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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6F78CC7EE2F for ; Fri, 2 Jun 2023 23:33:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236920AbjFBXdN (ORCPT ); Fri, 2 Jun 2023 19:33:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49728 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236868AbjFBXdJ (ORCPT ); Fri, 2 Jun 2023 19:33:09 -0400 Received: from mail-pg1-x549.google.com (mail-pg1-x549.google.com [IPv6:2607:f8b0:4864:20::549]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 79C70E42 for ; Fri, 2 Jun 2023 16:33:08 -0700 (PDT) Received: by mail-pg1-x549.google.com with SMTP id 41be03b00d2f7-5341081a962so2545754a12.2 for ; Fri, 02 Jun 2023 16:33:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1685748788; x=1688340788; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=j6nYf/jOBntGS2igA5vSyIxcer0Y2dnZYEhcRt0bNGM=; b=Wi3H0k9BpFJWJAoAjhZGH+/ORYMPc9rbgUFp0V7StYibnfR5Xj/2eL6uRo+vy2ORjC t7IhWOLboZOtaFGAZUE5ovIvkiLsDV+67SAoJ01MJRK09U02fJoLAa4AUpOGsfC1kS7P +hjP1kmcc8hDU9rMT9LiNwBTg5BYbmCeWKvHScZv9HRM/kblDg9yNpxucaTAI3D5S7nI jQFbapqcnP3k3m32lzqRcCZH4s+IoewCx1fJp3P83YZ2/GpgKpGBLg6fcwxRiNZHIxPk 9nAJ5vbHtv8f6sqcuBQySNHOow5IdMVwxGuFB065jqUKW3dyVjnL9DouUtA0ENGMulPM nIDg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1685748788; x=1688340788; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=j6nYf/jOBntGS2igA5vSyIxcer0Y2dnZYEhcRt0bNGM=; b=YqPuFCDhItDZxy0q83PdUcbPNCPjDnOJjN+dihlzBu90CHQJybPv0KmIYc8egD4Ymm 1yhKcRaFzDQawk41GNMXdq8rl4DCIo+sQaaI3kZ2aBQSXBimuuv9qGu++21c9EOGxku/ Kxpkqc/dQHLBul+5HjbJjrlxXTgjSlrrIMuwsbwT5eheDXR5os00jmV3VlOYij3OdCtN iYsuMz+kiyf6+vIfYr/J+drrywcPyjpF4wERmVv9/Tw9twvT8dg0fYU7mzK5pUCcJQV/ p4CkNhdMwnycpNWzUWLZLSksHCfRgeXbS5feZ+YFKIyb8MXMbCyGahg0yEEiCsgTni0b arJA== X-Gm-Message-State: AC+VfDx6/MpHYu9UVd0LExuiHMVEGF8Y/p7Ovf9rEJZaOuG8RKTSGAWz NqLakcXq4WKI0ztNOG6Ajja34mp1Vos= X-Google-Smtp-Source: ACHHUZ5RQW9bPamlFEzYIenvVcUlgxBxW5xO/KEOYWb6HOpyK20P4kwc3nv+mQDuMb0Bq7zPa45xizLoZzA= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a65:4284:0:b0:542:96b5:b5e4 with SMTP id j4-20020a654284000000b0054296b5b5e4mr648446pgp.11.1685748787993; Fri, 02 Jun 2023 16:33:07 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 2 Jun 2023 16:32:50 -0700 In-Reply-To: <20230602233250.1014316-1-seanjc@google.com> Mime-Version: 1.0 References: <20230602233250.1014316-1-seanjc@google.com> X-Mailer: git-send-email 2.41.0.rc2.161.g9c6817b8e7-goog Message-ID: <20230602233250.1014316-4-seanjc@google.com> Subject: [PATCH v3 3/3] KVM: selftests: Add test for race in kvm_recalculate_apic_map() From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Michal Luczaj Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Michal Luczaj Keep switching between LAPIC_MODE_X2APIC and LAPIC_MODE_DISABLED during APIC map construction to hunt for TOCTOU bugs in KVM. KVM's optimized map recalc makes multiple passes over the list of vCPUs, and the calculations ignore vCPU's whose APIC is hardware-disabled, i.e. there's a window where toggling