Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755274AbdGSQT5 (ORCPT ); Wed, 19 Jul 2017 12:19:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56416 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753253AbdGSQT4 (ORCPT ); Wed, 19 Jul 2017 12:19:56 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com E6A0461D19 Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=rkrcmar@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com E6A0461D19 Date: Wed, 19 Jul 2017 18:19:52 +0200 From: Radim =?utf-8?B?S3LEjW3DocWZ?= To: Nadav Amit Cc: Wanpeng Li , "linux-kernel@vger.kernel.org" , kvm , Paolo Bonzini , Wanpeng Li Subject: [PATCH v2] KVM: VMX: Fix invalid guest state detection after task-switch emulation Message-ID: <20170719161952.GC17303@potion> References: <1499757180-20439-1-git-send-email-wanpeng.li@hotmail.com> <20170719112926.GA13502@potion> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Wed, 19 Jul 2017 16:19:56 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3254 Lines: 95 2017-07-19 08:14-0700, Nadav Amit: > Radim Krčmář wrote: > > @@ -2363,6 +2368,8 @@ static unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu) > > > > static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) > > { > > + unsigned long old_rflags = to_vmx(vcpu)->rflags; > > It assumes rflags was decached from the VMCS before. Probably it is true, but… Right, it's better to use accessors everywhere, thanks. The line should read: + unsigned long old_rflags = vmx_get_rflags(vcpu); ---8<--- 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. Suggested-by: Nadav Amit Signed-off-by: Wanpeng Li [Wanpeng wrote the commit message with initial patch and Radim moved the update to vmx_set_rflags and added Paolo's suggestion for the check.] Signed-off-by: Radim Krčmář --- arch/x86/kvm/vmx.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 84e62acf2dd8..a776aea0043a 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -2326,6 +2326,11 @@ static void vmx_vcpu_put(struct kvm_vcpu *vcpu) __vmx_load_host_state(to_vmx(vcpu)); } +static bool emulation_required(struct kvm_vcpu *vcpu) +{ + return emulate_invalid_guest_state && !guest_state_valid(vcpu); +} + static void vmx_decache_cr0_guest_bits(struct kvm_vcpu *vcpu); /* @@ -2363,6 +2368,8 @@ static unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu) static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) { + unsigned long old_rflags = vmx_get_rflags(vcpu); + __set_bit(VCPU_EXREG_RFLAGS, (ulong *)&vcpu->arch.regs_avail); to_vmx(vcpu)->rflags = rflags; if (to_vmx(vcpu)->rmode.vm86_active) { @@ -2370,6 +2377,9 @@ static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) rflags |= X86_EFLAGS_IOPL | X86_EFLAGS_VM; } vmcs_writel(GUEST_RFLAGS, rflags); + + if ((old_rflags ^ rflags) & X86_EFLAGS_VM) + to_vmx(vcpu)->emulation_required = emulation_required(vcpu); } static u32 vmx_get_pkru(struct kvm_vcpu *vcpu) @@ -3857,11 +3867,6 @@ static __init int alloc_kvm_area(void) return 0; } -static bool emulation_required(struct kvm_vcpu *vcpu) -{ - return emulate_invalid_guest_state && !guest_state_valid(vcpu); -} - static void fix_pmode_seg(struct kvm_vcpu *vcpu, int seg, struct kvm_segment *save) { -- 2.13.2