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From: Xiao Guangrong <xiaoguangrong.eric@gmail.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>,
	Avi Kivity <avi@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
	KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH v3 4/9] KVM: MMU: introduce SPTE_ALLOW_WRITE bit
Date: Sat, 21 Apr 2012 11:30:55 +0800	[thread overview]
Message-ID: <4F9229EF.4010506@gmail.com> (raw)
In-Reply-To: <20120420213925.GB13817@amt.cnet>

On 04/21/2012 05:39 AM, Marcelo Tosatti wrote:


>> @@ -1177,9 +1178,8 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned long *rmapp,
>>  			new_spte = *sptep & ~PT64_BASE_ADDR_MASK;
>>  			new_spte |= (u64)new_pfn << PAGE_SHIFT;
>>
>> -			new_spte &= ~PT_WRITABLE_MASK;
>> -			new_spte &= ~SPTE_HOST_WRITEABLE;
>> -			new_spte &= ~shadow_accessed_mask;
>> +			new_spte &= ~(PT_WRITABLE_MASK | SPTE_HOST_WRITEABLE |
>> +				      shadow_accessed_mask | SPTE_ALLOW_WRITE);
> 
> Each bit should have a distinct meaning. Here the host pte is being
> write-protected, which means only the SPTE_HOST_WRITEABLE bit
> should be cleared.


Hmm, it is no problem if SPTE_ALLOW_WRITE is not cleared.

But the meaning of SPTE_ALLOW_WRITE will become strange: we will see a
spte with spte.SPTE_ALLOW_WRITE = 1 (means the spte is writable on host
and guest) and spte.SPTE_HOST_WRITEABLE = 0 (means the spte is read-only
on host).


  reply	other threads:[~2012-04-21  3:31 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-20  8:16 [PATCH v3 0/9] KVM: MMU: fast page fault Xiao Guangrong
2012-04-20  8:17 ` [PATCH v3 1/9] KVM: MMU: return bool in __rmap_write_protect Xiao Guangrong
2012-04-20  8:17 ` [PATCH v3 2/9] KVM: MMU: abstract spte write-protect Xiao Guangrong
2012-04-20 21:33   ` Marcelo Tosatti
2012-04-21  1:10     ` Takuya Yoshikawa
2012-04-21  4:34       ` Xiao Guangrong
2012-04-21  3:24     ` Xiao Guangrong
2012-04-21  4:18       ` Marcelo Tosatti
2012-04-21  6:52         ` Xiao Guangrong
2012-04-20  8:18 ` [PATCH v3 3/9] KVM: VMX: export PFEC.P bit on ept Xiao Guangrong
2012-04-20  8:18 ` [PATCH v3 4/9] KVM: MMU: introduce SPTE_ALLOW_WRITE bit Xiao Guangrong
2012-04-20 21:39   ` Marcelo Tosatti
2012-04-21  3:30     ` Xiao Guangrong [this message]
2012-04-21  4:22       ` Marcelo Tosatti
2012-04-21  6:55         ` Xiao Guangrong
2012-04-22 15:12         ` Avi Kivity
2012-04-23  7:24           ` Xiao Guangrong
2012-04-20  8:19 ` [PATCH v3 5/9] KVM: MMU: introduce SPTE_WRITE_PROTECT bit Xiao Guangrong
2012-04-20 21:52   ` Marcelo Tosatti
2012-04-21  0:40     ` Marcelo Tosatti
2012-04-21  0:55       ` Marcelo Tosatti
2012-04-21  1:38         ` Takuya Yoshikawa
2012-04-21  4:29         ` Xiao Guangrong
2012-04-21  4:00       ` Xiao Guangrong
2012-04-24  0:45         ` Marcelo Tosatti
2012-04-24  3:34           ` Xiao Guangrong
2012-04-21  3:47     ` Xiao Guangrong
2012-04-21  4:38       ` Marcelo Tosatti
2012-04-21  7:25         ` Xiao Guangrong
2012-04-24  0:24           ` Marcelo Tosatti
2012-04-20  8:19 ` [PATCH v3 6/9] KVM: MMU: fast path of handling guest page fault Xiao Guangrong
2012-04-20  8:20 ` [PATCH v3 7/9] KVM: MMU: trace fast " Xiao Guangrong
2012-04-20  8:20 ` [PATCH v3 8/9] KVM: MMU: fix kvm_mmu_pagetable_walk tracepoint Xiao Guangrong
2012-04-20  8:21 ` [PATCH v3 9/9] KVM: MMU: document mmu-lock and fast page fault Xiao Guangrong
2012-04-21  0:59 ` [PATCH v3 0/9] KVM: MMU: " Marcelo Tosatti

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