/*
* arch/i386/cpu/bugs.c
*
* Copyright (C) 1994 Linus Torvalds
*
* Cyrix stuff, June 1998 by:
* - Rafael R. Reilova (moved everything from head.S),
* <rreilova@ececs.uc.edu>
* - Channing Corn (tests & fixes),
* - Andrew D. Balsa (code cleanup).
*/
#include <linux/init.h>
#include <linux/utsname.h>
#include <asm/processor.h>
#include <asm/i387.h>
#include <asm/msr.h>
#include <asm/paravirt.h>
#include <asm/alternative.h>
static int __init no_halt(char *s)
{
boot_cpu_data.hlt_works_ok = 0;
return 1;
}
__setup("no-hlt", no_halt);
static int __init mca_pentium(char *s)
{
mca_pentium_flag = 1;
return 1;
}
__setup("mca-pentium", mca_pentium);
static int __init no_387(char *s)
{
boot_cpu_data.hard_math = 0;
write_cr0(0xE | read_cr0());
return 1;
}
__setup("no387", no_387);
static double __initdata x = 4195835.0;
static double __initdata y = 3145727.0;
/*
* This used to check for exceptions..
* However, it turns out that to support that,
* the XMM trap handlers basically had to
* be buggy. So let's have a correct XMM trap
* handler, and forget about printing out
* some status at boot.
*
* We should really only care about bugs here
* anyway. Not features.
*/
static void __init check_fpu(void)
{
if (!boot_cpu_data.hard_math) {
#ifndef CONFIG_MATH_EMULATION
printk(KERN_EMERG "No coprocessor found and no math emulation present.\n");
printk(KERN_EMERG "Giving up.\n");
for (;;) ;
#endif
return;
}
/* trap_init() enabled FXSR and company _before_ testing for FP problems here. */
/* Test for the divl bug.. */
__asm__("fninit\n\t"
"fldl %1\n\t"
"fdivl %2\n\t"
"fmull %2\n\t"
"fldl %1\n\t"
"fsubp %%st,%%st(1)\n\t"
"fistpl %0\n\t"
"fwait\n\t"
"fninit"
: "=m" (*&boot_cpu_data.fdiv_bug)
: "m" (*&x), "m" (*&y));
if (boot_cpu_data.fdiv_bug)
printk("Hmm, FPU with FDIV bug.\n");
}
static void __init check_hlt(void)
{
if (paravirt_enabled())
return;
printk(KERN_INFO "Checking 'hlt' instruction... ");
if (!boot_cpu_data.hlt_works_ok) {
printk("disabled\n");
return;
}
halt();
halt();
halt();
halt();
printk("OK.\n");
}
/*
* Most 386 processors have a bug where a POPAD can lock the
* machine even from user space.
*/
static void __init check_popad(void)
{
#ifndef CONFIG_X86_POPAD_OK
int res, inp = (int) &res;
printk(KERN_INFO "Checking for popad bug... ");
__asm__ __volatile__(
"movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx "
: "=&a" (res)
: "d" (inp)
: "ecx", "edi" );
/* If this fails, it means that any user program may lock the CPU hard. Too bad. */
if (res != 12345678) printk( "Buggy.\n" );
else printk( "OK.\n" );
#endif
}
/*
* Check whether we are able to run this kernel safely on SMP.
*
* - In order to run on a i386, we need to be compiled for i386
* (for due to lack of "invlpg" and working WP on a i386)
* - In order to run on anything without a TSC, we need to be
* compiled for a i486.
* - In order to support the local APIC on a buggy Pentium machine,
* we need to be compiled with CONFIG_X86_GOOD_APIC disabled,
* which happens implicitly if compiled for a Pentium or lower
* (unless an advanced selection of CPU features is used) as an
* otherwise config implies a properly working local APIC without
* the need to do extra reads from the APIC.
*/
static void __init check_config(void)
{
/*
* We'd better not be a i386 if we're configured to use some
* i486+ only features! (WP works in supervisor mode and the
* new "invlpg" and "bswap" instructions)
*/
#if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || defined(CONFIG_X86_BSWAP)
if (boot_cpu_data.x86 == 3)
panic("Kernel requires i486+ for 'invlpg' and other features");
#endif
/*
* If we configured ourselves for a TSC, we'd better have one!
*/
#ifdef CONFIG_X86_TSC
if (!cpu_has_tsc && !tsc_disable)
panic("Kernel compiled for Pentium+, requires TSC feature!");
#endif
/*
* If we were told we had a good local APIC, check for buggy Pentia,
* i.e. all B steppings and the C2 stepping of P54C when using their
* integrated APIC (see 11AP erratum in "Pentium Processor
* Specification Update").
*/
#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86_GOOD_APIC)
if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL
&& cpu_has_apic
&& boot_cpu_data.x86 == 5
&& boot_cpu_data.x86_model == 2
&& (boot_cpu_data.x86_mask < 6 || boot_cpu_data.x86_mask == 11))
panic("Kernel compiled for PMMX+, assumes a local APIC without the read-before-write bug!");
#endif
}
void __init check_bugs(void)
{
identify_boot_cpu();
#ifndef CONFIG_SMP
printk("CPU: ");
print_cpu_info(&boot_cpu_data);
#endif
check_config();
check_fpu();
check_hlt();
check_popad();
init_utsname()->machine[1] = '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
alternative_instructions();
}
