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SubjectRe: Oops in 2.4.0-ac5
Date
On Wed, 10 Jan 2001 15:23:14 -0500, 
Nathan Walp <faceprint@faceprint.com> wrote:
>Here it is... I opted to cut out the 1200-odd warnings, which from the
>look of them were all because i'm running it under 2.4.0-ac4 (which
>boots fine).

ksymoops defaults to using /proc entries from the current system. This
is fine for most people but you have to override the default when
decoding an oops from another kernel.

ksymoops -KL -m /boot/System.map-2.4.0-ac5

ignores the running ksyms and lsmod files, removing your warnings.

>>>EIP; c01129ba <setup_apic_nmi_watchdog+a/90> <=====
>Trace; c0100191 <L6+0/2>
>Code; c01129ba <setup_apic_nmi_watchdog+a/90>
>00000000 <_EIP>:
>Code; c01129ba <setup_apic_nmi_watchdog+a/90> <=====
> 0: 0f 30 wrmsr <=====
>Code; c01129bc <setup_apic_nmi_watchdog+c/90>

This is why my original NMI for UP code in kdb uses wrmsr_eio() instead
of wrmsr. wrmsr_eio() catches errors where the APIC does not support
the msr and returns EIO instead of oopsing and taking the kernel with
it. I could never persuade Ingo to use wrmsr_eio() and check the
return code, maybe this will change his mind. Extract from kdb v1.7.

/*
* {rd,wr}msr_eio by HPA, moved from arch/i386/msr.c to here.
* Keith Owens.
*/

/* Note: "err" is handled in a funny way below. Otherwise one version
of gcc or another breaks. */

extern inline int wrmsr_eio(u32 reg, u32 eax, u32 edx)
{
int err;

asm volatile(
"1: wrmsr\n"
"2:\n"
".section .fixup,\"ax\"\n"
"3: movl %4,%0\n"
" jmp 2b\n"
".previous\n"
".section __ex_table,\"a\"\n"
" .align 4\n"
" .long 1b,3b\n"
".previous"
: "=&bDS" (err)
: "a" (eax), "d" (edx), "c" (reg), "i" (-EIO), "0" (0));

return err;
}

.....

/*
* Activate or deactivate NMI watchdog via a local APIC.
*/

int setup_apic_nmi_watchdog(int value)
{
int ret, eax;

if (!test_bit(X86_FEATURE_APIC, &boot_cpu_data.x86_capability))
return(-EIO);
if (nmi_watchdog_source && nmi_watchdog_source != 1)
return(0); /* Not using local APIC */
/* Disable performance counters 0, 1 for all NMI changes */
nmi_watchdog = proc_nmi_watchdog = nmi_watchdog_source = 0;
if ((ret = wrmsr_eio(EVNTSEL0, 0, 0)) ||
(ret = wrmsr_eio(EVNTSEL1, 0, 0)) ||
(ret = wrmsr_eio(PERFCTR0, 0, 0)) ||
(ret = wrmsr_eio(PERFCTR1, 0, 0)))
goto exit;
if (!value)
return(0);
/* Must set before activation to catch first NMI */
nmi_watchdog = proc_nmi_watchdog = nmi_watchdog_source = 1;
eax = 1 << 20 /* Interrupt on overflow */
| 1 << 17 /* OS mode */
| 1 << 16 /* User mode */
| 0x79; /* Event, cpu clocks not halted */
if ((ret = wrmsr_eio(EVNTSEL1, eax, 0))
|| (ret = set_nmi_counter_local()))
goto exit;
apic_write_around(APIC_LVTPC, APIC_DM_NMI);
eax = 1 << 22; /* Enable performance counters, only using ctr1 */
ret = wrmsr_eio(EVNTSEL0, eax, 0);
exit:
if (ret)
nmi_watchdog = proc_nmi_watchdog = nmi_watchdog_source = 0;
else
printk(KERN_INFO "Activated NMI via local APIC\n");
return(ret);
}



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