Re: [PATCH v2 10/17] x86/hyperv: implement and use hv_smp_prepare_cpus

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Wei Liu <wei.liu@kernel.org> writes:

> Microsoft Hypervisor requires the root partition to make a few
> hypercalls to setup application processors before they can be used.
>
> Signed-off-by: Lillian Grassin-Drake <ligrassi@microsoft.com>
> Signed-off-by: Sunil Muthuswamy <sunilmut@microsoft.com>
> Co-Developed-by: Lillian Grassin-Drake <ligrassi@microsoft.com>
> Co-Developed-by: Sunil Muthuswamy <sunilmut@microsoft.com>
> Signed-off-by: Wei Liu <wei.liu@kernel.org>
> ---
> CPU hotplug and unplug is not yet supported in this setup, so those
> paths remain untouched.
> ---
>  arch/x86/kernel/cpu/mshyperv.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index f7633e1e4c82..4795e54550e6 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -31,6 +31,7 @@
>  #include <asm/reboot.h>
>  #include <asm/nmi.h>
>  #include <clocksource/hyperv_timer.h>
> +#include <asm/numa.h>
>  
>  struct ms_hyperv_info ms_hyperv;
>  EXPORT_SYMBOL_GPL(ms_hyperv);
> @@ -208,6 +209,30 @@ static void __init hv_smp_prepare_boot_cpu(void)
>  	hv_init_spinlocks();
>  #endif
>  }
> +
> +static void __init hv_smp_prepare_cpus(unsigned int max_cpus)
> +{
> +#if defined(CONFIG_X86_64)

'#ifdef CONFIG_X86_64' is equally good as you can't compile x86_64
support as a module :-)

> +	int i;
> +	int ret;
> +
> +	native_smp_prepare_cpus(max_cpus);
> +

So hypotetically, if hv_root_partition is true but 'ifdef CONFIG_X86_64'
is false, we won't even be doing native_smp_prepare_cpus()? This doesn't
sound right. Either move it outside of #ifdef or put the #ifdef around
'smp_ops.smp_prepare_cpus' assignment too.

> +	for_each_present_cpu(i) {
> +		if (i == 0)
> +			continue;
> +		ret = hv_call_add_logical_proc(numa_cpu_node(i), i, cpu_physical_id(i));
> +		BUG_ON(ret);
> +	}
> +
> +	for_each_present_cpu(i) {
> +		if (i == 0)
> +			continue;
> +		ret = hv_call_create_vp(numa_cpu_node(i), hv_current_partition_id, i, i);
> +		BUG_ON(ret);
> +	}
> +#endif
> +}
>  #endif
>  
>  static void __init ms_hyperv_init_platform(void)
> @@ -364,6 +389,8 @@ static void __init ms_hyperv_init_platform(void)
>  
>  # ifdef CONFIG_SMP
>  	smp_ops.smp_prepare_boot_cpu = hv_smp_prepare_boot_cpu;
> +	if (hv_root_partition)
> +		smp_ops.smp_prepare_cpus = hv_smp_prepare_cpus;
>  # endif
>  
>  	/*

-- 
Vitaly