LAPIC_MODE_DISABLED is quite interesting. Signed-off-by: Michal Luczaj Co-developed-by: Sean Christopherson Signed-off-by: Sean Christopherson --- tools/testing/selftests/kvm/Makefile | 1 + .../kvm/x86_64/recalc_apic_map_test.c | 74 +++++++++++++++++++ 2 files changed, 75 insertions(+) create mode 100644 tools/testing/selftests/kvm/x86_64/recalc_apic_map_test.c diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile index 7a5ff646e7e7..4761b768b773 100644 --- a/tools/testing/selftests/kvm/Makefile +++ b/tools/testing/selftests/kvm/Makefile @@ -116,6 +116,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/sev_migrate_tests TEST_GEN_PROGS_x86_64 += x86_64/amx_test TEST_GEN_PROGS_x86_64 += x86_64/max_vcpuid_cap_test TEST_GEN_PROGS_x86_64 += x86_64/triple_fault_event_test +TEST_GEN_PROGS_x86_64 += x86_64/recalc_apic_map_test TEST_GEN_PROGS_x86_64 += access_tracking_perf_test TEST_GEN_PROGS_x86_64 += demand_paging_test TEST_GEN_PROGS_x86_64 += dirty_log_test diff --git a/tools/testing/selftests/kvm/x86_64/recalc_apic_map_test.c b/tools/testing/selftests/kvm/x86_64/recalc_apic_map_test.c new file mode 100644 index 000000000000..4c416ebe7d66 --- /dev/null +++ b/tools/testing/selftests/kvm/x86_64/recalc_apic_map_test.c @@ -0,0 +1,74 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Test edge cases and race conditions in kvm_recalculate_apic_map(). + */ + +#include +#include +#include + +#include "processor.h" +#include "test_util.h" +#include "kvm_util.h" +#include "apic.h" + +#define TIMEOUT 5 /* seconds */ + +#define LAPIC_DISABLED 0 +#define LAPIC_X2APIC (MSR_IA32_APICBASE_ENABLE | X2APIC_ENABLE) +#define MAX_XAPIC_ID 0xff + +static void *race(void *arg) +{ + struct kvm_lapic_state lapic = {}; + struct kvm_vcpu *vcpu = arg; + + while (1) { + /* Trigger kvm_recalculate_apic_map(). */ + vcpu_ioctl(vcpu, KVM_SET_LAPIC, &lapic); + pthread_testcancel(); + } + + return NULL; +} + +int main(void) +{ + struct kvm_vcpu *vcpus[KVM_MAX_VCPUS]; + struct kvm_vcpu *vcpuN; + struct kvm_vm *vm; + pthread_t thread; + time_t t; + int i; + + kvm_static_assert(KVM_MAX_VCPUS > MAX_XAPIC_ID); + + /* + * Create the max number of vCPUs supported by selftests so that KVM + * has decent amount of work to do when recalculating the map, i.e. to + * make the problematic window large enough to hit. + */ + vm = vm_create_with_vcpus(KVM_MAX_VCPUS, NULL, vcpus); + + /* + * Enable x2APIC on all vCPUs so that KVM doesn't bail from the recalc + * due to vCPUs having aliased xAPIC IDs (truncated to 8 bits). + */ + for (i = 0; i < KVM_MAX_VCPUS; i++) + vcpu_set_msr(vcpus[i], MSR_IA32_APICBASE, LAPIC_X2APIC); + + ASSERT_EQ(pthread_create(&thread, NULL, race, vcpus[0]), 0); + + vcpuN = vcpus[KVM_MAX_VCPUS - 1]; + for (t = time(NULL) + TIMEOUT; time(NULL) < t;) { + vcpu_set_msr(vcpuN, MSR_IA32_APICBASE, LAPIC_X2APIC); + vcpu_set_msr(vcpuN, MSR_IA32_APICBASE, LAPIC_DISABLED); + } + + ASSERT_EQ(pthread_cancel(thread), 0); + ASSERT_EQ(pthread_join(thread, NULL), 0); + + kvm_vm_free(vm); + + return 0; +} -- 2.41.0.rc2.161.g9c6817b8e7-goog