From nobody Tue Feb 10 06:05:33 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 C0328C77B7C for ; Fri, 12 May 2023 23:50:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240932AbjELXuo (ORCPT ); Fri, 12 May 2023 19:50:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50970 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240881AbjELXug (ORCPT ); Fri, 12 May 2023 19:50:36 -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 BE049269E for ; Fri, 12 May 2023 16:50:34 -0700 (PDT) Received: by mail-yw1-x1149.google.com with SMTP id 00721157ae682-559d8e22306so189775167b3.1 for ; Fri, 12 May 2023 16:50:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1683935434; x=1686527434; 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=nr0/2P0PrhPVltPxqFEO8yZGlq+w0+NW5S2btIKs8As=; b=WnOy9eWYFT1JeIO58JaMN1jZcMhT11BdOKPnALDAvrjMuhmZH42P9YhiZa/7JYaYGY ZpHrwciGnurOfJK9oBMXECwzcbEmpZfTWoGPFiZvJ8gE7xDpEIqA+FoxYyfH6y7DyEbJ +lNK1HZAQoGu6aWxcQqJxEpOkzAtMrWoFOh0Eelr1BaB+ZGd4k5UOiGGNYp9UpCi9D+z K5up0w1/ftbLw4OwW15WahGKHXE4yaa6gTWI6h7md8aEWjTJaNNiXhCLCQ9EeQlXZjhk M+9AdiXDgGvYOgot5GgzVAVDi+/PP32mF4DqfsRGOyX3UZkUQ2COmITahoXI/TtRngN+ mU6g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1683935434; x=1686527434; 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=nr0/2P0PrhPVltPxqFEO8yZGlq+w0+NW5S2btIKs8As=; b=UnTt5ePcBdS9r3T3SyJ5vA4UMdA0oeOMagL7775fBqP5m3yMac1t5kqBn7HPEb0aku l8N8vq6lC2od77aNUp0bTSuvdY2DID/RT2Id94mHdQHjAz871yKYlozB/F+6D/iX5Rlp +Fvbl/Il1KDmo4bOMw/Ox0vDVi8psVGXUuhf+/Oxf6clMf+uzCVrD42CP92X8XYVt9c/ 7P0BHE4btYFsJgzZVWn0BDoL5KiNOSthuWY7knatFbmmvievx8dxLsS0wX+SI0sYWHO+ 7UgaMIrDUPBWMO87469iToQBRmlPaFORuzpZw2JAjAT+8+yGcVHO/vlTaGaXNuddQ+Nc ULxQ== X-Gm-Message-State: AC+VfDwHiQjKgpfUtgEADnWx3/g8BI2Yo1xMlWlpNSeH02d/6OUstHxB wU81hvJbN9JLH1OCY05+AZY0mq3AL8g= X-Google-Smtp-Source: ACHHUZ5fCcu/o8G8jp7gcUKE/IEMSr5CBYWwKcUGKW1V18cr7ZFI2S5aWNKXh3lhFT3tw6R83mDt0fyaSK8= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a81:ca49:0:b0:55d:9484:f153 with SMTP id y9-20020a81ca49000000b0055d9484f153mr16043474ywk.7.1683935434025; Fri, 12 May 2023 16:50:34 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 12 May 2023 16:50:10 -0700 In-Reply-To: <20230512235026.808058-1-seanjc@google.com> Mime-Version: 1.0 References: <20230512235026.808058-1-seanjc@google.com> X-Mailer: git-send-email 2.40.1.606.ga4b1b128d6-goog Message-ID: <20230512235026.808058-3-seanjc@google.com> Subject: [PATCH v3 02/18] x86/reboot: Harden virtualization hooks for emergency reboot From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Andrew Cooper , Kai Huang , Chao Gao Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Provide dedicated helpers to (un)register virt hooks used during an emergency crash/reboot, and WARN if there is an attempt to overwrite the registered callback, or an attempt to do an unpaired unregister. Opportunsitically use rcu_assign_pointer() instead of RCU_INIT_POINTER(), mainly so that the set/unset paths are more symmetrical, but also because any performance gains from using RCU_INIT_POINTER() are meaningless for this code. Signed-off-by: Sean