From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v3 01/11] KVM: MMU: avoid pte_list_desc running out in kvm_mmu_pte_write Date: Tue, 13 Sep 2011 12:51:12 +0300 Message-ID: <4E6F2790.4020602@redhat.com> References: <4E5C4C20.3000403@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , KVM To: Xiao Guangrong Return-path: In-Reply-To: <4E5C4C20.3000403@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 08/30/2011 05:34 AM, Xiao Guangrong wrote: > kvm_mmu_pte_write is unsafe since we need to alloc pte_list_desc in the > function when spte is prefetched, unfortunately, we can not know how many > spte need to be prefetched on this path, that means we can use out of the > free pte_list_desc object in the cache, and BUG_ON() is triggered, also some > path does not fill the cache, such as INS instruction emulated that does not > trigger page fault > > @@ -3716,10 +3735,6 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code, > goto out; > } > > - r = mmu_topup_memory_caches(vcpu); > - if (r) > - goto out; > - > er = x86_emulate_instruction(vcpu, cr2, 0, insn, insn_len); > Suppose we are out of memory, can't this get us in an endless loop? return -ENOMEM breaks as out (and kills the guest, likely). -- error compiling committee.c: too many arguments to function