From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v5 2/9] KVM: MMU: fix race between 'walk_addr' and 'fetch' Date: Sun, 11 Jul 2010 18:40:07 +0300 Message-ID: <4C39E5D7.7030703@redhat.com> References: <4C330918.6040709@cn.fujitsu.com> <4C330948.1070305@cn.fujitsu.com> <4C39BE90.1030802@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , KVM list To: Xiao Guangrong Return-path: In-Reply-To: <4C39BE90.1030802@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 07/11/2010 03:52 PM, Avi Kivity wrote: > On 07/06/2010 01:45 PM, Xiao Guangrong wrote: >> 'walk_addr' is out of mmu_lock's protection, so while we handle 'fetch', >> then guest's mapping has modifited by other vcpu's write path, such as >> invlpg, pte_write and other fetch path >> >> Fixed by checking all level's mapping >> >> >> @@ -319,22 +319,23 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, >> gva_t addr, >> direct_access&= ~ACC_WRITE_MASK; >> >> for_each_shadow_entry(vcpu, addr, iterator) { >> + bool nonpresent = false, last_mapping = false; >> + > > I don't like these two new variables, but no suggestion at the > moment. I'll try to simplify this loop later. > > One idea may be: > > while (level > walker.level) { > handle indirect pages > } > while (level > hlevel) { > handle direct pages > } > handle last spte > > I'm worried that this change is too big for backporting, but no > suggestions on how to make it smaller, so we'll have to accept it. Okay, I couldn't resist, posting this soon. -- error compiling committee.c: too many arguments to function