From mboxrd@z Thu Jan  1 00:00:00 1970
From: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Subject: Re: [PATCH v2] KVM: Avoid zapping unrelated shadows in __kvm_set_memory_region()
Date: Wed, 11 Apr 2012 11:11:07 +0800
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Cc: avi@redhat.com, mtosatti@redhat.com, kvm@vger.kernel.org,
	yoshikawa.takuya@oss.ntt.co.jp
To: Takuya Yoshikawa <takuya.yoshikawa@gmail.com>
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On 04/10/2012 09:05 PM, Takuya Yoshikawa wrote:

 
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 29ad6f9..a50f7ba 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -3930,16 +3930,30 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
>  	kvm_flush_remote_tlbs(kvm);
>  }
> 
> -void kvm_mmu_zap_all(struct kvm *kvm)
> +/**
> + * kvm_mmu_zap_all - zap all shadows which have mappings into a given slot
> + * @kvm: the kvm instance
> + * @slot: id of the target slot
> + *
> + * If @slot is -1, zap all shadow pages.
> + */
> +void kvm_mmu_zap_all(struct kvm *kvm, int slot)
>  {
>  	struct kvm_mmu_page *sp, *node;
>  	LIST_HEAD(invalid_list);
> +	int zapped;
> 
>  	spin_lock(&kvm->mmu_lock);
>  restart:
> -	list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link)
> -		if (kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list))
> -			goto restart;
> +	zapped = 0;
> +	list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) {
> +		if ((slot >= 0) && !test_bit(slot, sp->slot_bitmap))
> +			continue;
> +
> +		zapped |= kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);


You should "goto restart" here like the origin code, also, "safe" version of
list_for_each is not needed.