[PATCH v7 6/7] powerpc/mce: Handle UE event for memcpy_mcsafe

[Santosh Sivaraj]

If we take a UE on one of the instructions with a fixup entry, set nip
to continue execution at the fixup entry. Stop processing the event
further or print it.

Based-on-patch-by: Reza Arbab <arbab@xxxxxxxxxxxxx>
Cc: Reza Arbab <arbab@xxxxxxxxxxxxx>
Cc: Mahesh Salgaonkar <mahesh@xxxxxxxxxxxxx>
Signed-off-by: Santosh Sivaraj <santosh@xxxxxxxxxx>
---
 arch/powerpc/include/asm/mce.h  |  4 +++-
 arch/powerpc/kernel/mce.c       | 13 +++++++++++--
 arch/powerpc/kernel/mce_power.c | 15 +++++++++++++--
 3 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/mce.h b/arch/powerpc/include/asm/mce.h
index f3a6036b6bc0..e1931c8c2743 100644
--- a/arch/powerpc/include/asm/mce.h
+++ b/arch/powerpc/include/asm/mce.h
@@ -122,7 +122,8 @@ struct machine_check_event {
 			enum MCE_UeErrorType ue_error_type:8;
 			u8		effective_address_provided;
 			u8		physical_address_provided;
-			u8		reserved_1[5];
+			u8		ignore_event;
+			u8		reserved_1[4];
 			u64		effective_address;
 			u64		physical_address;
 			u8		reserved_2[8];
@@ -193,6 +194,7 @@ struct mce_error_info {
 	enum MCE_Initiator	initiator:8;
 	enum MCE_ErrorClass	error_class:8;
 	bool			sync_error;
+	bool			ignore_event;
 };
 
 #define MAX_MC_EVT	100
diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index 8c0b471658a7..7a9a0bf6d614 100644
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -144,6 +144,7 @@ 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;
+			mce->u.ue_error.ignore_event = mce_err->ignore_event;
 		}
 	}
 	return;
@@ -256,8 +257,13 @@ static void machine_process_ue_event(struct work_struct *work)
 		/*
 		 * This should probably queued elsewhere, but
 		 * oh! well
+		 *
+		 * Don't report this machine check because the caller has a
+		 * asked us to ignore the event, it has a fixup handler which
+		 * will do the appropriate error handling and reporting.
 		 */
-		if (evt->error_type == MCE_ERROR_TYPE_UE) {
+		if (evt->error_type == MCE_ERROR_TYPE_UE &&
+		    !evt->u.ue_error.ignore_event) {
 			if (evt->u.ue_error.physical_address_provided) {
 				unsigned long pfn;
 
@@ -291,8 +297,11 @@ static void machine_check_process_queued_event(struct irq_work *work)
 		index = __this_cpu_read(mce_queue_count) - 1;
 		evt = this_cpu_ptr(&mce_event_queue[index]);
 
-		if (evt->error_type == MCE_ERROR_TYPE_UE)
+		if (evt->error_type == MCE_ERROR_TYPE_UE) {
 			machine_check_ue_event(evt);
+			if (evt->u.ue_error.ignore_event)
+				return;
+		}
 
 		machine_check_print_event_info(evt, false, false);
 		__this_cpu_dec(mce_queue_count);
diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
index bed38a8e2e50..36ca45bbb273 100644
--- a/arch/powerpc/kernel/mce_power.c
+++ b/arch/powerpc/kernel/mce_power.c
@@ -11,6 +11,7 @@
 
 #include <linux/types.h>
 #include <linux/ptrace.h>
+#include <linux/extable.h>
 #include <asm/mmu.h>
 #include <asm/mce.h>
 #include <asm/machdep.h>
@@ -18,6 +19,7 @@
 #include <asm/pte-walk.h>
 #include <asm/sstep.h>
 #include <asm/exception-64s.h>
+#include <asm/extable.h>
 
 /*
  * Convert an address related to an mm to a physical address.
@@ -558,9 +560,18 @@ static int mce_handle_derror(struct pt_regs *regs,
 	return 0;
 }
 
-static long mce_handle_ue_error(struct pt_regs *regs)
+static long mce_handle_ue_error(struct pt_regs *regs,
+				struct mce_error_info *mce_err)
 {
 	long handled = 0;
+	const struct exception_table_entry *entry;
+
+	entry = search_kernel_exception_table(regs->nip);
+	if (entry) {
+		mce_err->ignore_event = true;
+		regs->nip = extable_fixup(entry);
+		return 1;
+	}
 
 	/*
 	 * On specific SCOM read via MMIO we may get a machine check
@@ -593,7 +604,7 @@ static long mce_handle_error(struct pt_regs *regs,
 				&phys_addr);
 
 	if (!handled && mce_err.error_type == MCE_ERROR_TYPE_UE)
-		handled = mce_handle_ue_error(regs);
+		handled = mce_handle_ue_error(regs, &mce_err);
 
 	save_mce_event(regs, handled, &mce_err, regs->nip, addr, phys_addr);
 
-- 
2.20.1