From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751551AbdIOL1F (ORCPT ); Fri, 15 Sep 2017 07:27:05 -0400 Received: from mail-wr0-f195.google.com ([209.85.128.195]:34436 "EHLO mail-wr0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751226AbdIOL1E (ORCPT ); Fri, 15 Sep 2017 07:27:04 -0400 X-Google-Smtp-Source: ADKCNb6h88xzpvAiGwtNsiomWdF+vOgXA5fkGJQDCHwHuC22OeNDShZWy3ftGfkKOPbeE6Wr/xhIEg== Subject: Re: [PATCH 1/2] KVM: nVMX: Fix nested #PF intends to break L1's vmlauch/vmresume From: Paolo Bonzini To: Wanpeng Li Cc: "linux-kernel@vger.kernel.org" , kvm , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Wanpeng Li References: <1505300602-7236-1-git-send-email-wanpeng.li@hotmail.com> Message-ID: <4bf68838-ce0a-93ed-a20d-c1e2799d3651@redhat.com> Date: Fri, 15 Sep 2017 13:27:00 +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 15/09/2017 13:26, Paolo Bonzini wrote: > On 15/09/2017 05:48, Wanpeng Li wrote: >> 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. >> >> After more investigation, this will break the original goal of what >> vmx_inject_page_fault_nested() tries to fix. >> http://www.spinics.net/lists/kvm/msg96579.html > > Right! I think I have a generic patch for the same issue that Gleb > solved there. We can fill in the IDT vectoring info early in the > vmexit, so that the L1 vmexit can overwrite the L2 exception easily. https://www.spinics.net/lists/kvm/msg154640.html Paolo