linux-kernel - Re: [PATCH 2/5] KVM: MMU: split the operations of kvm_mmu_zap

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Date:	Sun, 30 May 2010 16:16:51 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>
Subject: Re: [PATCH 2/5] KVM: MMU: split the operations of kvm_mmu_zap_page()

On 05/30/2010 03:37 PM, Xiao Guangrong wrote:
> Using kvm_mmu_prepare_zap_page() and kvm_mmu_commit_zap_page() to
> split kvm_mmu_zap_page() function, then we can:
>
> - traverse hlist safely
> - easily to gather remote tlb flush which occurs during page zapped
>
>
> +static int kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp)
> +{
> +	int ret;
> +
> +	trace_kvm_mmu_zap_page(sp);
> +	++kvm->stat.mmu_shadow_zapped;
> +	ret = mmu_zap_unsync_children(kvm, sp);
> +	kvm_mmu_page_unlink_children(kvm, sp);
> +	kvm_mmu_unlink_parents(kvm, sp);
> +	if (!sp->role.invalid&&  !sp->role.direct)
> +		unaccount_shadowed(kvm, sp->gfn);
> +	if (sp->unsync)
> +		kvm_unlink_unsync_page(kvm, sp);
> +	if (!sp->root_count)
> +		/* Count self */
> +		ret++;
> +	else
> +		kvm_reload_remote_mmus(kvm);
> +
> +	sp->role.invalid = 1;
> +	list_move(&sp->link,&kvm->arch.invalid_mmu_pages);
> +	kvm_mmu_reset_last_pte_updated(kvm);
> +	return ret;
> +}
> +
> +static void kvm_mmu_commit_zap_page(struct kvm *kvm)
> +{
> +	struct kvm_mmu_page *sp, *n;
> +
> +	if (list_empty(&kvm->arch.invalid_mmu_pages))
> +		return;
> +
> +	kvm_flush_remote_tlbs(kvm);
> +	list_for_each_entry_safe(sp, n,&kvm->arch.invalid_mmu_pages, link) {
> +		WARN_ON(!sp->role.invalid);
> +		if (!sp->root_count)
> +			kvm_mmu_free_page(kvm, sp);
> +	}
> +}
> +
>    

You're adding two new functions but not using them here?  Possibly in 
the old kvm_mmu_zap_page()?

> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 5e5cd8d..225c3c4 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5331,6 +5331,7 @@ struct  kvm *kvm_arch_create_vm(void)
>   	}
>
>   	INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
> +	INIT_LIST_HEAD(&kvm->arch.invalid_mmu_pages);
>   	INIT_LIST_HEAD(&kvm->arch.assigned_dev_head);
>    

This is a good idea, but belongs in a separate patch?  We can use it to 
reclaim invalid pages before allocating new ones.

-- 
error compiling committee.c: too many arguments to function

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