From nobody Mon Feb 9 11:28:11 2026 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 0DEEBC4321E for ; Wed, 30 Nov 2022 23:09:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229604AbiK3XJq (ORCPT ); Wed, 30 Nov 2022 18:09:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229686AbiK3XJk (ORCPT ); Wed, 30 Nov 2022 18:09:40 -0500 Received: from mail-oi1-x24a.google.com (mail-oi1-x24a.google.com [IPv6:2607:f8b0:4864:20::24a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A3AFC57B51 for ; Wed, 30 Nov 2022 15:09:39 -0800 (PST) Received: by mail-oi1-x24a.google.com with SMTP id c11-20020a056808138b00b0035a17dd854dso146845oiw.0 for ; Wed, 30 Nov 2022 15:09:39 -0800 (PST) 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=Ol+f04sMmomAVy3XzqNXK+ShxWrn6gIN96B7OKl5yaM=; b=S5armvpc10OdJc+V4p2ZjsfPOSB2+gt+Iv6GXjLvIxarCpnvSzXAszP1ZRQLfxrpVn 4VKntdMIRcH9d5x9XG1oGb5HbZFayk+JATeZBYQSlvM+DpwmfecZQ8AsDtvEHJv8Um6T UA3gJNgXD7v57R6+HWMBuEe+F5z07hORTUOLfSKyijFbwT8eHearvUCVMdt7/m5zjOT/ RJHYTQwmhGaPhaOc8DfHyXLVsjojQiPBCzNQuFpX8g3cosCwY+5F+o1XrOjsJNDhsv4X dI+LD+RMI6RHxUg1kkU/xRepaC5EvnuL3x5vvCzRlD3QPj+jjInfZWGepttgPw2FHtVt S1mQ== 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=Ol+f04sMmomAVy3XzqNXK+ShxWrn6gIN96B7OKl5yaM=; b=Zca+4tIyltacz7Yz8TM1UNQdUZJe8YgJc6ZakxwrD9ffT0MJZqz0ppdpJKW6o88NbL 0P8RlgyXPC4pcmHV2QKSnZ/sZbXZ0olPIIswFYp+8EJezeQn/YFn55Yh8B7qj/3hFTzT RG11GymHmcn9aShShW/dM0vLTW4AU2oU60iuBej0F6TV6E9wM5hfKwQN9OAyGXZQ3Tn0 CdJ6KgHedrecMc3hWDhwb5ghmqRevp5KeYhPGFKK1ARUq7wv5BSyhakWq4Le4vyDBjDX W2Qzib0QOyCT8tk6uC8ODTb7BsuPdjMZpX8p3Egxju4o61DdkHgz4QQpLVic/zvoi25c wAGA== X-Gm-Message-State: ANoB5pn9ot0olYM33sU3tEBL1gzyC8JBoNNLStHbMtDCwHG0B4Bvr2YK B8bcR1cYAiLdsAn4PBMgP8ECOje7FuY= X-Google-Smtp-Source: AA0mqf5M2pMTumXNgDe8Hfk4OhWDWk4TI1AuNKSU3xW+oTTlboWhE7bh5wRjvWcn8RwiB3BV7R0iM4jxw2w= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6870:bb1a:b0:143:74c2:f928 with SMTP id nw26-20020a056870bb1a00b0014374c2f928mr15086226oab.64.1669849778974; Wed, 30 Nov 2022 15:09:38 -0800 (PST) Reply-To: Sean Christopherson Date: Wed, 30 Nov 2022 23:08:45 +0000 In-Reply-To: <20221130230934.1014142-1-seanjc@google.com> Mime-Version: 1.0 References: <20221130230934.1014142-1-seanjc@google.com> X-Mailer: git-send-email 2.38.1.584.g0f3c55d4c2-goog Message-ID: <20221130230934.1014142-2-seanjc@google.com> Subject: [PATCH v2 01/50] 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 , David Woodhouse , Paul Durrant 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, Yuan Yao , Cornelia Huck , Isaku Yamahata , "=?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?=" , Fabiano Rosas , Michael Ellerman , Kai Huang , Chao Gao , Thomas Gleixner Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 1782c4555d94..b60abb03606b 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5919,12 +5919,6 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsig= ned vcpu_align, =20 kvm_chardev_ops.owner =3D module; =20 - r =3D misc_register(&kvm_dev); - if (r) { - pr_err("kvm: misc device register failed\n"); - goto out_unreg; - } - register_syscore_ops(&kvm_syscore_ops); =20 kvm_preempt_ops.sched_in =3D kvm_sched_in; @@ -5933,11 +5927,24 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsi= gned vcpu_align, kvm_init_debug(); =20 r =3D 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 =3D misc_register(&kvm_dev); + if (r) { + pr_err("kvm: misc device register failed\n"); + goto err_register; + } =20 return 0; =20 -out_unreg: +err_register: + kvm_vfio_ops_exit(); +err_vfio: kvm_async_pf_deinit(); out_free_4: for_each_possible_cpu(cpu) @@ -5963,8 +5970,14 @@ void kvm_exit(void) { int cpu; =20 - 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); --=20 2.38.1.584.g0f3c55d4c2-goog