From patchwork Fri Jan 25 09:46:52 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoffer Dall X-Patchwork-Id: 10780849 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 E58C691E for ; Fri, 25 Jan 2019 09:47:04 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D33BC2F818 for ; Fri, 25 Jan 2019 09:47:04 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id C68302F8A3; Fri, 25 Jan 2019 09:47:04 +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 68C232F818 for ; Fri, 25 Jan 2019 09:47:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728330AbfAYJrD (ORCPT ); Fri, 25 Jan 2019 04:47:03 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:43816 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727689AbfAYJrD (ORCPT ); Fri, 25 Jan 2019 04:47:03 -0500 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 E96D5EBD; Fri, 25 Jan 2019 01:47:02 -0800 (PST) Received: from localhost (e113682-lin.copenhagen.arm.com [10.32.144.41]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7590D3F589; Fri, 25 Jan 2019 01:47:02 -0800 (PST) From: Christoffer Dall To: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Cc: kvm@vger.kernel.org, Christoffer Dall , Marc Zyngier Subject: [PATCH 1/5] KVM: arm/arm64: Reset the VCPU without preemption and vcpu state loaded Date: Fri, 25 Jan 2019 10:46:52 +0100 Message-Id: <20190125094656.5026-2-christoffer.dall@arm.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20190125094656.5026-1-christoffer.dall@arm.com> References: <20190125094656.5026-1-christoffer.dall@arm.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Resetting the VCPU state modifies the system register state in memory, but this may interact with vcpu_load/vcpu_put if running with preemption disabled, which in turn may lead to corrupted system register state. Address this by disabling preemption and doing put/load if required around the reset logic. Signed-off-by: Christoffer Dall Signed-off-by: Marc Zyngier Reviewed-by: Andrew Jones --- arch/arm64/kvm/reset.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c index b72a3dd56204..f21a2a575939 100644 --- a/arch/arm64/kvm/reset.c +++ b/arch/arm64/kvm/reset.c @@ -105,16 +105,33 @@ int kvm_arch_vm_ioctl_check_extension(struct kvm *kvm, long ext) * This function finds the right table above and sets the registers on * the virtual CPU struct to their architecturally defined reset * values. + * + * Note: This function can be called from two paths: The KVM_ARM_VCPU_INIT + * ioctl or as part of handling a request issued by another VCPU in the PSCI + * handling code. In the first case, the VCPU will not be loaded, and in the + * second case the VCPU will be loaded. Because this function operates purely + * on the memory-backed valus of system registers, we want to do a full put if + * we were loaded (handling a request) and load the values back at the end of + * the function. Otherwise we leave the state alone. In both cases, we + * disable preemption around the vcpu reset as we would otherwise race with + * preempt notifiers which also call put/load. */ int kvm_reset_vcpu(struct kvm_vcpu *vcpu) { const struct kvm_regs *cpu_reset; + int ret = -EINVAL; + bool loaded; + + preempt_disable(); + loaded = (vcpu->cpu != -1); + if (loaded) + kvm_arch_vcpu_put(vcpu); switch (vcpu->arch.target) { default: if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features)) { if (!cpu_has_32bit_el1()) - return -EINVAL; + goto out; cpu_reset = &default_regs_reset32; } else { cpu_reset = &default_regs_reset; @@ -137,7 +154,12 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu) vcpu->arch.workaround_flags |= VCPU_WORKAROUND_2_FLAG; /* Reset timer */ - return kvm_timer_vcpu_reset(vcpu); + ret = kvm_timer_vcpu_reset(vcpu); +out: + if (loaded) + kvm_arch_vcpu_load(vcpu, smp_processor_id()); + preempt_enable(); + return ret; } void kvm_set_ipa_limit(void)