powerpc/pseries: Handle UE event for memcpy_mcsafe

memcpy_mcsafe has been implemented for power machines which is used
by pmem infrastructure, so that an UE encountered during memcpy from
pmem devices would not result in panic instead a right error code
is returned. The implementation expects machine check handler to ignore
the event and set nip to continue the execution from fixup code.

Appropriate changes are already made to powernv machine check handler,
make similar changes to pseries machine check handler to ignore the
the event and set nip to continue execution at the fixup entry if we
hit UE at an instruction with a fixup entry.

while we are at it, have a common function which searches the exception
table entry and updates nip with fixup address, and any future common
changes can be made in this function that are valid for both architectures.

powernv changes are made by
commit 895e3dce ("powerpc/mce: Handle UE event for memcpy_mcsafe")
Reviewed-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Reviewed-by: Santosh S <santosh@fossix.org>
Signed-off-by: Ganesh Goudar <ganeshgr@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200326184916.31172-1-ganeshgr@linux.ibm.com

arch/powerpc/include/asm/mce.h

@@ -218,6 +218,8 @@ extern void machine_check_queue_event(void);
 extern void machine_check_print_event_info(struct machine_check_event *evt,
 					   bool user_mode, bool in_guest);
 unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr);
+extern void mce_common_process_ue(struct pt_regs *regs,
+				  struct mce_error_info *mce_err);
 #ifdef CONFIG_PPC_BOOK3S_64
 void flush_and_reload_slb(void);
 #endif /* CONFIG_PPC_BOOK3S_64 */

arch/powerpc/kernel/mce.c

@@ -15,6 +15,7 @@
 #include <linux/percpu.h>
 #include <linux/export.h>
 #include <linux/irq_work.h>
+#include <linux/extable.h>
 
 #include <asm/machdep.h>
 #include <asm/mce.h>
@@ -251,6 +252,19 @@ void machine_check_queue_event(void)
 	/* Queue irq work to process this event later. */
 	irq_work_queue(&mce_event_process_work);
 }
+
+void mce_common_process_ue(struct pt_regs *regs,
+			   struct mce_error_info *mce_err)
+{
+	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);
+	}
+}
+
 /*
  * process pending MCE event from the mce event queue. This function will be
  * called during syscall exit.

arch/powerpc/kernel/mce_power.c

@@ -579,14 +579,10 @@ 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);
+	mce_common_process_ue(regs, mce_err);
+	if (mce_err->ignore_event)
 		return 1;
-	}
 
 	/*
 	 * On specific SCOM read via MMIO we may get a machine check

arch/powerpc/platforms/pseries/ras.c

@@ -558,6 +558,9 @@ static int mce_handle_error(struct pt_regs *regs, struct rtas_error_log *errp)
 	switch (mce_log->error_type) {
 	case MC_ERROR_TYPE_UE:
 		mce_err.error_type = MCE_ERROR_TYPE_UE;
+		mce_common_process_ue(regs, &mce_err);
+		if (mce_err.ignore_event)
+			disposition = RTAS_DISP_FULLY_RECOVERED;
 		switch (err_sub_type) {
 		case MC_ERROR_UE_IFETCH:
 			mce_err.u.ue_error_type = MCE_UE_ERROR_IFETCH;