linux-kernel - [PATCH 0/1 RESEND] ARM: plat-versatile: move secondary CPU startup out of .init.

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Message-id: <50A62E92.2080703@huawei.com>
Date:	Fri, 16 Nov 2012 13:16:18 +0100
From:	Claudio Fontana <Claudio.Fontana@...wei.com>
To:	Russell King <linux@....linux.org.uk>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 0/1 RESEND] ARM: plat-versatile: move secondary CPU startup out
 of .init.

Hello,

I am implementing a new feature in QEMU, including virtual CPU hotplug
for the the ARM Cortex A-15 VExpress motherboard.
This new QEMU feature includes a new monitor command "smp_cpus_set",
which allows changing the number of visible CPUs in the guest.

I stumbled upon a limitation in the kernel support for plat-versatile,
which contains the secondary CPU startup code for the VExpress.

Basically, the secondary CPU startup code is preceded by the macro __INIT,
which causes the code to be freed in free_initmem() during kernel_init().

This means that any attempt at hot-booting CPUs in the guest results in
VCPUs jumping to a memory address that was freed, after which the VCPU
behaves erratically, as can be expected.

With this patch applied, we use __CPUINIT instead of __INIT, so that
the right thing happens:
under CONFIG_HOTPLUG_CPU, the secondary CPU startup code is not freed,
the secondary VCPUs start successfully, and it's all gardens and blue skies.

Tested successfully using the ARM fast models for the Cortex-A15.

--
Claudio Fontana (1):
  ARM: plat-versatile: move secondary CPU startup code out of .init.

 arch/arm/plat-versatile/headsmp.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

-- 
1.7.12.1

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