From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751676AbcGGMaQ (ORCPT ); Thu, 7 Jul 2016 08:30:16 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:35962 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751087AbcGGMaJ (ORCPT ); Thu, 7 Jul 2016 08:30:09 -0400 Subject: Re: [PATCH v4 1/2] KVM: nVMX: Fix incorrect preemption timer vmexit in nested guest To: Wanpeng Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <1467893939-3335-1-git-send-email-wanpeng.li@hotmail.com> Cc: Wanpeng Li , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Yunhong Jiang , Jan Kiszka , Haozhong Zhang From: Paolo Bonzini Message-ID: <5c9f55f7-37c6-ef12-0dc2-7b630fa16f69@redhat.com> Date: Thu, 7 Jul 2016 14:29:45 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 MIME-Version: 1.0 In-Reply-To: <1467893939-3335-1-git-send-email-wanpeng.li@hotmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/07/2016 14:18, Wanpeng Li wrote: > From: Wanpeng Li > > BUG: unable to handle kernel NULL pointer dereference at (null) > IP: [< (null)>] (null) > PGD 0 > Oops: 0010 [#1] SMP > Call Trace: > ? kvm_lapic_expired_hv_timer+0x47/0x90 [kvm] > handle_preemption_timer+0xe/0x20 [kvm_intel] > vmx_handle_exit+0x169/0x15a0 [kvm_intel] > ? kvm_arch_vcpu_ioctl_run+0xd5d/0x19d0 [kvm] > kvm_arch_vcpu_ioctl_run+0xdee/0x19d0 [kvm] > ? kvm_arch_vcpu_ioctl_run+0xd5d/0x19d0 [kvm] > ? vcpu_load+0x1c/0x60 [kvm] > ? kvm_arch_vcpu_load+0x57/0x260 [kvm] > kvm_vcpu_ioctl+0x2d3/0x7c0 [kvm] > do_vfs_ioctl+0x96/0x6a0 > ? __fget_light+0x2a/0x90 > SyS_ioctl+0x79/0x90 > do_syscall_64+0x68/0x180 > entry_SYSCALL64_slow_path+0x25/0x25 > Code: Bad RIP value. > RIP [< (null)>] (null) > RSP > CR2: 0000000000000000 > ---[ end trace 9c70c48b1a2bc66e ]--- > > This can be reproduced readily by preemption timer enabled on L0 and disabled > on L1. > > Preemption timer for nested VMX is emulated by hrtimer which is started on L2 > entry, stopped on L2 exit and evaluated via the check_nested_events hook. However, > nested_vmx_exit_handled is always return true for preemption timer vmexit, then > the L1 preemption timer vmexit is captured and be treated as a L2 preemption > timer vmexit, incurr a nested vmexit dereference NULL pointer. > > This patch fix it by depending on check_nested_events to capture L2 preemption > timer(emulated hrtimer) expire and nested vmexit. > > Tested-by: Haozhong Zhang > Cc: Paolo Bonzini > Cc: Radim Krčmář > Cc: Yunhong Jiang > Cc: Jan Kiszka > Cc: Haozhong Zhang > Signed-off-by: Wanpeng Li > --- > v2 -> v3: > * update patch subject > v1 -> v2: > * fix typo in patch description > > arch/x86/kvm/vmx.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index 85e2f0a..29c16a8 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -8041,6 +8041,8 @@ static bool nested_vmx_exit_handled(struct kvm_vcpu *vcpu) > return nested_cpu_has2(vmcs12, SECONDARY_EXEC_XSAVES); > case EXIT_REASON_PCOMMIT: > return nested_cpu_has2(vmcs12, SECONDARY_EXEC_PCOMMIT); > + case EXIT_REASON_PREEMPTION_TIMER: > + return false; > default: > return true; > } > Thanks, applied to kvm/queue. Paolo