linux-kernel - Re: [PATCH 05/10] KVM: x86: MMU: Use for_each_rmap_spte macro instead of pte_list

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Date:	Tue, 17 Nov 2015 18:58:42 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Takuya Yoshikawa <yoshikawa_takuya_b1@....ntt.co.jp>,
	Marcelo Tosatti <mtosatti@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/10] KVM: x86: MMU: Use for_each_rmap_spte macro instead
 of pte_list_walk()



On 16/11/2015 03:51, Takuya Yoshikawa wrote:
> What kvm_mmu_mark_parents_unsync() does is:
> 
>   for each p_i in sp->parent_ptes rmap chain
>     mark_unsync(p_i);
> 
> Then, mark_unsync() finds the parent sp including that p_i to
> set ->unsync_child_bitmap and increment ->unsync_children if
> necessary.  It may also call kvm_mmu_mark_parents_unsync()
> recursively.

I agree.  sp->parent_ptes goes up one level from sp;
kvm_mmu_mark_parents_unsync(sp) visits the level above sp, while
mark_unsync(sp) visit sp and all the levels above it.

Calling mark_unsync(parent_pte) is enough to complete the visit, after
kvm_mmu_mark_parents_unsync has already processed the level above sp.

Paolo
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