linux/arch/x86/kernel/crash.c
Cliff Wickman 5edd19af18 x86, UV: Make kdump avoid stack dumps
UV NMI callback's should not write stack dumps when a kdump is to be written.

When invoking the crash kernel to write a dump, kdump_nmi_shootdown_cpus()
uses NMI's to get all the cpu's to save their register context and halt.

But the NMI interrupt handler runs a callback list.  This patch sets a flag
to prevent any of those callbacks from interfering with the halt of the cpu.

For UV, which currently has the only callback to which this is relevant, the
uv_handle_nmi() callback should not do dumping of stacks.

The 'in_crash_kexec' flag is defined as an extern in kdebug.h firstly
because x2apic_uv_x.c includes it.  Secondly because some future callback
might need the flag to know that it should not enter the debugger.
(Such a scenario was in fact present in the 2.6.32 kernel, SuSE distribution,
 where a call to kdb needed to be avoided.)

Signed-off-by: Cliff Wickman <cpw@sgi.com>
LKML-Reference: <E1ObLvt-0005UZ-Va@eag09.americas.sgi.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2010-07-21 11:33:27 -07:00

110 lines
2.4 KiB
C

/*
* Architecture specific (i386/x86_64) functions for kexec based crash dumps.
*
* Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
*
* Copyright (C) IBM Corporation, 2004. All rights reserved.
*
*/
#include <linux/init.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/smp.h>
#include <linux/reboot.h>
#include <linux/kexec.h>
#include <linux/delay.h>
#include <linux/elf.h>
#include <linux/elfcore.h>
#include <asm/processor.h>
#include <asm/hardirq.h>
#include <asm/nmi.h>
#include <asm/hw_irq.h>
#include <asm/apic.h>
#include <asm/hpet.h>
#include <linux/kdebug.h>
#include <asm/cpu.h>
#include <asm/reboot.h>
#include <asm/virtext.h>
int in_crash_kexec;
#if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)
static void kdump_nmi_callback(int cpu, struct die_args *args)
{
struct pt_regs *regs;
#ifdef CONFIG_X86_32
struct pt_regs fixed_regs;
#endif
regs = args->regs;
#ifdef CONFIG_X86_32
if (!user_mode_vm(regs)) {
crash_fixup_ss_esp(&fixed_regs, regs);
regs = &fixed_regs;
}
#endif
crash_save_cpu(regs, cpu);
/* Disable VMX or SVM if needed.
*
* We need to disable virtualization on all CPUs.
* Having VMX or SVM enabled on any CPU may break rebooting
* after the kdump kernel has finished its task.
*/
cpu_emergency_vmxoff();
cpu_emergency_svm_disable();
disable_local_APIC();
}
static void kdump_nmi_shootdown_cpus(void)
{
in_crash_kexec = 1;
nmi_shootdown_cpus(kdump_nmi_callback);
disable_local_APIC();
}
#else
static void kdump_nmi_shootdown_cpus(void)
{
/* There are no cpus to shootdown */
}
#endif
void native_machine_crash_shutdown(struct pt_regs *regs)
{
/* This function is only called after the system
* has panicked or is otherwise in a critical state.
* The minimum amount of code to allow a kexec'd kernel
* to run successfully needs to happen here.
*
* In practice this means shooting down the other cpus in
* an SMP system.
*/
/* The kernel is broken so disable interrupts */
local_irq_disable();
kdump_nmi_shootdown_cpus();
/* Booting kdump kernel with VMX or SVM enabled won't work,
* because (among other limitations) we can't disable paging
* with the virt flags.
*/
cpu_emergency_vmxoff();
cpu_emergency_svm_disable();
lapic_shutdown();
#if defined(CONFIG_X86_IO_APIC)
disable_IO_APIC();
#endif
#ifdef CONFIG_HPET_TIMER
hpet_disable();
#endif
crash_save_cpu(regs, safe_smp_processor_id());
}