mces_seen is a Per-CPU variable which should only be accessed by Per-CPU as possible. So the
clear operation of mces_seen should also be local to Per-CPU rather than monarch CPU.
Meanwhile, there is also a potential risk that mces_seen will not be be cleared if a timeout
occurs in mce_end for monarch CPU. As a result, the stale value of mces_seen will reappear
on the next mce.
Based on the above reasons, this patch distribute the clear operation of mces_seen to Per-CPU
rather than only monarch CPU.
* From v1
* Add Reviewed-by: Andi Kleen
* Put the clear operation of mces_seen before the MCG_STATUS write.
* From v2
* Fix some misspelling in the patch message.
Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Chen Yucong <slaoub@xxxxxxxxx>
---
arch/x86/kernel/cpu/mcheck/mce.c | 18 +++++++-----------
1 file changed, 7 insertions(+), 11 deletions(-)
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 68317c8..966a5f5 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -785,13 +785,6 @@ static void mce_reign(void)
*/
if (global_worst <= MCE_KEEP_SEVERITY && mca_cfg.tolerant < 3)
mce_panic("Machine check from unknown source", NULL, NULL);
-
- /*
- * Now clear all the mces_seen so that they don't reappear on
- * the next mce.
- */
- for_each_possible_cpu(cpu)
- memset(&per_cpu(mces_seen, cpu), 0, sizeof(struct mce));
}
static atomic_t global_nwo;
@@ -1137,9 +1130,6 @@ void do_machine_check(struct pt_regs *regs, long error_code)
}
}
- /* mce_clear_state will clear *final, save locally for use later */
- m = *final;
-
if (!no_way_out)
mce_clear_state(toclear);
@@ -1161,7 +1151,7 @@ void do_machine_check(struct pt_regs *regs, long error_code)
mce_panic("Fatal machine check on current CPU", &m, msg);
if (worst == MCE_AR_SEVERITY) {
/* schedule action before return to userland */
- mce_save_info(m.addr, m.mcgstatus & MCG_STATUS_RIPV);
+ mce_save_info(final->addr, final->mcgstatus & MCG_STATUS_RIPV);
set_thread_flag(TIF_MCE_NOTIFY);
} else if (kill_it) {
force_sig(SIGBUS, current);
@@ -1170,6 +1160,12 @@ void do_machine_check(struct pt_regs *regs, long error_code)
if (worst > 0)
mce_report_event(regs);
+
+ /*
+ * Now clear the mces_seen of current CPU -*final - so that it does not
+ * reappear on the next mce.
+ */
+ memset(final, 0, sizeof(struct mce));
mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);
out:
atomic_dec(&mce_entry);
--
1.7.10.4
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