linux-kernel - Re: [PATCH v7 06/11] pvqspinlock, x86: Allow unfair queue spinlock in a KVM guest

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Date:	Thu, 20 Mar 2014 23:01:39 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Waiman Long <Waiman.Long@...com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>,
	Peter Zijlstra <peterz@...radead.org>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
	Andi Kleen <andi@...stfloor.org>,
	Michel Lespinasse <walken@...gle.com>,
	Alok Kataria <akataria@...are.com>, linux-arch@...r.kernel.org,
	Gleb Natapov <gleb@...hat.com>, x86@...nel.org,
	xen-devel@...ts.xenproject.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Scott J Norton <scott.norton@...com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Steven Rostedt <rostedt@...dmis.org>,
	Chris Wright <chrisw@...s-sol.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Aswin Chandramouleeswaran <aswin@...com>,
	Chegu Vinod <chegu_vinod@...com>, linux-kernel@...r.kernel.org,
	David Vrabel <david.vrabel@...rix.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v7 06/11] pvqspinlock, x86: Allow unfair queue spinlock
 in a KVM guest

Il 19/03/2014 21:14, 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@...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
>

No!  Please do what I asked you to do.  You are not handling Hyper-V or 
VMWare.  Just use X86_FEATURE_HYPERVISOR and it will cover all 
hypervisors that actually follow Intel's guidelines.

Paolo
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