From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx148.postini.com [74.125.245.148]) by kanga.kvack.org (Postfix) with SMTP id 22D876B0044 for ; Wed, 22 Aug 2012 00:12:57 -0400 (EDT) Received: by iahk25 with SMTP id k25so522605iah.14 for ; Tue, 21 Aug 2012 21:12:56 -0700 (PDT) Date: Tue, 21 Aug 2012 21:12:09 -0700 (PDT) From: Hugh Dickins Subject: Re: [PATCH] mm: mmu_notifier: fix inconsistent memory between secondary MMU and host In-Reply-To: <50345735.2000807@linux.vnet.ibm.com> Message-ID: References: <503358FF.3030009@linux.vnet.ibm.com> <20120821150618.GJ27696@redhat.com> <50345735.2000807@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Xiao Guangrong Cc: Andrea Arcangeli , Andrew Morton , Avi Kivity , Marcelo Tosatti , LKML , KVM , Linux Memory Management List 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. Hugh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org