linux-kernel - Re: [PATCH v5 3/8] KVM: MMU: fast invalidate all pages

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Date:	Fri, 17 May 2013 02:39:07 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	avi.kivity@...il.com, mtosatti@...hat.com, pbonzini@...hat.com,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v5 3/8] KVM: MMU: fast invalidate all pages

On 05/16/2013 11:57 PM, Gleb Natapov wrote:

> One more thought. With current patch if zap_invalid_page() will be
> called second time while another zap_invalid_page() is still running
> (can that happen?) they will both run concurrently fighting for the

Currently, it can not happen since zap_invalid_page is needed when slot
is being deleted which protected by slot-lock.

But we allow it to be concurrent as you commented: we can use it in
->release() instead of calling kvm_mmu_zap_all(), in that case, multiple
call zap_invalid_page() can happen.

> mmu_lock. Is this a problem?

Are you worry about that it can not progress due to lock contention when
walking active_list? Zapping at least 10 pages before releasing the lock
should ensure that it can progress.

Do you see any potential issue?



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