From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-20.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 71B6BC433EF for ; Mon, 20 Sep 2021 18:27:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5D21660F23 for ; Mon, 20 Sep 2021 18:27:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1379197AbhITS2b (ORCPT ); Mon, 20 Sep 2021 14:28:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:44380 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1377967AbhITSWR (ORCPT ); Mon, 20 Sep 2021 14:22:17 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id ED402613D3; Mon, 20 Sep 2021 17:24:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1632158643; bh=66r49HTNwkwE+JMJG+EQWMjUJv8oQQa5yygb5WMrK88=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ym6chfVT1Ssk1n4Z7he4PlGnAvXL894JSxXFS6hYkrZ4qP/ivwnmVJm88frfGxfiL P4MOlG7Hq5V0qBPYK9QsXuBjx8vEAYVoqqTsn8PNXztF7Ec/EHCIhhUaN+wmsG3Ykz Pzyx6wj7XXJj12tEW3kaBYeaQXnd8uAUY9s32KlA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Oliver Upton , Marc Zyngier , Sasha Levin Subject: [PATCH 5.4 250/260] KVM: arm64: Handle PSCI resets before userspace touches vCPU state Date: Mon, 20 Sep 2021 18:44:28 +0200 Message-Id: <20210920163939.606845863@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210920163931.123590023@linuxfoundation.org> References: <20210920163931.123590023@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Oliver Upton [ Upstream commit 6826c6849b46aaa91300201213701eb861af4ba0 ] The CPU_ON PSCI call takes a payload that KVM uses to configure a destination vCPU to run. This payload is non-architectural state and not exposed through any existing UAPI. Effectively, we have a race between CPU_ON and userspace saving/restoring a guest: if the target vCPU isn't ran again before the VMM saves its state, the requested PC and context ID are lost. When restored, the target vCPU will be runnable and start executing at its old PC. We can avoid this race by making sure the reset payload is serviced before userspace can access a vCPU's state. Fixes: 358b28f09f0a ("arm/arm64: KVM: Allow a VCPU to fully reset itself") Signed-off-by: Oliver Upton Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20210818202133.1106786-3-oupton@google.com Signed-off-by: Sasha Levin --- virt/kvm/arm/arm.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c index 4af85605730e..f7150fbeeb55 100644 --- a/virt/kvm/arm/arm.c +++ b/virt/kvm/arm/arm.c @@ -1141,6 +1141,14 @@ long kvm_arch_vcpu_ioctl(struct file *filp, if (copy_from_user(®, argp, sizeof(reg))) break; + /* + * We could owe a reset due to PSCI. Handle the pending reset + * here to ensure userspace register accesses are ordered after + * the reset. + */ + if (kvm_check_request(KVM_REQ_VCPU_RESET, vcpu)) + kvm_reset_vcpu(vcpu); + if (ioctl == KVM_SET_ONE_REG) r = kvm_arm_set_reg(vcpu, ®); else -- 2.30.2