linux-kernel - Re: [PATCH RFC v6 10/11] pvqspinlock, x86: Enable qspinlock PV support for KVM

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Date:	Mon, 17 Mar 2014 13:47:30 -0400
From:	Waiman Long <waiman.long@...com>
To:	Paolo Bonzini <pbonzini@...hat.com>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	kvm@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
	virtualization@...ts.linux-foundation.org,
	Andi Kleen <andi@...stfloor.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Michel Lespinasse <walken@...gle.com>,
	Alok Kataria <akataria@...are.com>, linux-arch@...r.kernel.org,
	Gleb Natapov <gleb@...hat.com>, x86@...nel.org,
	Ingo Molnar <mingo@...hat.com>, xen-devel@...ts.xenproject.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Arnd Bergmann <arnd@...db.de>,
	Scott J Norton <scott.norton@...com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Chris Wright <chrisw@...s-sol.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Aswin Chandramouleeswaran <aswin@...com>,
	Chegu Vinod <chegu_vinod@...com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v6 10/11] pvqspinlock, x86: Enable qspinlock PV support
 for KVM

On 03/14/2014 04:42 AM, Paolo Bonzini wrote:
> Il 13/03/2014 20:13, Waiman Long ha scritto:
>>>>
>>>
>>> This should also disable the unfair path.
>>>
>>> Paolo
>>>
>>
>> The unfair lock uses a different jump label and does not require any
>> special PV ops. There is a separate init function for that.
>
> Yeah, what I mean is that the patches that enable paravirtualization 
> should also take care of decreasing the unfair-lock jump label when 
> paravirtualization is enabled.
>
> Paolo

As there are people who don't like unfair lock at all, I prefer to give 
them the option to turn this on or off instead of forcing them to always 
use unfair lock in a PV guest.

-Longman
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