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From: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
To: Takuya Yoshikawa <takuya.yoshikawa@gmail.com>
Cc: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>,
	Avi Kivity <avi@redhat.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH v7 02/10] KVM: MMU: abstract spte write-protect
Date: Wed, 20 Jun 2012 21:21:07 +0800	[thread overview]
Message-ID: <4FE1CE43.9080203@linux.vnet.ibm.com> (raw)
In-Reply-To: <20120620215653.15930f3467bc13748d548b0d@gmail.com>

On 06/20/2012 08:56 PM, Takuya Yoshikawa wrote:

> On Wed, 20 Jun 2012 17:11:06 +0800
> Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> wrote:
> 
>> Strange! Why do you think it is wrong? It is just debug code.
> 
> kvm_mmu_slot_remove_write_access() does not use rmap but the debug code says:
> 	rmap_printk("rmap_write_protect: spte %p %llx\n", sptep, *sptep);


It is not a problem since all sptes which are pointing to gfn is existed in rmap.

> 
>>> If you think it is not a problem, please explain why you think so in
>>> the changelog.
>>
>>
>> It is a from the first place and it is used to debug and not compiled at all.
> 
> It was not in kvm_mmu_slot_remove_write_access() before, no?
> 
> This patch says that the write protection code becomes commonly usable
> function, but it still has rmap_write_protect specific debug code in it;
> using it in kvm_mmu_slot_remove_write_access(), which is not at all related
> to rmap_write_protect, is strange.
> 
> As you say, this is just debug code and does not have any practical problem.
> But randomly putting debug code is not a good thing.
> 


Again, "rmap" does not break the logic, the spte we handle in this function must
be in rmap.


  reply	other threads:[~2012-06-20 13:21 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-06-20  7:56 [PATCH v7 00/10] KVM: MMU: fast page fault Xiao Guangrong
2012-06-20  7:56 ` [PATCH v7 01/10] KVM: MMU: return bool in __rmap_write_protect Xiao Guangrong
2012-06-20  7:57 ` [PATCH v7 02/10] KVM: MMU: abstract spte write-protect Xiao Guangrong
2012-06-20  9:02   ` Takuya Yoshikawa
2012-06-20  9:11     ` Xiao Guangrong
2012-06-20 12:56       ` Takuya Yoshikawa
2012-06-20 13:21         ` Xiao Guangrong [this message]
2012-06-20 14:11           ` Takuya Yoshikawa
2012-06-21  1:48             ` Xiao Guangrong
2012-06-21  1:56               ` Takuya Yoshikawa
2012-07-11 13:32               ` Avi Kivity
2012-06-20  7:57 ` [PATCH v7 03/10] KVM: MMU: cleanup spte_write_protect Xiao Guangrong
2012-06-20  7:58 ` [PATCH v7 04/10] KVM: VMX: export PFEC.P bit on ept Xiao Guangrong
2012-06-20  7:58 ` [PATCH v7 05/10] KVM: MMU: fold tlb flush judgement into mmu_spte_update Xiao Guangrong
2012-06-20  7:58 ` [PATCH v7 06/10] KVM: MMU: introduce SPTE_MMU_WRITEABLE bit Xiao Guangrong
2012-06-20  7:59 ` [PATCH v7 07/10] KVM: MMU: fast path of handling guest page fault Xiao Guangrong
2012-06-20  7:59 ` [PATCH v7 08/10] KVM: MMU: trace fast " Xiao Guangrong
2012-06-20  8:00 ` [PATCH v7 09/10] KVM: MMU: fix kvm_mmu_pagetable_walk tracepoint Xiao Guangrong
2012-06-20  8:00 ` [PATCH v7 10/10] KVM: MMU: document mmu-lock and fast page fault Xiao Guangrong
2012-07-03 15:11 ` [PATCH v7 00/10] KVM: MMU: " Marcelo Tosatti
2012-07-11 13:51 ` Avi Kivity

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