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[2620:137:e000::1:20]) by mx.google.com with ESMTP id y15-20020a63494f000000b0046fe64444fcsi8698107pgk.839.2022.11.02.16.21.08; Wed, 02 Nov 2022 16:21:21 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20210112 header.b="Y/LgcbOS"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230324AbiKBXT2 (ORCPT + 99 others); Wed, 2 Nov 2022 19:19:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60860 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230197AbiKBXTU (ORCPT ); Wed, 2 Nov 2022 19:19:20 -0400 Received: from mail-yw1-x1149.google.com (mail-yw1-x1149.google.com [IPv6:2607:f8b0:4864:20::1149]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 804EC21B1 for ; Wed, 2 Nov 2022 16:19:17 -0700 (PDT) Received: by mail-yw1-x1149.google.com with SMTP id 00721157ae682-37010fefe48so538177b3.19 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=C2FndJmlVwZN1m/yODAejZH5iVfD2FuSrdfZj69zDO85EzVND2YR4MAJBHXJkSkxvJ fcMS8iKRuF/0+dt9LJMh7oboDY92EtHJRSUztZRTDmR5puxxpWel6kRKSCdFJ7DUI90R ZXsc4jenRibJYul3O8epShTwSNBom7TDQtgmg7sjooX7/9cfoccgh0Ynt0EArZGEQilp MYLnfOH/Z8ATdfvTLqTq31JcgajIGiHQWyczy8Or11ObK4LWJCOpx88ypHUkCuSqTyEh frZWdvbOVfJGgcxj1ecZVu2/h+KARpSoHB5xmiqa65atW3rCr9ryrck/ncDfAWJiD3Le GMLw== X-Gm-Message-State: ACrzQf0WSqc9rRQR5tgBlbP482fFmjucQTtvglRvs9dGLzQN4xAkPNTf eZ82QXeYZCke1PAjAlMxTuVVO+Wv5Rg= 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 X-Spam-Status: No, score=-9.6 required=5.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1748428422858879375?= X-GMAIL-MSGID: =?utf-8?q?1748428422858879375?= 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);