[PATCH v2 0/4] sparc64: Jump to boot prom from console on panic

[PATCH v2 0/4] sparc64: Jump to boot prom from console on panic

[Vijay Kumar]

Currently Stop-A (L1A) does not make the kernel switch to OBP on panic. This
patchset addresses this issue. Also, now we can cause a jump to OBP by sending
'break' twice from sunhv console. On bare metal, one can send a break by
typing Esc + 'B' + Sysrq (or whatever). On LDOM, press Ctrl + ] in telnet,
and then "send break" at the telnet prompt.

      sparc64: Set cpu state to offline when stopped
      sparc64: Migrate hvcons irq to panicked cpu
      sparc64: Send break twice from console to return to boot prom
      Documentation/sparc: Steps for sending break on sunhv console

 Documentation/sparc/console.txt |    9 +++++++++
 arch/sparc/include/asm/setup.h  |    1 +
 arch/sparc/kernel/smp_64.c      |    9 ++++++++-
 drivers/tty/serial/sunhv.c      |   12 +++++++++++-
 kernel/panic.c                  |    3 ++-
 5 files changed, 31 insertions(+), 3 deletions(-)
 create mode 100644 Documentation/sparc/console.txt



--
1.7.1

[PATCH v2 1/4] sparc64: Set cpu state to offline when stopped

[Vijay Kumar]

CPU needs to be marked offline before stopping it. When not marked
offline, the xcall receives HV_EWOULDBLOCK and so assumes that not all
CPUs received the message, and retries. After 10000 retries, it finally
fails with fatal mondo timeout.

Signed-off-by: Vijay Kumar <vijay.ac.kumar@oracle.com>
---
 arch/sparc/kernel/smp_64.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
index d3035ba..14138ad 100644
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -1435,6 +1435,7 @@ void __irq_entry smp_receive_signal_client(int irq, struct pt_regs *regs)
 
 static void stop_this_cpu(void *dummy)
 {
+	set_cpu_online(smp_processor_id(), false);
 	prom_stopself();
 }
 
@@ -1446,6 +1447,8 @@ void smp_send_stop(void)
 		for_each_online_cpu(cpu) {
 			if (cpu == smp_processor_id())
 				continue;
+
+			set_cpu_online(cpu, false);
 #ifdef CONFIG_SUN_LDOMS
 			if (ldom_domaining_enabled) {
 				unsigned long hv_err;
-- 
1.7.1

[PATCH v2 2/4] sparc64: Migrate hvcons irq to panicked cpu

[Vijay Kumar]

On panic, all other CPUs are stopped except the one which had
hit panic. To keep console alive, we need to migrate hvcons irq
to panicked CPU.

Signed-off-by: Vijay Kumar <vijay.ac.kumar@oracle.com>
---
 arch/sparc/include/asm/setup.h |    1 +
 arch/sparc/kernel/smp_64.c     |    6 +++++-
 drivers/tty/serial/sunhv.c     |    6 ++++++
 3 files changed, 12 insertions(+), 1 deletions(-)

diff --git a/arch/sparc/include/asm/setup.h b/arch/sparc/include/asm/setup.h
index 29d64b1..41691a5 100644
--- a/arch/sparc/include/asm/setup.h
+++ b/arch/sparc/include/asm/setup.h
@@ -61,6 +61,7 @@ extern atomic_t dcpage_flushes_xcall;
 extern int sysctl_tsb_ratio;
 #endif
 
+void sunhv_migrate_hvcons_irq(int cpu);
 void sun_do_break(void);
 extern int stop_a_enabled;
 extern int scons_pwroff;
diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
index 14138ad..52dc4b7 100644
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -1444,8 +1444,12 @@ void smp_send_stop(void)
 	int cpu;
 
 	if (tlb_type == hypervisor) {
+		int this_cpu = smp_processor_id();
+
+		sunhv_migrate_hvcons_irq(this_cpu);
+
 		for_each_online_cpu(cpu) {
-			if (cpu == smp_processor_id())
+			if (cpu == this_cpu)
 				continue;
 
 			set_cpu_online(cpu, false);
diff --git a/drivers/tty/serial/sunhv.c b/drivers/tty/serial/sunhv.c
index 4e603d0..59828d8 100644
--- a/drivers/tty/serial/sunhv.c
+++ b/drivers/tty/serial/sunhv.c
@@ -398,6 +398,12 @@ static struct uart_driver sunhv_reg = {
 
 static struct uart_port *sunhv_port;
 
+void sunhv_migrate_hvcons_irq(int cpu)
+{
+	/* Migrate hvcons irq to param cpu */
+	irq_force_affinity(sunhv_port->irq, cpumask_of(cpu));
+}
+
 /* Copy 's' into the con_write_page, decoding "\n" into
  * "\r\n" along the way.  We have to return two lengths
  * because the caller needs to know how much to advance
-- 
1.7.1

