[PATCH] powerpc/powernv: Add a kmsg_dumper that flushes console output on panic
Russell Currey
ruscur at russell.cc
Tue Nov 24 14:26:33 AEDT 2015
On BMC machines, console output is controlled by the OPAL firmware and is
only flushed when its pollers are called. When the kernel is in a panic
state, it no longer calls these pollers and thus console output does not
completely flush, causing some output from the panic to be lost.
This patch adds a new kmsg_dumper which gets called at panic time to ensure
panic output is not lost. It accomplishes this by calling OPAL_CONSOLE_FLUSH
in the OPAL API, and if that is not available, the pollers are called enough
times to (hopefully) completely flush the buffer.
Signed-off-by: Russell Currey <ruscur at russell.cc>
---
A patch to add the preferred OPAL call for flushing the console buffer,
OPAL_CONSOLE_FLUSH, was recently sent upstream to Skiboot. You can track
its progress here: https://patchwork.ozlabs.org/patch/547379/
---
arch/powerpc/include/asm/opal-api.h | 3 +-
arch/powerpc/include/asm/opal.h | 3 ++
arch/powerpc/platforms/powernv/Makefile | 1 +
arch/powerpc/platforms/powernv/opal-kmsg.c | 70 ++++++++++++++++++++++++++
arch/powerpc/platforms/powernv/opal-wrappers.S | 1 +
arch/powerpc/platforms/powernv/opal.c | 3 ++
6 files changed, 80 insertions(+), 1 deletion(-)
create mode 100644 arch/powerpc/platforms/powernv/opal-kmsg.c
diff --git a/arch/powerpc/include/asm/opal-api.h b/arch/powerpc/include/asm/opal-api.h
index 8374afe..f8faaae 100644
--- a/arch/powerpc/include/asm/opal-api.h
+++ b/arch/powerpc/include/asm/opal-api.h
@@ -157,7 +157,8 @@
#define OPAL_LEDS_GET_INDICATOR 114
#define OPAL_LEDS_SET_INDICATOR 115
#define OPAL_CEC_REBOOT2 116
-#define OPAL_LAST 116
+#define OPAL_CONSOLE_FLUSH 117
+#define OPAL_LAST 117
/* Device tree flags */
diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index 8001159..a5fd407 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -35,6 +35,7 @@ int64_t opal_console_read(int64_t term_number, __be64 *length,
uint8_t *buffer);
int64_t opal_console_write_buffer_space(int64_t term_number,
__be64 *length);
+void opal_console_flush(void);
int64_t opal_rtc_read(__be32 *year_month_day,
__be64 *hour_minute_second_millisecond);
int64_t opal_rtc_write(uint32_t year_month_day,
@@ -262,6 +263,8 @@ extern int opal_resync_timebase(void);
extern void opal_lpc_init(void);
+extern void opal_kmsg_init(void);
+
extern int opal_event_request(unsigned int opal_event_nr);
struct opal_sg_list *opal_vmalloc_to_sg_list(void *vmalloc_addr,
diff --git a/arch/powerpc/platforms/powernv/Makefile b/arch/powerpc/platforms/powernv/Makefile
index 1c8cdb6..b9de7ef 100644
--- a/arch/powerpc/platforms/powernv/Makefile
+++ b/arch/powerpc/platforms/powernv/Makefile
@@ -2,6 +2,7 @@ obj-y += setup.o opal-wrappers.o opal.o opal-async.o idle.o
obj-y += opal-rtc.o opal-nvram.o opal-lpc.o opal-flash.o
obj-y += rng.o opal-elog.o opal-dump.o opal-sysparam.o opal-sensor.o
obj-y += opal-msglog.o opal-hmi.o opal-power.o opal-irqchip.o
+obj-y += opal-kmsg.o
obj-$(CONFIG_SMP) += smp.o subcore.o subcore-asm.o
obj-$(CONFIG_PCI) += pci.o pci-p5ioc2.o pci-ioda.o
diff --git a/arch/powerpc/platforms/powernv/opal-kmsg.c b/arch/powerpc/platforms/powernv/opal-kmsg.c
new file mode 100644
index 0000000..904f123
--- /dev/null
+++ b/arch/powerpc/platforms/powernv/opal-kmsg.c
@@ -0,0 +1,70 @@
+/*
+ * kmsg dumper that ensures the OPAL console fully flushes panic messages
+ *
+ * Author: Russell Currey <ruscur at russell.cc>
+ *
+ * Copyright 2015 IBM Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+
+#include <linux/kmsg_dump.h>
+
+#include <asm/opal.h>
+#include <asm/opal-api.h>
+
+/*
+ * Console output is controlled by OPAL firmware. The kernel regularly calls
+ * OPAL_POLL_EVENTS, which flushes some console output. In a panic state,
+ * however, the kernel no longer calls OPAL_POLL_EVENTS and the panic message
+ * may not be completely printed. This function does not actually dump the
+ * message, it just ensures that OPAL completely flushes the console buffer.
