From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753420AbdHWHNw (ORCPT ); Wed, 23 Aug 2017 03:13:52 -0400 Received: from mail-wm0-f65.google.com ([74.125.82.65]:33164 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753318AbdHWHNu (ORCPT ); Wed, 23 Aug 2017 03:13:50 -0400 Subject: Re: [PATCH v3] KVM: nVMX: Fix trying to cancel vmlauch/vmresume To: Wanpeng Li Cc: "linux-kernel@vger.kernel.org" , kvm , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Wanpeng Li References: <1503356912-117219-1-git-send-email-wanpeng.li@hotmail.com> <0467288d-1e3d-0ea0-dd8a-c034dcac6ee1@redhat.com> From: Paolo Bonzini Message-ID: Date: Wed, 23 Aug 2017 09:13:47 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22/08/2017 23:57, Wanpeng Li wrote: > 2017-08-23 0:09 GMT+08:00 Paolo Bonzini : >> On 22/08/2017 01:08, Wanpeng Li wrote: >>> From: Wanpeng Li >>> >>> ------------[ cut here ]------------ >>> WARNING: CPU: 7 PID: 3861 at /home/kernel/ssd/kvm/arch/x86/kvm//vmx.c:11299 nested_vmx_vmexit+0x176e/0x1980 [kvm_intel] >>> CPU: 7 PID: 3861 Comm: qemu-system-x86 Tainted: G W OE 4.13.0-rc4+ #11 >>> RIP: 0010:nested_vmx_vmexit+0x176e/0x1980 [kvm_intel] >>> Call Trace: >>> ? kvm_multiple_exception+0x149/0x170 [kvm] >>> ? handle_emulation_failure+0x79/0x230 [kvm] >>> ? load_vmcs12_host_state+0xa80/0xa80 [kvm_intel] >>> ? check_chain_key+0x137/0x1e0 >>> ? reexecute_instruction.part.168+0x130/0x130 [kvm] >>> nested_vmx_inject_exception_vmexit+0xb7/0x100 [kvm_intel] >>> ? nested_vmx_inject_exception_vmexit+0xb7/0x100 [kvm_intel] >>> vmx_queue_exception+0x197/0x300 [kvm_intel] >>> kvm_arch_vcpu_ioctl_run+0x1b0c/0x2c90 [kvm] >>> ? kvm_arch_vcpu_runnable+0x220/0x220 [kvm] >>> ? preempt_count_sub+0x18/0xc0 >>> ? restart_apic_timer+0x17d/0x300 [kvm] >>> ? kvm_lapic_restart_hv_timer+0x37/0x50 [kvm] >>> ? kvm_arch_vcpu_load+0x1d8/0x350 [kvm] >>> kvm_vcpu_ioctl+0x4e4/0x910 [kvm] >>> ? kvm_vcpu_ioctl+0x4e4/0x910 [kvm] >>> ? kvm_dev_ioctl+0xbe0/0xbe0 [kvm] >>> >>> The flag "nested_run_pending", which can override the decision of which should run >>> next, L1 or L2. nested_run_pending=1 means that we *must* run L2 next, not L1. This >>> is necessary in particular when L1 did a VMLAUNCH of L2 and therefore expects L2 to >>> be run (and perhaps be injected with an event it specified, etc.). Nested_run_pending >>> is especially intended to avoid switching to L1 in the injection decision-point. >>> >>> I catch this in the queue exception path, this patch fixes it by running L2 next >>> instead of L1 in the queue exception path and injecting the pending exception to >>> L2 directly. >>> >>> Cc: Paolo Bonzini >>> Cc: Radim Krčmář >>> Signed-off-by: Wanpeng Li >>> --- >>> v2 -> v3: >>> * move the nested_run_pending to the else branch >>> v1 -> v2: >>> * request an immediate VM exit from L2 and keep the exception for >>> L1 pending for a subsequent nested VM exit >>> >>> arch/x86/kvm/vmx.c | 4 ++++ >>> 1 file changed, 4 insertions(+) >>> >>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >>> index e398946..685f51e 100644 >>> --- a/arch/x86/kvm/vmx.c >>> +++ b/arch/x86/kvm/vmx.c >>> @@ -2488,6 +2488,10 @@ static int nested_vmx_check_exception(struct kvm_vcpu *vcpu) >>> } >>> } else { >>> unsigned long exit_qual = 0; >>> + >>> + if (to_vmx(vcpu)->nested.nested_run_pending) >>> + return 0; >>> + >>> if (nr == DB_VECTOR) >>> exit_qual = vcpu->arch.dr6; >>> >>> >> >> Hmm, why would this not apply to page faults? It doesn't make much sense... > > Agreed, I do this in v1, please have a look. On the other hand Radim was right in his review of v1 (and sort of wrong in the review of v2). I replied there. Paolo