x86, MCE: Drain mcelog buffer

Add a function which drains whatever MCEs were logged in already during
boot and before the decoder chains were registered.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index c3c66ac6ef74..5be2464cce6a 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -189,9 +189,48 @@ void mce_log(struct mce *mce)
         set_bit(0, &mce_need_notify);
 }
 
+static void drain_mcelog_buffer(void)
+{
+        unsigned int next, i, prev = 0;
+
+        next = rcu_dereference_check_mce(mcelog.next);
+
+        do {
+                struct mce *m;
+
+                /* drain what was logged during boot */
+                for (i = prev; i < next; i++) {
+                        unsigned long start = jiffies;
+                        unsigned retries = 1;
+
+                        m = &mcelog.entry[i];
+
+                        while (!m->finished) {
+                                if (time_after_eq(jiffies, start + 2*retries))
+                                        retries++;
+
+                                cpu_relax();
+
+                                if (!m->finished && retries >= 4) {
+                                        pr_err("MCE: skipping error being logged currently!\n");
+                                        break;
+                                }
+                        }
+                        smp_rmb();
+                        atomic_notifier_call_chain(&x86_mce_decoder_chain, 0, m);
+                }
+
+                memset(mcelog.entry + prev, 0, (next - prev) * sizeof(*m));
+                prev = next;
+                next = cmpxchg(&mcelog.next, prev, 0);
+        } while (next != prev);
+}
+
+
 void mce_register_decode_chain(struct notifier_block *nb)
 {
         atomic_notifier_chain_register(&x86_mce_decoder_chain, nb);
+        drain_mcelog_buffer();
 }
 EXPORT_SYMBOL_GPL(mce_register_decode_chain);