From patchwork Fri Jan 31 16:37:20 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexandru Elisei X-Patchwork-Id: 11360253 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A100092A for ; Fri, 31 Jan 2020 16:38:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 88B4D2253D for ; Fri, 31 Jan 2020 16:38:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726712AbgAaQiL (ORCPT ); Fri, 31 Jan 2020 11:38:11 -0500 Received: from foss.arm.com ([217.140.110.172]:37326 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726139AbgAaQiL (ORCPT ); Fri, 31 Jan 2020 11:38:11 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A0C8FFEC; Fri, 31 Jan 2020 08:38:10 -0800 (PST) Received: from e123195-lin.cambridge.arm.com (e123195-lin.cambridge.arm.com [10.1.196.63]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id A00093F68E; Fri, 31 Jan 2020 08:38:09 -0800 (PST) From: Alexandru Elisei To: kvm@vger.kernel.org Cc: pbonzini@redhat.com, drjones@redhat.com, maz@kernel.org, andre.przywara@arm.com, vladimir.murzin@arm.com, mark.rutland@arm.com Subject: [kvm-unit-tests PATCH v4 02/10] arm/arm64: psci: Don't run C code without stack or vectors Date: Fri, 31 Jan 2020 16:37:20 +0000 Message-Id: <20200131163728.5228-3-alexandru.elisei@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200131163728.5228-1-alexandru.elisei@arm.com> References: <20200131163728.5228-1-alexandru.elisei@arm.com> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org The psci test performs a series of CPU_ON/CPU_OFF cycles for CPU 1. This is done by setting the entry point for the CPU_ON call to the physical address of the C function cpu_psci_cpu_die. The compiler is well within its rights to use the stack when generating code for cpu_psci_cpu_die. However, because no stack initialization has been done, the stack pointer is zero, as set by KVM when creating the VCPU. This causes a data abort without a change in exception level. The VBAR_EL1 register is also zero (the KVM reset value for VBAR_EL1), the MMU is off, and we end up trying to fetch instructions from address 0x200. At this point, a stage 2 instruction abort is generated which is taken to KVM. KVM interprets this as an instruction fetch from an I/O region, and injects a prefetch abort into the guest. Prefetch abort is a synchronous exception, and on guest return the VCPU PC will be set to VBAR_EL1 + 0x200, which is... 0x200. The VCPU ends up in an infinite loop causing a prefetch abort while fetching the instruction to service the said abort. To avoid all of this, lets use the assembly function halt as the CPU_ON entry address. Also, expand the check to test that we only get PSCI_RET_SUCCESS exactly once, as we're never offlining the CPU during the test. Signed-off-by: Alexandru Elisei --- arm/psci.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/arm/psci.c b/arm/psci.c index 5c1accb6cea4..ffc09a2e9858 100644 --- a/arm/psci.c +++ b/arm/psci.c @@ -79,13 +79,14 @@ static void cpu_on_secondary_entry(void) cpumask_set_cpu(cpu, &cpu_on_ready); while (!cpu_on_start) cpu_relax(); - cpu_on_ret[cpu] = psci_cpu_on(cpus[1], __pa(cpu_psci_cpu_die)); + cpu_on_ret[cpu] = psci_cpu_on(cpus[1], __pa(halt)); cpumask_set_cpu(cpu, &cpu_on_done); } static bool psci_cpu_on_test(void) { bool failed = false; + int ret_success = 0; int cpu; cpumask_set_cpu(1, &cpu_on_ready); @@ -104,7 +105,7 @@ static bool psci_cpu_on_test(void) cpu_on_start = 1; smp_mb(); - cpu_on_ret[0] = psci_cpu_on(cpus[1], __pa(cpu_psci_cpu_die)); + cpu_on_ret[0] = psci_cpu_on(cpus[1], __pa(halt)); cpumask_set_cpu(0, &cpu_on_done); while (!cpumask_full(&cpu_on_done)) @@ -113,12 +114,19 @@ static bool psci_cpu_on_test(void) for_each_present_cpu(cpu) { if (cpu == 1) continue; - if (cpu_on_ret[cpu] != PSCI_RET_SUCCESS && cpu_on_ret[cpu] != PSCI_RET_ALREADY_ON) { + if (cpu_on_ret[cpu] == PSCI_RET_SUCCESS) { + ret_success++; + } else if (cpu_on_ret[cpu] != PSCI_RET_ALREADY_ON) { report_info("unexpected cpu_on return value: caller=CPU%d, ret=%d", cpu, cpu_on_ret[cpu]); failed = true; } } + if (ret_success != 1) { + report_info("got %d CPU_ON success", ret_success); + failed = true; + } + return !failed; }