powerpc/mce: hookup memory_failure for UE errors

If we are in user space and hit a UE error, we now have the
basic infrastructure to walk the page tables and find out
the effective address that was accessed, since the DAR
is not valid.

We use a work_queue content to hookup the bad pfn, any
other context causes problems, since memory_failure itself
can call into schedule() via lru_drain_ bits.

We could probably poison the struct page to avoid a race
between detection and taking corrective action.

Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index 1af7c55..742e465 100644 (file)
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -39,11 +39,21 @@ static DEFINE_PER_CPU(struct machine_check_event[MAX_MC_EVT], mce_event);
 static DEFINE_PER_CPU(int, mce_queue_count);
 static DEFINE_PER_CPU(struct machine_check_event[MAX_MC_EVT], mce_event_queue);
 
+/* Queue for delayed MCE UE events. */
+static DEFINE_PER_CPU(int, mce_ue_count);
+static DEFINE_PER_CPU(struct machine_check_event[MAX_MC_EVT],
+                                       mce_ue_event_queue);
+
 static void machine_check_process_queued_event(struct irq_work *work);
+void machine_check_ue_event(struct machine_check_event *evt);
+static void machine_process_ue_event(struct work_struct *work);
+
 static struct irq_work mce_event_process_work = {
         .func = machine_check_process_queued_event,
 };
 
+DECLARE_WORK(mce_ue_event_work, machine_process_ue_event);
+
 static void mce_set_error_info(struct machine_check_event *mce,
                               struct mce_error_info *mce_err)
 {
@@ -143,6 +153,7 @@ void save_mce_event(struct pt_regs *regs, long handled,
                if (phys_addr != ULONG_MAX) {
                        mce->u.ue_error.physical_address_provided = true;
                        mce->u.ue_error.physical_address = phys_addr;
+                       machine_check_ue_event(mce);
                }
        }
        return;
@@ -197,6 +208,26 @@ void release_mce_event(void)
        get_mce_event(NULL, true);
 }
 
+
+/*
+ * Queue up the MCE event which then can be handled later.
+ */
+void machine_check_ue_event(struct machine_check_event *evt)
+{
+       int index;
+
+       index = __this_cpu_inc_return(mce_ue_count) - 1;
+       /* If queue is full, just return for now. */
+       if (index >= MAX_MC_EVT) {
+               __this_cpu_dec(mce_ue_count);
+               return;
+       }
+       memcpy(this_cpu_ptr(&mce_ue_event_queue[index]), evt, sizeof(*evt));
+
+       /* Queue work to process this event later. */
+       schedule_work(&mce_ue_event_work);
+}
+
 /*
  * Queue up the MCE event which then can be handled later.
  */
@@ -219,7 +250,39 @@ void machine_check_queue_event(void)
        /* Queue irq work to process this event later. */
        irq_work_queue(&mce_event_process_work);
 }
-
+/*
+ * process pending MCE event from the mce event queue. This function will be
+ * called during syscall exit.
+ */
+static void machine_process_ue_event(struct work_struct *work)
+{
+       int index;
+       struct machine_check_event *evt;
+
+       while (__this_cpu_read(mce_ue_count) > 0) {
+               index = __this_cpu_read(mce_ue_count) - 1;
+               evt = this_cpu_ptr(&mce_ue_event_queue[index]);
+#ifdef CONFIG_MEMORY_FAILURE
+               /*
+                * This should probably queued elsewhere, but
+                * oh! well
+                */
+               if (evt->error_type == MCE_ERROR_TYPE_UE) {
+                       if (evt->u.ue_error.physical_address_provided) {
+                               unsigned long pfn;
+
+                               pfn = evt->u.ue_error.physical_address >>
+                                       PAGE_SHIFT;
+                               memory_failure(pfn, SIGBUS, 0);
+                       } else
+                               pr_warn("Failed to identify bad address from "
+                                       "where the uncorrectable error (UE) "
+                                       "was generated\n");
+               }
+#endif
+               __this_cpu_dec(mce_ue_count);
+       }
+}
 /*
  * process pending MCE event from the mce event queue. This function will be
  * called during syscall exit.
@@ -227,6 +290,7 @@ void machine_check_queue_event(void)
 static void machine_check_process_queued_event(struct irq_work *work)
 {
        int index;
+       struct machine_check_event *evt;
 
        add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);
 
@@ -236,8 +300,8 @@ static void machine_check_process_queued_event(struct irq_work *work)
         */
        while (__this_cpu_read(mce_queue_count) > 0) {
                index = __this_cpu_read(mce_queue_count) - 1;
-               machine_check_print_event_info(
-                               this_cpu_ptr(&mce_event_queue[index]), false);
+               evt = this_cpu_ptr(&mce_event_queue[index]);
+               machine_check_print_event_info(evt, false);
                __this_cpu_dec(mce_queue_count);
        }
 }