Hello, I am implementing virtual CPU hotplug for the the ARM Cortex A-15 VExpress motherboard. This is mainly a QEMU feature, which allows dynamically changing the number of 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