Re: [PATCH v2 2/4] sparc64: Migrate hvcons irq to panicked cpu

[David Miller]

From: Vijay Kumar <vijay.ac.kumar@oracle.com>
Date: Fri, 11 Nov 2016 10:11:57 -0800

> @@ -1444,8 +1444,12 @@ void smp_send_stop(void)
>  	int cpu;
>  
>  	if (tlb_type == hypervisor) {
> +		int this_cpu = smp_processor_id();
> +
> +		sunhv_migrate_hvcons_irq(this_cpu);
> +

You can't unconditionally call into code that might be configured
out by a Kconfig option, as you are doing here.

If SERIAL_SUNHV=n this change will thus result in a build error.

Re: [PATCH v2 2/4] sparc64: Migrate hvcons irq to panicked cpu

[Vijay Kumar]

On 11/19/2016 9:48 AM, David Miller wrote:
> From: Vijay Kumar <vijay.ac.kumar@oracle.com>
> Date: Fri, 11 Nov 2016 10:11:57 -0800
>
>> @@ -1444,8 +1444,12 @@ void smp_send_stop(void)
>>   	int cpu;
>>   
>>   	if (tlb_type == hypervisor) {
>> +		int this_cpu = smp_processor_id();
>> +
>> +		sunhv_migrate_hvcons_irq(this_cpu);
>> +
> You can't unconditionally call into code that might be configured
> out by a Kconfig option, as you are doing here.
>
> If SERIAL_SUNHV=n this change will thus result in a build error.
Thanks for your comment. I will fix this and send revised version of patch.

Thanks,
Vijay

[PATCH v2 3/4] sparc64: Send break twice from console to return to boot prom

[Vijay Kumar]

Now we can also jump to boot prom from sunhv console by sending
break twice on console for both running and panicked kernel
cases.

Signed-off-by: Vijay Kumar <vijay.ac.kumar@oracle.com>
---
 drivers/tty/serial/sunhv.c |    6 +++++-
 kernel/panic.c             |    3 ++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/sunhv.c b/drivers/tty/serial/sunhv.c
index 59828d8..33c35b4 100644
--- a/drivers/tty/serial/sunhv.c
+++ b/drivers/tty/serial/sunhv.c
@@ -116,7 +116,7 @@ static int receive_chars_getchar(struct uart_port *port)
 
 static int receive_chars_read(struct uart_port *port)
 {
-	int saw_console_brk = 0;
+	static int saw_console_brk;
 	int limit = 10000;
 
 	while (limit-- > 0) {
@@ -128,6 +128,9 @@ static int receive_chars_read(struct uart_port *port)
 			bytes_read = 0;
 
 			if (stat == CON_BREAK) {
+				if (saw_console_brk)
+					sun_do_break();
+
 				if (uart_handle_break(port))
 					continue;
 				saw_console_brk = 1;
@@ -151,6 +154,7 @@ static int receive_chars_read(struct uart_port *port)
 		if (port->sysrq != 0 &&  *con_read_page) {
 			for (i = 0; i < bytes_read; i++)
 				uart_handle_sysrq_char(port, con_read_page[i]);
+			saw_console_brk = 0;
 		}
 
 		if (port->state == NULL)
diff --git a/kernel/panic.c b/kernel/panic.c
index ca8cea1..4fe3b28 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -240,7 +240,8 @@ void panic(const char *fmt, ...)
 		extern int stop_a_enabled;
 		/* Make sure the user can actually press Stop-A (L1-A) */
 		stop_a_enabled = 1;
-		pr_emerg("Press Stop-A (L1-A) to return to the boot prom\n");
+		pr_emerg("Press Stop-A (L1-A) from sun keyboard or send break\n"
+			 "twice on console to return to the boot prom\n");
 	}
 #endif
 #if defined(CONFIG_S390)
-- 
1.7.1

[PATCH v2 4/4] Documentation/sparc: Steps for sending break on sunhv console

[Vijay Kumar]

Documented the steps for sending break on sunhv console.

Signed-off-by: Vijay Kumar <vijay.ac.kumar@oracle.com>
---
 Documentation/sparc/console.txt |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/Documentation/sparc/console.txt b/Documentation/sparc/console.txt
new file mode 100644
index 0000000..ab55353
--- /dev/null
+++ b/Documentation/sparc/console.txt
@@ -0,0 +1,9 @@
+Steps for sending 'break' on sunhv console:
+===========================================
+
+On Baremetal:
+   1. press   Esc + 'B'
+
+On LDOM:
+   1. press    Ctrl + ']'
+   2. telnet> send  break	
-- 
1.7.1