From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: [PATCHv2] KVM: prevent spurious exit to userspace during task switch emulation. Date: Thu, 15 Apr 2010 13:09:05 +0300 Message-ID: <20100415100905.GA4550@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: avi@redhat.com, mtosatti@redhat.com To: kvm@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:1422 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751630Ab0DOKJH (ORCPT ); Thu, 15 Apr 2010 06:09:07 -0400 Received: from int-mx05.intmail.prod.int.phx2.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.18]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o3FA97jw024278 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Thu, 15 Apr 2010 06:09:07 -0400 Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: If kvm_task_switch() fails code exits to userspace without specifying exit reason, so the previous exit reason is reused by userspace. Fix this by specifying exit reason correctly. --- Changelog: v1->v2: - report emulation error to userspace instead of ignoring it silently. Should be applied after "KVM: fix emulator_task_switch() return value." since it relies on new return value from kvm_task_switch(). Signed-off-by: Gleb Natapov diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index c773a46..4a7a9ff 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -2254,7 +2254,13 @@ static int task_switch_interception(struct vcpu_svm *svm) (int_vec == OF_VECTOR || int_vec == BP_VECTOR))) skip_emulated_instruction(&svm->vcpu); - return kvm_task_switch(&svm->vcpu, tss_selector, reason); + if (kvm_task_switch(&svm->vcpu, tss_selector, reason) == EMULATE_FAIL) { + svm->vcpu.run->exit_reason = KVM_EXIT_INTERNAL_ERROR; + svm->vcpu.run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION; + svm->vcpu.run->internal.ndata = 0; + return 0; + } + return 1; } static int cpuid_interception(struct vcpu_svm *svm) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 453f080..9517cbc 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -3306,8 +3306,12 @@ static int handle_task_switch(struct kvm_vcpu *vcpu) type != INTR_TYPE_NMI_INTR)) skip_emulated_instruction(vcpu); - if (!kvm_task_switch(vcpu, tss_selector, reason)) + if (kvm_task_switch(vcpu, tss_selector, reason) == EMULATE_FAIL) { + vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; + vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION; + vcpu->run->internal.ndata = 0; return 0; + } /* clear all local breakpoint enable flags */ vmcs_writel(GUEST_DR7, vmcs_readl(GUEST_DR7) & ~55); -- Gleb.