This is a note to let you know that I've just added the patch titled
x86/mce: Handle broadcasted MCE gracefully with kexec
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-mce-handle-broadcasted-mce-gracefully-with-kexec.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Sun Mar 18 16:55:33 CET 2018
From: Xunlei Pang <xlpang@xxxxxxxxxx>
Date: Mon, 13 Mar 2017 10:50:19 +0100
Subject: x86/mce: Handle broadcasted MCE gracefully with kexec
From: Xunlei Pang <xlpang@xxxxxxxxxx>
[ Upstream commit 5bc329503e8191c91c4c40836f062ef771d8ba83 ]
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@xxxxxxxxx>
Signed-off-by: Xunlei Pang <xlpang@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Acked-by: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: kexec@xxxxxxxxxxxxxxxxxxx
Cc: linux-edac <linux-edac@xxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1487857012-9059-1-git-send-email-xlpang@xxxxxxxxxx
Link: http://lkml.kernel.org/r/20170313095019.19351-1-bp@xxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/reboot.h | 1 +
arch/x86/kernel/cpu/mcheck/mce.c | 18 ++++++++++++++++--
arch/x86/kernel/reboot.c | 5 +++--
3 files changed, 20 insertions(+), 4 deletions(-)
--- a/arch/x86/include/asm/reboot.h
+++ b/arch/x86/include/asm/reboot.h
@@ -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);
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -48,6 +48,7 @@
#include <asm/tlbflush.h>
#include <asm/mce.h>
#include <asm/msr.h>
+#include <asm/reboot.h>
#include "mce-internal.h"
@@ -1081,9 +1082,22 @@ void do_machine_check(struct pt_regs *re
* 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);
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -769,10 +769,11 @@ void machine_crash_shutdown(struct pt_re
#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;
Patches currently in stable-queue which might be from xlpang@xxxxxxxxxx are
queue-4.9/rtmutex-fix-pi-chain-order-integrity.patch
queue-4.9/x86-mce-handle-broadcasted-mce-gracefully-with-kexec.patch