[RFC PATCH 0/5] arm64: initial CPU_HOTPLUG support

[Mark Rutland]

On Thu, Jul 11, 2013 at 04:10:51PM +0100, Hanjun Guo wrote:
> Hi Mark,

Hi Hanjun,

> 
> I tested this patch set on the armv8 foundation model, it's panic.
> 
> I seems that we need to do something more, I'll also checkout
> what's going on here.
> 
> Thanks
> Hanjun
> 
> dump formation:
> root at genericarmv8:/sys/devices/system/cpu/cpu3# echo 0 > online
> CPU3: Booted secondary processor
> CPU3: shutdown
> BUG: failure at kernel/time/clockevents.c:284/clockevents_register_device()!
> Kernel panic - not syncing: BUG!
> CPU: 3 PID: 0 Comm: swapper/3 Not tainted 3.10.0+ #2
> Call trace:
> [<ffffffc0000873e0>] dump_backtrace+0x0/0x12c
> [<ffffffc000087520>] show_stack+0x14/0x1c
> [<ffffffc0003f2e7c>] dump_stack+0x20/0x28
> [<ffffffc0003efd24>] panic+0xe8/0x214
> [<ffffffc0000d049c>] clockevents_set_mode+0x0/0x6c
> [<ffffffc0000d074c>] clockevents_config_and_register+0x24/0x30
> [<ffffffc0003ef840>] arch_timer_setup+0xd8/0x140
> [<ffffffc0003ef8f0>] arch_timer_cpu_notify+0x48/0xc8
> [<ffffffc0000b83e4>] notifier_call_chain+0x48/0x88
> [<ffffffc0000b8500>] __raw_notifier_call_chain+0xc/0x14
> [<ffffffc0000973f0>] __cpu_notify+0x30/0x58
> [<ffffffc00009742c>] cpu_notify+0x14/0x1c
> [<ffffffc0003ed46c>] notify_cpu_starting+0x14/0x1c
> [<ffffffc0003ece74>] secondary_start_kernel+0xc0/0xf4

That looks suspicious. It looks like the CPU didn't actually die and jumped
immediately to secondary_start_kernel. At a guess, did you update your dts with
a psci node and cpu enable-methods?

I can see the code's broken if you try hotplug with spin-table, because
cpu_disable and cpu_die are both NULL, and the sanity checking doesn't attempt
to deal with this case, so the cpu will end up getting into cpu_die, won't call
anything, and jump straight back into the kernel. I'll fix up the
op_cpu_disable checks to cover this.

The other possibility is that you're using PSCI but your function id for
cpu_off is wrong, and thus the psci cpu_off call fails. Did you update your dts
for PSCI? Below is a patch to do so.

Thanks,
Mark.

---->8----
>From ae35ce871b52ee006f8c5538b9be6c6829a71d6f Mon Sep 17 00:00:00 2001
From: Mark Rutland <mark.rutland at arm.com>
Date: Thu, 11 Jul 2013 17:09:56 +0100
Subject: [PATCH] HACK: arm64: dts: foundation: add PSCI data

---
 arch/arm64/boot/dts/foundation-v8.dts |   19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/boot/dts/foundation-v8.dts b/arch/arm64/boot/dts/foundation-v8.dts
index 84fcc50..335a88f 100644
--- a/arch/arm64/boot/dts/foundation-v8.dts
+++ b/arch/arm64/boot/dts/foundation-v8.dts
@@ -22,6 +22,13 @@
 		serial3 = &v2m_serial3;
 	};
 
+	psci {
+		compatible = "arm,psci";
+		method = "smc";
+		cpu_off = <0x84000001>;
+		cpu_on = <0x84000002>;
+	};
+
 	cpus {
 		#address-cells = <2>;
 		#size-cells = <0>;
@@ -30,29 +37,25 @@
 			device_type = "cpu";
 			compatible = "arm,armv8";
 			reg = <0x0 0x0>;
-			enable-method = "spin-table";
-			cpu-release-addr = <0x0 0x8000fff8>;
+			enable-method = "psci";
 		};
 		cpu at 1 {
 			device_type = "cpu";
 			compatible = "arm,armv8";
 			reg = <0x0 0x1>;
-			enable-method = "spin-table";
-			cpu-release-addr = <0x0 0x8000fff8>;
+			enable-method = "psci";
 		};
 		cpu at 2 {
 			device_type = "cpu";
 			compatible = "arm,armv8";
 			reg = <0x0 0x2>;
-			enable-method = "spin-table";
-			cpu-release-addr = <0x0 0x8000fff8>;
+			enable-method = "psci";
 		};
 		cpu at 3 {
 			device_type = "cpu";
 			compatible = "arm,armv8";
 			reg = <0x0 0x3>;
-			enable-method = "spin-table";
-			cpu-release-addr = <0x0 0x8000fff8>;
+			enable-method = "psci";
 		};
 	};
 
-- 
1.7.9.5