+ */
+static void force_opal_console_flush(struct kmsg_dumper *dumper,
+ enum kmsg_dump_reason reason)
+{
+ int i;
+
+ /*
+ * Outside of a panic context the pollers will continue to run,
+ * so we don't need to do any special flushing.
+ */
+ if (reason != KMSG_DUMP_PANIC) {
+ return;
+ }
+
+ if (opal_check_token(OPAL_CONSOLE_FLUSH)) {
+ opal_console_flush();
+ } else {
+ /*
+ * If OPAL_CONSOLE_FLUSH is not implemented in the firmware,
+ * the console can still be flushed by calling the polling
+ * function enough times to flush the buffer. We don't know
+ * how much output still needs to be flushed, but we can be
+ * generous since the kernel is in panic and doesn't need
+ * to do much else.
+ */
+ printk(KERN_NOTICE "opal: OPAL_CONSOLE_FLUSH missing.\n");
+ for (i = 0; i < 1024; i++) {
+ opal_poll_events(NULL);
+ }
+ }
+}
+
+static struct kmsg_dumper opal_kmsg_dumper = {
+ .dump = force_opal_console_flush
+};
+
+void __init opal_kmsg_init(void)
+{
+ int rc;
+
+ /* Add our dumper to the list */
+ rc = kmsg_dump_register(&opal_kmsg_dumper);
+ if (rc != 0) {
+ pr_err("opal: kmsg_dump_register failed; returned %d\n", rc);
+ }
+}
diff --git a/arch/powerpc/platforms/powernv/opal-wrappers.S b/arch/powerpc/platforms/powernv/opal-wrappers.S
index b7a464f..e45b88a 100644
--- a/arch/powerpc/platforms/powernv/opal-wrappers.S
+++ b/arch/powerpc/platforms/powernv/opal-wrappers.S
@@ -301,3 +301,4 @@ OPAL_CALL(opal_flash_erase, OPAL_FLASH_ERASE);
OPAL_CALL(opal_prd_msg, OPAL_PRD_MSG);
OPAL_CALL(opal_leds_get_ind, OPAL_LEDS_GET_INDICATOR);
OPAL_CALL(opal_leds_set_ind, OPAL_LEDS_SET_INDICATOR);
+OPAL_CALL(opal_console_flush, OPAL_CONSOLE_FLUSH);
diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index 4296d55..a94a85c 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -758,6 +758,9 @@ static int __init opal_init(void)
opal_pdev_init(opal_node, "ibm,opal-flash");
opal_pdev_init(opal_node, "ibm,opal-prd");
+ /* Initialise OPAL kmsg dumper for flushing console on panic */
+ opal_kmsg_init();
+
return 0;
}
machine_subsys_initcall(powernv, opal_init);
--
2.6.2
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