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x86/mce: Handle broadcasted MCE gracefully with kexec

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When we are about to kexec a crash kernel and right then and there a
broadcasted MCE fires while we're still in the first kernel and while
the other CPUs remain in a holding pattern, the #MC handler of the
first kernel will timeout and then panic due to never completing MCE
synchronization.

Handle this in a similar way as to when the CPUs are offlined when that
broadcasted MCE happens.

[ Boris: rewrote commit message and comments. ]

Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Xunlei Pang <xlpang@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Tony Luck <tony.luck@intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: kexec@lists.infradead.org
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/1487857012-9059-1-git-send-email-xlpang@redhat.com
Link: http://lkml.kernel.org/r/20170313095019.19351-1-bp@alien8.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Xunlei Pang 2017-03-13 10:50:19 +01:00 committed by Thomas Gleixner
parent 4495c08e84
commit 5bc329503e
3 changed files with 20 additions and 4 deletions
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1
arch/x86/include/asm/reboot.h
View File

@ -15,6 +15,7 @@ struct machine_ops {
};
extern struct machine_ops machine_ops;
extern int crashing_cpu;
void native_machine_crash_shutdown(struct pt_regs *regs);
void native_machine_shutdown(void);

18
arch/x86/kernel/cpu/mcheck/mce.c
View File

@ -49,6 +49,7 @@
#include <asm/tlbflush.h>
#include <asm/mce.h>
#include <asm/msr.h>
#include <asm/reboot.h>
#include "mce-internal.h"
@ -1127,9 +1128,22 @@ void do_machine_check(struct pt_regs *regs, long error_code)
* on Intel.
*/
int lmce = 1;
int cpu = smp_processor_id();
/* If this CPU is offline, just bail out. */
if (cpu_is_offline(smp_processor_id())) {
/*
* Cases where we avoid rendezvous handler timeout:
* 1) If this CPU is offline.
*
* 2) If crashing_cpu was set, e.g. we're entering kdump and we need to
* skip those CPUs which remain looping in the 1st kernel - see
* crash_nmi_callback().
*
* Note: there still is a small window between kexec-ing and the new,
* kdump kernel establishing a new #MC handler where a broadcasted MCE
* might not get handled properly.
*/
if (cpu_is_offline(cpu) ||
(crashing_cpu != -1 && crashing_cpu != cpu)) {
u64 mcgstatus;
mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS);

5
arch/x86/kernel/reboot.c
View File

@ -765,10 +765,11 @@ void machine_crash_shutdown(struct pt_regs *regs)
#endif
/* This is the CPU performing the emergency shutdown work. */
int crashing_cpu = -1;
#if defined(CONFIG_SMP)
/* This keeps a track of which one is crashing cpu. */
static int crashing_cpu;
static nmi_shootdown_cb shootdown_callback;
static atomic_t waiting_for_crash_ipi;