Re: [PATCH 1/3] KVM MMU: make kvm_mmu_zap_page() return the number of zapped sp in total.

[Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>]

Gui Jianfeng wrote:
> Currently, in kvm_mmu_change_mmu_pages(kvm, page), "used_pages--" is  performed after calling
> kvm_mmu_zap_page() in spite of that whether "page" is actually reclaimed. Because root sp won't be 
> reclaimed by kvm_mmu_zap_page(). So making kvm_mmu_zap_page() return total number of reclaimed sp
> makes more sense. A new flag is put into kvm_mmu_zap_page() to indicate whether the top page is reclaimed.
> 

This bug only hurts kvm_mmu_change_mmu_pages() function, we'd better allow 'self_deleted' is
NULL, then we can pass NULL at other place.

> @@ -1571,7 +1584,8 @@ restart:
>  			pgprintk("%s: gfn %lx role %x\n", __func__, gfn,
>  				 sp->role.word);
>  			r = 1;
> -			if (kvm_mmu_zap_page(kvm, sp))
> +			ret = kvm_mmu_zap_page(kvm, sp, &self_deleted);
> +			if (ret > 1 || (ret == 1 && self_deleted == 0))
>  				goto restart;

Maybe we can keep kvm_mmu_zap_page() returns the number of zapped children,
and 'self_deleted' indicates whether self is zapped, then we no need modify
those function, just fix kvm_mmu_change_mmu_pages() that is if 'self_deleted == 1',
inc 'used_pages'

Xiao