linux-kernel - Re: [PATCH] KVM: x86: Convert tsc_write_lock to raw

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Message-ID: <4D502AA5.7040407@siemens.com>
Date:	Mon, 07 Feb 2011 18:23:49 +0100
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Zachary Amsden <zamsden@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	kvm <kvm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KVM: x86: Convert tsc_write_lock to raw_spinlock

On 2011-02-07 18:10, Avi Kivity wrote:
> On 02/07/2011 06:59 PM, Jan Kiszka wrote:
>>>
>>>  (well, actually, cpufreq_notifier and kvm_arch_hardware_enable are
>>>  already non preemptible, and the stats code should just go away?)
>>
>> The stats code is trivial to convert, so it doesn't matter.
> 
> Removal is easier.

Is that stat interface no longer used?

> 
>> But what about mmu_shrink and its list_move_tail? How is this
>> synchronized against kvm_destroy_vm - already today?
> 
> kvm_destroy_vm() takes kvm_lock.  If a vm is destroyed before 
> mmu_shrink(), mmu_shrink() will never see it.  If we reach mmu_shrink() 
> before kvm_destroy_vm(), the latter will wait until mmu_shrink() is done.
> 

Ah, I was confused. Would require some more logic if we wanted to make
the loop lock-less, though.

Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
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