From patchwork Tue Dec 22 09:55:18 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marc Zyngier X-Patchwork-Id: 7903341 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 929979F3CD for ; Tue, 22 Dec 2015 09:56:01 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id B00362042B for ; Tue, 22 Dec 2015 09:56:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B2395205B3 for ; Tue, 22 Dec 2015 09:55:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932233AbbLVJz5 (ORCPT ); Tue, 22 Dec 2015 04:55:57 -0500 Received: from foss.arm.com ([217.140.101.70]:52840 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932172AbbLVJzy (ORCPT ); Tue, 22 Dec 2015 04:55:54 -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 0BD085E2; Tue, 22 Dec 2015 01:55:28 -0800 (PST) Received: from localhost.localdomain (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2B2333F308; Tue, 22 Dec 2015 01:55:52 -0800 (PST) From: Marc Zyngier To: Christoffer Dall Cc: Shannon Zhao , kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: [PATCH 2/2] arm64: KVM: Do not update PC if the trap handler has updated it Date: Tue, 22 Dec 2015 09:55:18 +0000 Message-Id: <1450778118-12715-3-git-send-email-marc.zyngier@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1450778118-12715-1-git-send-email-marc.zyngier@arm.com> References: <1450778118-12715-1-git-send-email-marc.zyngier@arm.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Assuming we trap a system register, and decide that the access is illegal, we will inject an exception in the guest. In this case, we shouldn't increment the PC, or the vcpu will miss the first instruction of the handler, leading to a mildly confused guest. Solve this by snapshoting PC before the access is performed, and checking if it has moved or not before incrementing it. Reported-by: Shannon Zhao Signed-off-by: Marc Zyngier Tested-by: Shannon Zhao Reviewed-by: Shannon Zhao --- arch/arm64/kvm/sys_regs.c | 73 +++++++++++++++++++++++------------------------ 1 file changed, 36 insertions(+), 37 deletions(-) diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index d2650e8..9c87e0c 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -966,6 +966,39 @@ static const struct sys_reg_desc *find_reg(const struct sys_reg_params *params, return NULL; } +/* Perform the sysreg access, returns 0 on success */ +static int access_sys_reg(struct kvm_vcpu *vcpu, + struct sys_reg_params *params, + const struct sys_reg_desc *r) +{ + u64 pc = *vcpu_pc(vcpu); + + if (unlikely(!r)) + return -1; + + /* + * Not having an accessor means that we have configured a trap + * that we don't know how to handle. This certainly qualifies + * as a gross bug that should be fixed right away. + */ + BUG_ON(!r->access); + + if (likely(r->access(vcpu, params, r))) { + /* + * Skip the instruction if it was emulated without PC + * having changed. This allows us to detect a fault + * being injected (incrementing the PC here would + * cause the vcpu to skip the first instruction of its + * fault handler). + */ + if (pc == *vcpu_pc(vcpu)) + kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu)); + return 0; + } + + return -1; +} + int kvm_handle_cp14_load_store(struct kvm_vcpu *vcpu, struct kvm_run *run) { kvm_inject_undefined(vcpu); @@ -994,26 +1027,7 @@ static int emulate_cp(struct kvm_vcpu *vcpu, r = find_reg(params, table, num); - if (r) { - /* - * Not having an accessor means that we have - * configured a trap that we don't know how to - * handle. This certainly qualifies as a gross bug - * that should be fixed right away. - */ - BUG_ON(!r->access); - - if (likely(r->access(vcpu, params, r))) { - /* Skip instruction, since it was emulated */ - kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu)); - } - - /* Handled */ - return 0; - } - - /* Not handled */ - return -1; + return access_sys_reg(vcpu, params, r); } static void unhandled_cp_access(struct kvm_vcpu *vcpu, @@ -1178,27 +1192,12 @@ static int emulate_sys_reg(struct kvm_vcpu *vcpu, if (!r) r = find_reg(params, sys_reg_descs, ARRAY_SIZE(sys_reg_descs)); - if (likely(r)) { - /* - * Not having an accessor means that we have - * configured a trap that we don't know how to - * handle. This certainly qualifies as a gross bug - * that should be fixed right away. - */ - BUG_ON(!r->access); - - if (likely(r->access(vcpu, params, r))) { - /* Skip instruction, since it was emulated */ - kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu)); - return 1; - } - /* If access function fails, it should complain. */ - } else { + if (access_sys_reg(vcpu, params, r)) { kvm_err("Unsupported guest sys_reg access at: %lx\n", *vcpu_pc(vcpu)); print_sys_reg_instr(params); + kvm_inject_undefined(vcpu); } - kvm_inject_undefined(vcpu); return 1; }