Re: [PATCH RFC v5 5/8] pvqspinlock, x86: Enable unfair queue spinlock in a KVM guest

[Paolo Bonzini <pbonzini@redhat.com>]

Il 26/02/2014 16:14, Waiman Long ha scritto:
> This patch adds a KVM init function to activate the unfair queue
> spinlock in a KVM guest when the PARAVIRT_UNFAIR_LOCKS kernel config
> option is selected.
>
> Signed-off-by: Waiman Long <Waiman.Long@hp.com>
> ---
>  arch/x86/kernel/kvm.c |   17 +++++++++++++++++
>  1 files changed, 17 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 713f1b3..a489140 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -826,3 +826,20 @@ static __init int kvm_spinlock_init_jump(void)
>  early_initcall(kvm_spinlock_init_jump);
>
>  #endif	/* CONFIG_PARAVIRT_SPINLOCKS */
> +
> +#ifdef CONFIG_PARAVIRT_UNFAIR_LOCKS
> +/*
> + * Enable unfair lock if running in a real para-virtualized environment
> + */
> +static __init int kvm_unfair_locks_init_jump(void)
> +{
> +	if (!kvm_para_available())
> +		return 0;
> +
> +	static_key_slow_inc(&paravirt_unfairlocks_enabled);
> +	printk(KERN_INFO "KVM setup unfair spinlock\n");
> +
> +	return 0;
> +}
> +early_initcall(kvm_unfair_locks_init_jump);
> +#endif
>

I think this should apply to all paravirt implementations, unless 
pv_lock_ops.kick_cpu != NULL.

Paolo