linux-kernel - Re: [PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check

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Message-Id: <577CDAF3.4030401@linux.vnet.ibm.com>
Date:	Wed, 06 Jul 2016 18:18:27 +0800
From:	xinhui <xinhui.pan@...ux.vnet.ibm.com>
To:	Wanpeng Li <kernellwp@...il.com>,
	Peter Zijlstra <peterz@...radead.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linuxppc-dev@...ts.ozlabs.org,
	virtualization@...ts.linux-foundation.org,
	linux-s390 <linux-s390@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>, mpe@...erman.id.au,
	Paul Mackerras <paulus@...ba.org>, benh@...nel.crashing.org,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Waiman Long <waiman.long@....com>, will.deacon@....com,
	boqun.feng@...il.com, Davidlohr Bueso <dave@...olabs.net>,
	schwidefsky@...ibm.com, Paolo Bonzini <pbonzini@...hat.com>,
	kvm <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check


On 2016年07月06日 16:32, Wanpeng Li wrote:
> 2016-07-06 15:58 GMT+08:00 Peter Zijlstra <peterz@...radead.org>:
>> On Wed, Jul 06, 2016 at 02:46:34PM +0800, Wanpeng Li wrote:
>>>> SO it's easy for ppc to implement such interface. Note that yield_count is
>>>> set by powerVM/KVM.
>>>> and only pSeries can run a guest for now. :)
>>>>
>>>> I also review x86 related code, looks like we need add one hyer-call to get
>>>> such vcpu preemption info?
>>>
>>> There is no such stuff to record lock holder in x86 kvm, maybe we
>>> don't need to depend on PLE handler algorithm to guess it if we can
>>> know lock holder vCPU directly.
>>
>> x86/kvm has vcpu->preempted to indicate if a vcpu is currently preempted
>> or not. I'm just not sure if that is visible to the guest or how to make
>> it so.
>
> Yeah, I miss it. I can be the volunteer to do it if there is any idea,
> ping Paolo. :)
>
glad to know that. :)


> Regards,
> Wanpeng Li
>