Christopherson Reviewed-by: Kai Huang --- arch/x86/include/asm/reboot.h | 5 +++-- arch/x86/kernel/reboot.c | 30 ++++++++++++++++++++++++------ arch/x86/kvm/vmx/vmx.c | 6 ++---- 3 files changed, 29 insertions(+), 12 deletions(-) diff --git a/arch/x86/include/asm/reboot.h b/arch/x86/include/asm/reboot.h index 2551baec927d..d9a38d379d18 100644 --- a/arch/x86/include/asm/reboot.h +++ b/arch/x86/include/asm/reboot.h @@ -25,8 +25,9 @@ void __noreturn machine_real_restart(unsigned int type); #define MRR_BIOS 0 #define MRR_APM 1 =20 -typedef void crash_vmclear_fn(void); -extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss; +typedef void (cpu_emergency_virt_cb)(void); +void cpu_emergency_register_virt_callback(cpu_emergency_virt_cb *callback); +void cpu_emergency_unregister_virt_callback(cpu_emergency_virt_cb *callbac= k); void cpu_emergency_disable_virtualization(void); =20 typedef void (*nmi_shootdown_cb)(int, struct pt_regs*); diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c index 299b970e5f82..739e09527dbb 100644 --- a/arch/x86/kernel/reboot.c +++ b/arch/x86/kernel/reboot.c @@ -794,17 +794,35 @@ void machine_crash_shutdown(struct pt_regs *regs) * * protected by rcu. */ -crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss; -EXPORT_SYMBOL_GPL(crash_vmclear_loaded_vmcss); +static cpu_emergency_virt_cb __rcu *cpu_emergency_virt_callback; + +void cpu_emergency_register_virt_callback(cpu_emergency_virt_cb *callback) +{ + if (WARN_ON_ONCE(rcu_access_pointer(cpu_emergency_virt_callback))) + return; + + rcu_assign_pointer(cpu_emergency_virt_callback, callback); +} +EXPORT_SYMBOL_GPL(cpu_emergency_register_virt_callback); + +void cpu_emergency_unregister_virt_callback(cpu_emergency_virt_cb *callbac= k) +{ + if (WARN_ON_ONCE(rcu_access_pointer(cpu_emergency_virt_callback) !=3D cal= lback)) + return; + + rcu_assign_pointer(cpu_emergency_virt_callback, NULL); + synchronize_rcu(); +} +EXPORT_SYMBOL_GPL(cpu_emergency_unregister_virt_callback); =20 static inline void cpu_crash_vmclear_loaded_vmcss(void) { - crash_vmclear_fn *do_vmclear_operation =3D NULL; + cpu_emergency_virt_cb *callback; =20 rcu_read_lock(); - do_vmclear_operation =3D rcu_dereference(crash_vmclear_loaded_vmcss); - if (do_vmclear_operation) - do_vmclear_operation(); + callback =3D rcu_dereference(cpu_emergency_virt_callback); + if (callback) + callback(); rcu_read_unlock(); } =20 diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 317f72baf0c3..fc9cdb4114cc 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -8547,8 +8547,7 @@ static void __vmx_exit(void) { allow_smaller_maxphyaddr =3D false; =20 - RCU_INIT_POINTER(crash_vmclear_loaded_vmcss, NULL); - synchronize_rcu(); + cpu_emergency_unregister_virt_callback(crash_vmclear_local_loaded_vmcss); =20 vmx_cleanup_l1d_flush(); } @@ -8598,8 +8597,7 @@ static int __init vmx_init(void) pi_init_cpu(cpu); } =20 - rcu_assign_pointer(crash_vmclear_loaded_vmcss, - crash_vmclear_local_loaded_vmcss); + cpu_emergency_register_virt_callback(crash_vmclear_local_loaded_vmcss); =20 vmx_check_vmcs12_offsets(); =20 --=20 2.40.1.606.ga4b1b128d6-goog