPINTS] =
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{
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REQUIRED_MASK0,
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REQUIRED_MASK1,
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REQUIRED_MASK2,
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REQUIRED_MASK3,
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REQUIRED_MASK4,
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REQUIRED_MASK5,
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REQUIRED_MASK6,
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REQUIRED_MASK7,
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};
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#define A32(a, b, c, d) (((d) << 24)+((c) << 16)+((b) << 8)+(a))
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static int is_amd(void)
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{
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return cpu_vendor[0] == A32('A', 'u', 't', 'h') &&
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cpu_vendor[1] == A32('e', 'n', 't', 'i') &&
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cpu_vendor[2] == A32('c', 'A', 'M', 'D');
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}
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static int is_centaur(void)
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{
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return cpu_vendor[0] == A32('C', 'e', 'n', 't') &&
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cpu_vendor[1] == A32('a', 'u', 'r', 'H') &&
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cpu_vendor[2] == A32('a', 'u', 'l', 's');
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}
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static int is_transmeta(void)
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{
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return cpu_vendor[0] == A32('G', 'e', 'n', 'u') &&
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cpu_vendor[1] == A32('i', 'n', 'e', 'T') &&
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cpu_vendor[2] == A32('M', 'x', '8', '6');
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}
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static int has_fpu(void)
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{
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u16 fcw = -1, fsw = -1;
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u32 cr0;
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asm("movl %%cr0,%0" : "=r" (cr0));
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if (cr0 & (X86_CR0_EM|X86_CR0_TS)) {
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cr0 &= ~(X86_CR0_EM|X86_CR0_TS);
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asm volatile("movl %0,%%cr0" : : "r" (cr0));
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}
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asm volatile("fninit ; fnstsw %0 ; fnstcw %1"
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: "+m" (fsw), "+m" (fcw));
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return fsw == 0 && (fcw & 0x103f) == 0x003f;
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}
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static int has_eflag(u32 mask)
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{
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u32 f0, f1;
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asm("pushfl ; "
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"pushfl ; "
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"popl %0 ; "
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"movl %0,%1 ; "
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"xorl %2,%1 ; "
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"pushl %1 ; "
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"popfl ; "
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"pushfl ; "
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"popl %1 ; "
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"popfl"
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: "=&r" (f0), "=&r" (f1)
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: "ri" (mask));
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return !!((f0^f1) & mask);
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}
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static void get_flags(void)
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{
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u32 max_intel_level, max_amd_level;
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u32 tfms;
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if (has_fpu())
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set_bit(X86_FEATURE_FPU, cpu.flags);
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if (has_eflag(X86_EFLAGS_ID)) {
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asm("cpuid"
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: "=a" (max_intel_level),
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"=b" (cpu_vendor[0]),
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"=d" (cpu_vendor[1]),
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"=c" (cpu_vendor[2])
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: "a" (0));
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if (max_intel_level >= 0x00000001 &&
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max_intel_level <= 0x0000ffff) {
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asm("cpuid"
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: "=a" (tfms),
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"=c" (cpu.flags[4]),
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"=d" (cpu.flags[0])
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: "a" (0x00000001)
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: "ebx");
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cpu.level = (tfms >> 8) & 15;
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cpu.model = (tfms >> 4) & 15;
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if (cpu.level >= 6)
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cpu.model += ((tfms >> 16) & 0xf) << 4;
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}
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asm("cpuid"
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: "=a" (max_amd_level)
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: "a" (0x80000000)
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: "ebx", "ecx", "edx");
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if (max_amd_level >= 0x80000001 &&
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max_amd_level <= 0x8000ffff) {
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u32 eax = 0x80000001;
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asm("cpuid"
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: "+a" (eax),
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"=c" (cpu.flags[6]),
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"=d" (cpu.flags[1])
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: : "ebx");
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}
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}
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}
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/* Returns a bitmask of which words we have error bits in */
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static int check_flags(void)
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{
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u32 err;
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int i;
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err = 0;
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for (i = 0; i < NCAPINTS; i++) {
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err_flags[i] = req_flags[i] & ~cpu.flags[i];
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if (err_flags[i])
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err |= 1 << i;
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}
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return err;
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}
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/*
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* Returns -1 on error.
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*
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* *cpu_level is set to the current CPU level; *req_level to the required
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* level. x86-64 is considered level 64 for this purpose.
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*
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* *err_flags_ptr is set to the flags error array if there are flags missing.
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*/
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int check_cpu(int *cpu_level_ptr, int *req_level_ptr, u32 **err_flags_ptr)
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{
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int err;
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memset(&cpu.flags, 0, sizeof cpu.flags);
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cpu.level = 3;
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if (has_eflag(X86_EFLAGS_AC))
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cpu.level = 4;
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get_flags();
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err = check_flags();
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if (test_bit(X86_FEATURE_LM, cpu.flags))
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cpu.level = 64;
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if (err == 0x01 &&
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!(err_flags[0] &
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~((1 << X86_FEATURE_XMM)|(1 << X86_FEATURE_XMM2))) &&
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is_amd()) {
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/* If this is an AMD and we're only missing SSE+SSE2, try to
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turn them on */
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u32 ecx = MSR_K7_HWCR;
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u32 eax, edx;
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asm("rdmsr" : "=a" (eax), "=d" (edx) : "c" (ecx));
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eax &= ~(1 << 15);
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asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));
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get_flags(); /* Make sure it really did something */
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err = check_flags();
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} else if (err == 0x01 &&
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!(err_flags[0] & ~(1 << X86_FEATURE_CX8)) &&
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is_centaur() && cpu.model >= 6) {
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/* If this is a VIA C3, we might have to enable CX8
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explicitly */
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u32 ecx = MSR_VIA_FCR;
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u32 eax, edx;
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asm("rdmsr" : "=a" (eax), "=d" (edx) : "c" (ecx));
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eax |= (1<<1)|(1<<7);
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asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));
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set_bit(X86_FEATURE_CX8, cpu.flags);
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err = check_flags();
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} else if (err == 0x01 && is_transmeta()) {
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/* Transmeta might have masked feature bits in word 0 */
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u32 ecx = 0x80860004;
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u32 eax, edx;
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u32 level = 1;
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asm("rdmsr" : "=a" (eax), "=d" (edx) : "c" (ecx));
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asm("wrmsr" : : "a" (~0), "d" (edx), "c" (ecx));
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asm("cpuid"
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: "+a" (level), "=d" (cpu.flags[0])
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: : "ecx", "ebx");
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asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));
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err = check_flags();
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}
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if (err_flags_ptr)
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*err_flags_ptr = err ? err_flags : NULL;
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if (cpu_level_ptr)
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*cpu_level_ptr = cpu.level;
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if (req_level_ptr)
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*req_level_ptr = req_level;
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return (cpu.level < req_level || err) ? -1 : 0;
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}
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