From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751698AbdINL6X (ORCPT ); Thu, 14 Sep 2017 07:58:23 -0400 Received: from mail-io0-f194.google.com ([209.85.223.194]:35144 "EHLO mail-io0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751618AbdINL6W (ORCPT ); Thu, 14 Sep 2017 07:58:22 -0400 X-Google-Smtp-Source: AOwi7QD3JvHtwCAouRIffLIDeEbICyyP+YtpRCa3tVNn+5gVQwsivDthQzTObJhbtoboyqI8nCY6rl2PJZDh2CxoUUw= MIME-Version: 1.0 In-Reply-To: References: <1505300602-7236-1-git-send-email-wanpeng.li@hotmail.com> From: Wanpeng Li Date: Thu, 14 Sep 2017 19:58:20 +0800 Message-ID: Subject: Re: [PATCH 1/2] KVM: nVMX: Fix nested #PF intends to break L1's vmlauch/vmresume To: Paolo Bonzini Cc: "linux-kernel@vger.kernel.org" , kvm , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Wanpeng Li Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id v8EBwTmH029623 2017-09-14 7:14 GMT+08:00 Wanpeng Li : > 2017-09-14 5:45 GMT+08:00 Paolo Bonzini : >> On 13/09/2017 13:03, Wanpeng Li wrote: >>> From: Wanpeng Li >>> >>> ------------[ cut here ]------------ >>> WARNING: CPU: 4 PID: 5280 at /home/kernel/linux/arch/x86/kvm//vmx.c:11394 nested_vmx_vmexit+0xc2b/0xd70 [kvm_intel] >>> CPU: 4 PID: 5280 Comm: qemu-system-x86 Tainted: G W OE 4.13.0+ #17 >>> RIP: 0010:nested_vmx_vmexit+0xc2b/0xd70 [kvm_intel] >>> Call Trace: >>> ? emulator_read_emulated+0x15/0x20 [kvm] >>> ? segmented_read+0xae/0xf0 [kvm] >>> vmx_inject_page_fault_nested+0x60/0x70 [kvm_intel] >>> ? vmx_inject_page_fault_nested+0x60/0x70 [kvm_intel] >>> x86_emulate_instruction+0x733/0x810 [kvm] >>> vmx_handle_exit+0x2f4/0xda0 [kvm_intel] >>> ? kvm_arch_vcpu_ioctl_run+0xd2f/0x1c60 [kvm] >>> kvm_arch_vcpu_ioctl_run+0xdab/0x1c60 [kvm] >>> ? kvm_arch_vcpu_load+0x62/0x230 [kvm] >>> kvm_vcpu_ioctl+0x340/0x700 [kvm] >>> ? kvm_vcpu_ioctl+0x340/0x700 [kvm] >>> ? __fget+0xfc/0x210 >>> do_vfs_ioctl+0xa4/0x6a0 >>> ? __fget+0x11d/0x210 >>> SyS_ioctl+0x79/0x90 >>> entry_SYSCALL_64_fastpath+0x23/0xc2 >>> >>> A nested #PF is triggered during L0 emulating instruction for L2. However, it >>> doesn't consider we should not break L1's vmlauch/vmresme. This patch fixes >>> it by queuing the #PF exception instead ,requesting an immediate VM exit from >>> L2 and keeping the exception for L1 pending for a subsequent nested VM exit. >>> >>> Cc: Paolo Bonzini >>> Cc: Radim Krčmář >>> Signed-off-by: Wanpeng Li >>> --- >>> arch/x86/kvm/vmx.c | 3 ++- >>> 1 file changed, 2 insertions(+), 1 deletion(-) >>> >>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >>> index 4253ade..fda9dd6 100644 >>> --- a/arch/x86/kvm/vmx.c >>> +++ b/arch/x86/kvm/vmx.c >>> @@ -9829,7 +9829,8 @@ static void vmx_inject_page_fault_nested(struct kvm_vcpu *vcpu, >>> >>> WARN_ON(!is_guest_mode(vcpu)); >>> >>> - if (nested_vmx_is_page_fault_vmexit(vmcs12, fault->error_code)) { >>> + if (nested_vmx_is_page_fault_vmexit(vmcs12, fault->error_code) && >>> + !to_vmx(vcpu)->nested.nested_run_pending) { >>> vmcs12->vm_exit_intr_error_code = fault->error_code; >>> nested_vmx_vmexit(vcpu, EXIT_REASON_EXCEPTION_NMI, >>> PF_VECTOR | INTR_TYPE_HARD_EXCEPTION | >>> >> >> Is vmx_inject_page_fault_nested even needed at all these days? >> >> kvm_inject_page_fault's call to kvm_queue_exception_e should transform >> into an L2->L1 vmexit when vmx_check_nested_events is called. > > I saw L0 reboot/hang after do something like below: Maybe something associated with which commit ef54bcfee (KVM: x86: skip writeback on injection of nested exception) pointed out, IIUC, fault->nested_page_fault will not be changed in vmx_inject_page_fault_nested(), so we always return false in the case of vcpu->arch.nested.mmu.inject_page_fault(), then the issue which the commit try to avoid is encountered. Regards, Wanpeng Li > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index 4253ade..96b4f6f 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -9822,24 +9822,6 @@ static bool > nested_vmx_is_page_fault_vmexit(struct vmcs12 *vmcs12, > return inequality ^ bit; > } > > -static void vmx_inject_page_fault_nested(struct kvm_vcpu *vcpu, > - struct x86_exception *fault) > -{ > - struct vmcs12 *vmcs12 = get_vmcs12(vcpu); > - > - WARN_ON(!is_guest_mode(vcpu)); > - > - if (nested_vmx_is_page_fault_vmexit(vmcs12, fault->error_code)) { > - vmcs12->vm_exit_intr_error_code = fault->error_code; > - nested_vmx_vmexit(vcpu, EXIT_REASON_EXCEPTION_NMI, > - PF_VECTOR | INTR_TYPE_HARD_EXCEPTION | > - INTR_INFO_DELIVER_CODE_MASK | > INTR_INFO_VALID_MASK, > - fault->address); > - } else { > - kvm_inject_page_fault(vcpu, fault); > - } > -} > - > static inline bool nested_vmx_merge_msr_bitmap(struct kvm_vcpu *vcpu, > struct vmcs12 *vmcs12); > > @@ -10654,7 +10636,7 @@ static int prepare_vmcs02(struct kvm_vcpu > *vcpu, struct vmcs12 *vmcs12, > return 1; > > if (!enable_ept) > - vcpu->arch.walk_mmu->inject_page_fault = > vmx_inject_page_fault_nested; > + vcpu->arch.walk_mmu->inject_page_fault = kvm_inject_page_fault; > > /* > > Regards, > Wanpeng Li