linux-kernel - Re: [PATCH v3 13/15] KVM: MMU: locklessly write-protect the page

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Date:	Thu, 24 Oct 2013 12:32:33 +0300
From:	Gleb Natapov <gleb@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc:	avi.kivity@...il.com, mtosatti@...hat.com, pbonzini@...hat.com,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v3 13/15] KVM: MMU: locklessly write-protect the page

On Thu, Oct 24, 2013 at 05:24:12PM +0800, Xiao Guangrong wrote:
> On 10/24/2013 05:17 PM, Gleb Natapov wrote:
> 
> >>  
> >> -/**
> >> - * kvm_mmu_write_protect_pt_masked - write protect selected PT level pages
> >> +static void __rmap_write_protect_lockless(u64 *sptep)
> >> +{
> >> +	u64 spte;
> >> +
> >> +retry:
> >> +	/*
> >> +	 * Note we may partly read the sptep on 32bit host, however, we
> >> +	 * allow this case because:
> >> +	 * - we do not access the page got from the sptep.
> >> +	 * - cmpxchg64 can detect that case and avoid setting a wrong value
> >> +	 *   to the sptep.
> >> +	 */
> >> +	spte = *rcu_dereference(sptep);
> >> +	if (unlikely(!is_last_spte(spte) || !is_writable_pte(spte)))
> > is_last_spte gets two parameters.
> 
> In patch [PATCH v3 12/15] KVM: MMU: check last spte with unawareness of mapping level,
> we have removed the 'level' from the parameter list.
Ah, I haven't got 12/15 and git am did not complain :(

--
			Gleb.
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