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 73778C433FE for ; Wed, 2 Nov 2022 23:19:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230315AbiKBXT2 (ORCPT ); Wed, 2 Nov 2022 19:19:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60864 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230211AbiKBXTU (ORCPT ); Wed, 2 Nov 2022 19:19:20 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 83C2521B3 for ; Wed, 2 Nov 2022 16:19:17 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-36bf9c132f9so912207b3.8 for ; Wed, 02 Nov 2022 16:19:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; 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=J4baT2gCaqaG+hAt/mJp+w8Lapt4XhULv2rUZ1lbod8=; b=Y/LgcbOSvwbnzJXRGal3Ep3KB7/0yCP9cU65YkQert5+3hLyHHSjjMao2/UuV8Y1pm rxtzoLchmx+Mfw2uDAT2cc7aUI/oVviLkjgjK/axQ+ux0UramBaUfpMh7qr3oHRIrkbM g29/HkiYkyDP9zLb6T5zYBFWjCRhk7uodXh+YwW0fknC8LCiXKsmBrjDcUEU31+Wr1aB IkpbU9xq9Vh5sCGgS87jUUdeWGvPSndSpQtpQaJwtmMAXoArYlfZq/YuY0lzlwpeE7m/ iktR7kaNiirOlR+WEM+Xzua+uL8FsQlW7DYdB778CLiAWY7J4Sab6pQ6XIRdRfFvya7C dqQw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; 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=J4baT2gCaqaG+hAt/mJp+w8Lapt4XhULv2rUZ1lbod8=; b=NdZcueDThM9ugh5ck00cEb4Ov/MO8CJHrQheXTBTvXvXAZjwar5wp+tqwDiJEzF7Wd QrxX8QXS7j2yIfAcZPOuUCO7qArcMrZRobMdDa3UH6092GY0oQ2QeSxt+W30XPbcSWhs Y6aiVMzsBmn2ogfWEDxH93jQytghOSDMBNW453IqbUVIEpQugrBQzPn0+Pg9p8+VHMQ6 vMZFgmkvEuopLoF3Sn3oZgMdd+ME291AvBigwFPIMS1L6k46bxuaPWW0vmtw7RjuScL1 XvrL3obmmFZnPB3LbLwLZaxLPt/jfLhRgI3ikZpZcqAjoaa7Y6xMbfkuhUPdnAGAG316 rnWQ== X-Gm-Message-State: ACrzQf1wopI2aXrKMNuQ79vKzEjlFU60XTuLztzp+Ya4faSio0tkD/Fw Pb/brATg52eoHBuaXGR4aDs1fhvLP+c= X-Google-Smtp-Source: AMsMyM5o6mEhEhiYREiqHX2O6l5zHbOoOJ5LkmkQQCrMnpzWAr9BhETh9np1j3huSYRmzTw5GjJ2jYjKldE= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a25:f451:0:b0:6cc:aeeb:8fed with SMTP id p17-20020a25f451000000b006ccaeeb8fedmr15718187ybe.11.1667431156834; Wed, 02 Nov 2022 16:19:16 -0700 (PDT) Reply-To: Sean Christopherson Date: Wed, 2 Nov 2022 23:18:28 +0000 In-Reply-To: <20221102231911.3107438-1-seanjc@google.com> Mime-Version: 1.0 References: <20221102231911.3107438-1-seanjc@google.com> X-Mailer: git-send-email 2.38.1.431.g37b22c650d-goog Message-ID: <20221102231911.3107438-2-seanjc@google.com> Subject: [PATCH 01/44] KVM: Register /dev/kvm as the _very_ last thing during initialization From: Sean Christopherson To: Paolo Bonzini , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Matthew Rosato , Eric Farman , Sean Christopherson , Vitaly Kuznetsov Cc: James Morse , Alexandru Elisei , Suzuki K Poulose , Oliver Upton , Atish Patra , David Hildenbrand , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Isaku Yamahata , Fabiano Rosas , Michael Ellerman , Chao Gao , Thomas Gleixner , Yuan Yao Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org Register /dev/kvm, i.e. expose KVM to userspace, only after all other setup has completed. Once /dev/kvm is exposed, userspace can start invoking KVM ioctls, creating VMs, etc... If userspace creates a VM before KVM is done with its configuration, bad things may happen, e.g. KVM will fail to properly migrate vCPU state if a VM is created before KVM has registered preemption notifiers. Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson --- virt/kvm/kvm_main.c | 31 ++++++++++++++++++++++--------- 1 file changed, 22 insertions(+), 9 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index f1df24c2bc84..a188d27f78af 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5900,12 +5900,6 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align, kvm_chardev_ops.owner = module; - r = misc_register(&kvm_dev); - if (r) { - pr_err("kvm: misc device register failed\n"); - goto out_unreg; - } - register_syscore_ops(&kvm_syscore_ops); kvm_preempt_ops.sched_in = kvm_sched_in; @@ -5914,11 +5908,24 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align, kvm_init_debug(); r = kvm_vfio_ops_init(); - WARN_ON(r); + if (WARN_ON_ONCE(r)) + goto err_vfio; + + /* + * Registration _must_ be the very last thing done, as this exposes + * /dev/kvm to userspace, i.e. all infrastructure must be setup! + */ + r = misc_register(&kvm_dev); + if (r) { + pr_err("kvm: misc device register failed\n"); + goto err_register; + } return 0; -out_unreg: +err_register: + kvm_vfio_ops_exit(); +err_vfio: kvm_async_pf_deinit(); out_free_4: for_each_possible_cpu(cpu) @@ -5944,8 +5951,14 @@ void kvm_exit(void) { int cpu; - debugfs_remove_recursive(kvm_debugfs_dir); + /* + * Note, unregistering /dev/kvm doesn't strictly need to come first, + * fops_get(), a.k.a. try_module_get(), prevents acquiring references + * to KVM while the module is being stopped. + */ misc_deregister(&kvm_dev); + + debugfs_remove_recursive(kvm_debugfs_dir); for_each_possible_cpu(cpu) free_cpumask_var(per_cpu(cpu_kick_mask, cpu)); kmem_cache_destroy(kvm_vcpu_cache); -- 2.38.1.431.g37b22c650d-goog