Re: [PATCH v7 3/6] x86/topology: Disable CPU online/offline control for TDX guest

[Sathyanarayanan Kuppuswamy]

On 10/17/21 12:23 PM, Thomas Gleixner wrote:
> Seriously? This lets the unplug start, which starts to kick off tasks
> from the CPU just to make it fail a few steps later?
>
> The obvious place to prevent this is the CPU hotplug code itself, right?
>
> Thanks,
>
>          tglx
> ---
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index 192e43a87407..c544eb6c79d3 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -1178,6 +1178,8 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
>   
>   static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
>   {
> +	if (cc_platform_has(CC_HOTPLUG_DISABLED))
> +		return -ENOTSUPP;
>   	if (cpu_hotplug_disabled)
>   		return -EBUSY;
>   	return _cpu_down(cpu, 0, target);

Makes sense. I will use it in next version.

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer