linux-kernel - Re: [PATCH v7 02/10] KVM: MMU: abstract spte write-protect

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Message-Id: <20120620180254.8b3a42f8.yoshikawa.takuya@oss.ntt.co.jp>
Date:	Wed, 20 Jun 2012 18:02:54 +0900
From:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v7 02/10] KVM: MMU: abstract spte write-protect

On Wed, 20 Jun 2012 15:57:15 +0800
Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com> wrote:

> Introduce a common function to abstract spte write-protect to
> cleanup the code
> 
> Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>

...

> +/* Return true if the spte is dropped. */
> +static bool spte_write_protect(struct kvm *kvm, u64 *sptep, bool *flush)
> +{
> +	u64 spte = *sptep;
> +
> +	if (!is_writable_pte(spte))
> +		return false;
> +
> +	rmap_printk("rmap_write_protect: spte %p %llx\n", sptep, *sptep);

...

> @@ -3902,16 +3915,7 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
>  			      !is_last_spte(pt[i], sp->role.level))
>  				continue;
> 
> -			if (is_large_pte(pt[i])) {
> -				drop_spte(kvm, &pt[i]);
> -				--kvm->stat.lpages;
> -				continue;
> -			}
> -
> -			/* avoid RMW */
> -			if (is_writable_pte(pt[i]))
> -				mmu_spte_update(&pt[i],
> -						pt[i] & ~PT_WRITABLE_MASK);
> +			spte_write_protect(kvm, &pt[i], &flush);

Adding rmap_printk() here seems wrong.

If you think it is not a problem, please explain why you think so in
the changelog.

Thanks,
	Takuya
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