Re: [PATCH 2/6] KVM MMU: fix kvm_mmu_zap_page() and its calling path

Xiao Guangrong
2010-04-14T02:14:29Z

Marcelo Tosatti wrote:
> On Tue, Apr 13, 2010 at 09:34:14AM +0800, Xiao Guangrong wrote:
>>
>> Marcelo Tosatti wrote:
>>
>>>> @@ -1483,8 +1483,8 @@ static int mmu_zap_unsync_children(struct kvm *kvm,
>>>> for_each_sp(pages, sp, parents, i) {
>>>> kvm_mmu_zap_page(kvm, sp);
>>>> mmu_pages_clear_parents(&parents);
>>>> + zapped++;
>>>> }
>>>> - zapped += pages.nr;
>>>> kvm_mmu_pages_init(parent, &parents, &pages);
>>>> }
>>> Don't see why this is needed? The for_each_sp loop uses pvec.nr.
>> I think mmu_zap_unsync_children() should return the number of zapped pages then we
>> can adjust the number of free pages in kvm_mmu_change_mmu_pages(), but pages.nr no
>> only includes the unsync/zapped pages but also includes their parents.
>
> Oh i see. I think its safer to check for list_empty then to rely on
> proper accounting there, like __kvm_mmu_free_some_pages does.

Do you mean that we'd better add WARN_ON(list_empty()) code in kvm_mmu_zap_page()?

Thanks,
Xiao