linux-kernel - [PATCH] powerpc/fadump: update kernel logs before fadump crash begins

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Date:   Sat,  6 Jun 2020 10:15:06 +0530
From:   Sourabh Jain <sourabhjain@...ux.ibm.com>
To:     mpe@...erman.id.au
Cc:     hbathini@...ux.ibm.com, mahesh@...ux.vnet.ibm.com,
        linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org
Subject: [PATCH] powerpc/fadump: update kernel logs before fadump crash begins

When we hit the fadump crash via the panic path the pstore update is
missing. This is observed when commit 8341f2f222d7 ("sysrq: Use panic()
to force a crash") changed the sysrq-trigger to take panic path instead
of die path.

The PPC panic event handler addresses the system panic in two different
ways based on the system configuration. It first allows the FADump (if
configured) to handle the kernel panic else forwards the call to platform
specific panic function. Now pstore update is missing only if FADump
handles the kernel panic, the platform-specific panic function do update
the pstore by calling panic_flush_kmsg_end function.

The simplest approach to handle this issue is to add pstore update in PPC
panic handler before FADump handles the panic. But this leads to multiple
pstore updates in case FADump is not configured and platform-specific
panic function serves the kernel panic.

Hence the function panic_flush_kmsg_end (used by the platform-specific
panic function to update the kernel logs) is split into two functions, one
will update the pstore (called in ppc panic event handler) and others will
flush the kmsg on the console (called in platform specific panic function).

Signed-off-by: Sourabh Jain <sourabhjain@...ux.ibm.com>
---
 arch/powerpc/include/asm/bug.h         |  2 ++
 arch/powerpc/kernel/setup-common.c     |  1 +
 arch/powerpc/kernel/traps.c            | 12 +++++++++++-
 arch/powerpc/platforms/ps3/setup.c     |  2 +-
 arch/powerpc/platforms/pseries/setup.c |  2 +-
 5 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
index 338f36cd9934..9268551a69bc 100644
--- a/arch/powerpc/include/asm/bug.h
+++ b/arch/powerpc/include/asm/bug.h
@@ -118,6 +118,8 @@ extern void _exception_pkey(struct pt_regs *, unsigned long, int);
 extern void die(const char *, struct pt_regs *, long);
 extern bool die_will_crash(void);
 extern void panic_flush_kmsg_start(void);
+extern void panic_flush_kmsg_dump(void);
+extern void panic_flush_kmsg_console(void);
 extern void panic_flush_kmsg_end(void);
 #endif /* !__ASSEMBLY__ */
 
diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
index 7f8c890360fe..2d546a9e8bb1 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -699,6 +699,7 @@ static int ppc_panic_event(struct notifier_block *this,
 	 * want interrupts to be hard disabled.
 	 */
 	hard_irq_disable();
+	panic_flush_kmsg_dump();
 
 	/*
 	 * If firmware-assisted dump has been registered then trigger
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 82a3438300fd..bb6bc19992b3 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -169,15 +169,25 @@ extern void panic_flush_kmsg_start(void)
 	bust_spinlocks(1);
 }
 
-extern void panic_flush_kmsg_end(void)
+extern void panic_flush_kmsg_dump(void)
 {
 	printk_safe_flush_on_panic();
 	kmsg_dump(KMSG_DUMP_PANIC);
+}
+
+extern void panic_flush_kmsg_console(void)
+{
 	bust_spinlocks(0);
 	debug_locks_off();
 	console_flush_on_panic(CONSOLE_FLUSH_PENDING);
 }
 
+extern void panic_flush_kmsg_end(void)
+{
+	panic_flush_kmsg_dump();
+	panic_flush_kmsg_console();
+}
+
 static unsigned long oops_begin(struct pt_regs *regs)
 {
 	int cpu;
diff --git a/arch/powerpc/platforms/ps3/setup.c b/arch/powerpc/platforms/ps3/setup.c
index b29368931c56..f96ba34284a1 100644
--- a/arch/powerpc/platforms/ps3/setup.c
+++ b/arch/powerpc/platforms/ps3/setup.c
@@ -101,7 +101,7 @@ static void ps3_panic(char *str)
 	printk("   System does not reboot automatically.\n");
 	printk("   Please press POWER button.\n");
 	printk("\n");
-	panic_flush_kmsg_end();
+	panic_flush_kmsg_console();
 
 	while(1)
 		lv1_pause(1);
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 0c8421dd01ab..66ecb88c4b8e 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -788,7 +788,7 @@ static void __init pSeries_setup_arch(void)
 
 static void pseries_panic(char *str)
 {
-	panic_flush_kmsg_end();
+	panic_flush_kmsg_console();
 	rtas_os_term(str);
 }
 
-- 
2.25.4