Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752281AbdGSFe0 (ORCPT ); Wed, 19 Jul 2017 01:34:26 -0400 Received: from mail-oi0-f68.google.com ([209.85.218.68]:35493 "EHLO mail-oi0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751364AbdGSFeY (ORCPT ); Wed, 19 Jul 2017 01:34:24 -0400 MIME-Version: 1.0 In-Reply-To: <1499757180-20439-1-git-send-email-wanpeng.li@hotmail.com> References: <1499757180-20439-1-git-send-email-wanpeng.li@hotmail.com> From: Wanpeng Li Date: Wed, 19 Jul 2017 13:34:23 +0800 Message-ID: Subject: Re: [PATCH] KVM: VMX: Fix invalid guest state detection after task-switch emulation To: "linux-kernel@vger.kernel.org" , kvm Cc: Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Wanpeng Li , Nadav Amit 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 v6J5YUMK030515 Content-Length: 1826 Lines: 50 Ping, :) 2017-07-11 15:13 GMT+08:00 Wanpeng Li : > From: Wanpeng Li > > This can be reproduced by EPT=1, unrestricted_guest=N, emulate_invalid_state=Y > or EPT=0, the trace of kvm-unit-tests/taskswitch2.flat is like below, it tries > to emulate invalid guest state task-switch: > > kvm_exit: reason TASK_SWITCH rip 0x0 info 40000058 0 > kvm_emulate_insn: 42000:0:0f 0b (0x2) > kvm_emulate_insn: 42000:0:0f 0b (0x2) failed > kvm_inj_exception: #UD (0x0) > kvm_entry: vcpu 0 > kvm_exit: reason TASK_SWITCH rip 0x0 info 40000058 0 > kvm_emulate_insn: 42000:0:0f 0b (0x2) > kvm_emulate_insn: 42000:0:0f 0b (0x2) failed > kvm_inj_exception: #UD (0x0) > ...................... > > It appears that the task-switch emulation updates rflags (and vm86 > flag) only after the segments are loaded, causing vmx->emulation_required > to be set, when in fact invalid guest state emulation is not needed. > > This patch fixes it by updating vmx->emulation_required after the > rflags (and vm86 flag) is updated in task-switch emulation. > > Suggested-by: Nadav Amit > Cc: Paolo Bonzini > Cc: Radim Krčmář > Cc: Nadav Amit > Signed-off-by: Wanpeng Li > --- > arch/x86/kvm/vmx.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index f50cbfd..70270a2 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -6255,6 +6255,7 @@ static int handle_task_switch(struct kvm_vcpu *vcpu) > * TODO: What about debug traps on tss switch? > * Are we supposed to inject them and update dr6? > */ > + vmx->emulation_required = emulation_required(vcpu); > > return 1; > } > -- > 2.7.4 >