From patchwork Thu Apr 25 12:57:40 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andre Przywara X-Patchwork-Id: 10916979 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B1DC792A for ; Thu, 25 Apr 2019 12:57:53 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9DC2A2811E for ; Thu, 25 Apr 2019 12:57:53 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8CEE328528; Thu, 25 Apr 2019 12:57:53 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 266022811E for ; Thu, 25 Apr 2019 12:57:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727654AbfDYM5v (ORCPT ); Thu, 25 Apr 2019 08:57:51 -0400 Received: from foss.arm.com ([217.140.101.70]:43386 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727168AbfDYM5v (ORCPT ); Thu, 25 Apr 2019 08:57:51 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C9C81A78; Thu, 25 Apr 2019 05:57:50 -0700 (PDT) Received: from donnerap.arm.com (donnerap.cambridge.arm.com [10.1.197.44]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 87FAC3F5C1; Thu, 25 Apr 2019 05:57:49 -0700 (PDT) From: Andre Przywara To: Marc Zyngier , Christoffer Dall Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org Subject: [PATCH] KVM: arm/arm64: Don't emulate virtual timers on userspace ioctls Date: Thu, 25 Apr 2019 13:57:40 +0100 Message-Id: <20190425125740.238036-1-andre.przywara@arm.com> X-Mailer: git-send-email 2.17.1 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Christoffer Dall When a VCPU never runs before a guest exists, but we set timer registers up via ioctls, the associated hrtimer might never get cancelled. Since we moved vcpu_load/put into the arch-specific implementations and only have load/put for KVM_RUN, we won't ever have a scheduled hrtimer for emulating a timer when modifying the timer state via an ioctl from user space. All we need to do is make sure that we pick up the right state when we load the timer state next time userspace calls KVM_RUN again. We also do not need to worry about this interacting with the bg_timer, because if we were in WFI from the guest, and somehow ended up in a kvm_arm_timer_set_reg, it means that: 1. the VCPU thread has received a signal, 2. we have called vcpu_load when being scheduled in again, 3. we have called vcpu_put when we returned to userspace for it to issue another ioctl And therefore will not have a bg_timer programmed and the event is treated as a spurious wakeup from WFI if userspace decides to run the vcpu again even if there are not virtual interrupts. This fixes stray virtual timer interrupts triggered by an expiring hrtimer, which happens after a failed live migration, for instance. Signed-off-by: Christoffer Dall Reported-by: Andre Przywara Tested-by: Andre Przywara Signed-off-by: Andre Przywara --- virt/kvm/arm/arch_timer.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c index 3417f2dbc366..3538bc39a87a 100644 --- a/virt/kvm/arm/arch_timer.c +++ b/virt/kvm/arm/arch_timer.c @@ -507,6 +507,14 @@ static void kvm_timer_vcpu_load_nogic(struct kvm_vcpu *vcpu) { struct arch_timer_context *vtimer = vcpu_vtimer(vcpu); + /* + * Update the timer output so that it is likely to match the + * state we're about to restore. If the timer expires between + * this point and the register restoration, we'll take the + * interrupt anyway. + */ + kvm_timer_update_irq(vcpu, kvm_timer_should_fire(vtimer), vtimer); + /* * When using a userspace irqchip with the architected timers and a * host interrupt controller that doesn't support an active state, we @@ -730,7 +738,6 @@ static void kvm_timer_init_interrupt(void *info) int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, u64 regid, u64 value) { struct arch_timer_context *timer; - bool level; switch (regid) { case KVM_REG_ARM_TIMER_CTL: @@ -758,10 +765,6 @@ int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, u64 regid, u64 value) return -1; } - level = kvm_timer_should_fire(timer); - kvm_timer_update_irq(vcpu, level, timer); - timer_emulate(timer); - return 0; }