From: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
To: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Avi Kivity <avi@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>
Subject: Re: [PATCH] mm: mmu_notifier: fix inconsistent memory between secondary MMU and host
Date: Wed, 22 Aug 2012 13:37:59 +0800 [thread overview]
Message-ID: <50347037.3040209@linux.vnet.ibm.com> (raw)
In-Reply-To: <alpine.LSU.2.00.1208212105370.3415@eggly.anvils>
On 08/22/2012 12:12 PM, Hugh Dickins wrote:
> On Wed, 22 Aug 2012, Xiao Guangrong wrote:
>> On 08/21/2012 11:06 PM, Andrea Arcangeli wrote:
>>>
>>> The KSM usage of it looks safe because it will only establish readonly
>>> ptes with it.
>>
>> Hmm, in KSM code, i found this code in replace_page:
>>
>> set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));
>>
>> It is possible to establish a writable pte, no?
>
> No: we only do KSM in private vmas (!VM_SHARED), and because of the
> need to CopyOnWrite in those, vm_page_prot excludes write permission:
> write permission has to be added on COW fault.
After read the code carefully, yes, you are right. Thank you very much
for your explanation, Hugh! :)
WARNING: multiple messages have this Message-ID (diff)
From: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
To: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Avi Kivity <avi@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>
Subject: Re: [PATCH] mm: mmu_notifier: fix inconsistent memory between secondary MMU and host
Date: Wed, 22 Aug 2012 13:37:59 +0800 [thread overview]
Message-ID: <50347037.3040209@linux.vnet.ibm.com> (raw)
In-Reply-To: <alpine.LSU.2.00.1208212105370.3415@eggly.anvils>
On 08/22/2012 12:12 PM, Hugh Dickins wrote:
> On Wed, 22 Aug 2012, Xiao Guangrong wrote:
>> On 08/21/2012 11:06 PM, Andrea Arcangeli wrote:
>>>
>>> The KSM usage of it looks safe because it will only establish readonly
>>> ptes with it.
>>
>> Hmm, in KSM code, i found this code in replace_page:
>>
>> set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));
>>
>> It is possible to establish a writable pte, no?
>
> No: we only do KSM in private vmas (!VM_SHARED), and because of the
> need to CopyOnWrite in those, vm_page_prot excludes write permission:
> write permission has to be added on COW fault.
After read the code carefully, yes, you are right. Thank you very much
for your explanation, Hugh! :)
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next prev parent reply other threads:[~2012-08-22 5:38 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-21 9:46 [PATCH] mm: mmu_notifier: fix inconsistent memory between secondary MMU and host Xiao Guangrong
2012-08-21 9:46 ` Xiao Guangrong
2012-08-21 15:06 ` Andrea Arcangeli
2012-08-21 15:06 ` Andrea Arcangeli
2012-08-21 15:06 ` Andrea Arcangeli
2012-08-22 3:51 ` Xiao Guangrong
2012-08-22 3:51 ` Xiao Guangrong
2012-08-22 4:12 ` Hugh Dickins
2012-08-22 4:12 ` Hugh Dickins
2012-08-22 5:37 ` Xiao Guangrong [this message]
2012-08-22 5:37 ` Xiao Guangrong
2012-08-22 16:37 ` Andrea Arcangeli
2012-08-22 16:37 ` Andrea Arcangeli
2012-08-23 7:25 ` Xiao Guangrong
2012-08-23 7:25 ` Xiao Guangrong
2012-08-22 6:03 ` Xiao Guangrong
2012-08-22 6:03 ` Xiao Guangrong
2012-08-22 16:29 ` Andrea Arcangeli
2012-08-22 16:29 ` Andrea Arcangeli
2012-08-22 19:15 ` Andrew Morton
2012-08-22 19:15 ` Andrew Morton
2012-08-22 19:50 ` Andrea Arcangeli
2012-08-22 19:50 ` Andrea Arcangeli
2012-08-22 19:58 ` Andrew Morton
2012-08-22 19:58 ` Andrew Morton
2012-08-22 20:14 ` Andrea Arcangeli
2012-08-22 20:14 ` Andrea Arcangeli
2012-08-23 7:34 ` Xiao Guangrong
2012-08-23 7:34 ` Xiao Guangrong
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