On Tue, 28 Feb 2017 11:27:29 +0530
Mahesh Jagannath Salgaonkar [off-list ref] wrote:

On 02/28/2017 07:30 AM, Nicholas Piggin wrote:

quoted

A synchronous machine check is an exception raised by the attempt to
execute the current instruction. If the error can't be corrected, it
can make sense to SIGBUS the currently running process.

In other cases, the error condition is not related to the current
instruction, so killing the current process is not the right thing to
do.

Today, all machine checks are MCE_SEV_ERROR_SYNC, so this has no
practical change. It will be used to handle POWER9 asynchronous
machine checks.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/platforms/powernv/opal.c | 21 ++++++---------------
 1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index 86d9fde93c17..e0f856bfbfe8 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c

@@ -395,7 +395,6 @@ static int opal_recover_mce(struct pt_regs *regs,
 					struct machine_check_event *evt)
 {
 	int recovered = 0;
-	uint64_t ea = get_mce_fault_addr(evt);

 	if (!(regs->msr & MSR_RI)) {
 		/* If MSR_RI isn't set, we cannot recover */

@@ -404,26 +403,18 @@ static int opal_recover_mce(struct pt_regs *regs,
 	} else if (evt->disposition == MCE_DISPOSITION_RECOVERED) {
 		/* Platform corrected itself */
 		recovered = 1;
-	} else if (ea && !is_kernel_addr(ea)) {
+	} else if (evt->severity == MCE_SEV_FATAL) {
+		/* Fatal machine check */
+		pr_err("Machine check interrupt is fatal\n");
+		recovered = 0;  

Setting recovered = 0 would trigger kernel panic. Should we panic the
kernel for asynchronous errors ?

If it's not recoverable, I don't see what other option we have. SRR0 is
meaningless for async machine checks. So it's much the same thing we do
as if we don't have a process to kill or were running in kernel when a
synchronous MCE occurred.

Thanks,
Nick