Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966484AbcDLUxx (ORCPT ); Tue, 12 Apr 2016 16:53:53 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:50773 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966357AbcDLUxn (ORCPT ); Tue, 12 Apr 2016 16:53:43 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Yuki Shibuya , Paolo Bonzini , Kamal Mostafa Subject: [PATCH 4.2.y-ckt 31/70] KVM: x86: Inject pending interrupt even if pending nmi exist Date: Tue, 12 Apr 2016 13:52:16 -0700 Message-Id: <1460494375-30070-32-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1460494375-30070-1-git-send-email-kamal@canonical.com> References: <1460494375-30070-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 4.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2850 Lines: 74 4.2.8-ckt8 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Yuki Shibuya commit 321c5658c5e9192dea0d58ab67cf1791e45b2b26 upstream. Non maskable interrupts (NMI) are preferred to interrupts in current implementation. If a NMI is pending and NMI is blocked by the result of nmi_allowed(), pending interrupt is not injected and enable_irq_window() is not executed, even if interrupts injection is allowed. In old kernel (e.g. 2.6.32), schedule() is often called in NMI context. In this case, interrupts are needed to execute iret that intends end of NMI. The flag of blocking new NMI is not cleared until the guest execute the iret, and interrupts are blocked by pending NMI. Due to this, iret can't be invoked in the guest, and the guest is starved until block is cleared by some events (e.g. canceling injection). This patch injects pending interrupts, when it's allowed, even if NMI is blocked. And, If an interrupts is pending after executing inject_pending_event(), enable_irq_window() is executed regardless of NMI pending counter. Signed-off-by: Yuki Shibuya Suggested-by: Paolo Bonzini Signed-off-by: Paolo Bonzini Signed-off-by: Kamal Mostafa --- arch/x86/kvm/x86.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 9a16d3fd..382a150 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6141,12 +6141,10 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool req_int_win) } /* try to inject new event if pending */ - if (vcpu->arch.nmi_pending) { - if (kvm_x86_ops->nmi_allowed(vcpu)) { - --vcpu->arch.nmi_pending; - vcpu->arch.nmi_injected = true; - kvm_x86_ops->set_nmi(vcpu); - } + if (vcpu->arch.nmi_pending && kvm_x86_ops->nmi_allowed(vcpu)) { + --vcpu->arch.nmi_pending; + vcpu->arch.nmi_injected = true; + kvm_x86_ops->set_nmi(vcpu); } else if (kvm_cpu_has_injectable_intr(vcpu)) { /* * Because interrupts can be injected asynchronously, we are @@ -6550,10 +6548,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) if (inject_pending_event(vcpu, req_int_win) != 0) req_immediate_exit = true; /* enable NMI/IRQ window open exits if needed */ - else if (vcpu->arch.nmi_pending) - kvm_x86_ops->enable_nmi_window(vcpu); - else if (kvm_cpu_has_injectable_intr(vcpu) || req_int_win) - kvm_x86_ops->enable_irq_window(vcpu); + else { + if (vcpu->arch.nmi_pending) + kvm_x86_ops->enable_nmi_window(vcpu); + if (kvm_cpu_has_injectable_intr(vcpu) || req_int_win) + kvm_x86_ops->enable_irq_window(vcpu); + } if (kvm_lapic_enabled(vcpu)) { /* -- 2.7.4