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[2620:137:e000::1:20]) by mx.google.com with ESMTP id v24-20020a63f218000000b005578994f212si3710467pgh.425.2023.07.21.14.33.18; Fri, 21 Jul 2023 14:33:32 -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=20221208 header.b=lupqznqf; 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 S230502AbjGUUVU (ORCPT + 99 others); Fri, 21 Jul 2023 16:21:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38862 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231311AbjGUUUy (ORCPT ); Fri, 21 Jul 2023 16:20:54 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F04883AA2 for ; Fri, 21 Jul 2023 13:20:02 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id 3f1490d57ef6-c8f360a07a2so2266429276.2 for ; Fri, 21 Jul 2023 13:20:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1689970783; x=1690575583; 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=f1LNi9Sq5NIBXtzGJVGKttDHRo4VG7MGlit5nvyUtF0=; b=lupqznqfPScgKgAlsl68k2HwQOWYVzqFz7+e39gz+UVj6wvvC+ma4BNLkDyLgMbDCr sXcaIXufKIRqTjEo6kaASseH4LuovJPFo1FpnMySbHlymLZC8toxxIjvN2Aiw4ju6EAG VaD/mWdhEO8ur/DDeO9tEnMiMm8VItIJH8OP+EP+LpWzQ/NrR5L8c8s2LMhTcLypPS2U oBg+8IvkdXfhKuyTvHG3Xef0QbwUQ6ZzSvJM7Mo/H4jFrr/vFd5FgUJyl+qeE3dTtsH5 MY6DHfpkgF/82Qh+aTdBRtINfnVpzFGxerBDIxZVXvcHDxqf5FZ0G6Srcd0y+VCH+a4h +9CA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689970783; x=1690575583; 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=f1LNi9Sq5NIBXtzGJVGKttDHRo4VG7MGlit5nvyUtF0=; b=UE9jJl4FmdRBt8lVAb8J0GqHbC9FtiPMgkofkW2dh9ugrklT4sy1td/iXtfna/RJT6 GjIIlvu9TU/QzVZjrCtQV0WWwWsJoW7OjVbg64Uo7lNcafxofTJSaV0iJOkiWCsKXyhA ADcT2SYT6+W5mMeExzrQaeFzsPU9aB5cBZNbUReCOuQy7hk78nQuLe5Bh1zm/R6nZse5 9uZKmtqkXjtDI4Su8ShA6TvfBm3cUjhllE5bFq4ksGoXWvC+/sucbPauPpYaO6erEq/s ladM1OwD4Q1SJck+Pc8pU8p6WCQPHvnF/rY4oqd15+oCeE/vtHSqruVikiHbLxfUzjLI BR2w== X-Gm-Message-State: ABy/qLYiejwXCdiKng84QDxgOLtaZUQFWEEVF3pGVngPUNnd8ijDShwK f4PlfqIVhNQARc8ZvT4EYh4LpbWwP4k= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a5b:bc2:0:b0:ce9:64b3:80dc with SMTP id c2-20020a5b0bc2000000b00ce964b380dcmr18891ybr.1.1689970783817; Fri, 21 Jul 2023 13:19:43 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 21 Jul 2023 13:18:59 -0700 In-Reply-To: <20230721201859.2307736-1-seanjc@google.com> Mime-Version: 1.0 References: <20230721201859.2307736-1-seanjc@google.com> X-Mailer: git-send-email 2.41.0.487.g6d72f3e995-goog Message-ID: <20230721201859.2307736-20-seanjc@google.com> Subject: [PATCH v4 19/19] KVM: VMX: Skip VMCLEAR logic during emergency reboots if CR4.VMXE=0 From: Sean Christopherson To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Sean Christopherson , Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Andrew Cooper , Kai Huang , Chao Gao 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_BLOCKED,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE, 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: INBOX X-GMAIL-THRID: 1772067448268133010 X-GMAIL-MSGID: 1772067448268133010 Bail from vmx_emergency_disable() without processing the list of loaded VMCSes if CR4.VMXE=0, i.e. if the CPU can't be post-VMXON. It should be impossible for the list to have entries if VMX is already disabled, and even if that invariant doesn't hold, VMCLEAR will #UD anyways, i.e. processing the list is pointless even if it somehow isn't empty. Assuming no existing KVM bugs, this should be a glorified nop. The primary motivation for the change is to avoid having code that looks like it does VMCLEAR, but then skips VMXON, which is nonsensical. Suggested-by: Kai Huang Signed-off-by: Sean Christopherson Reviewed-by: Kai Huang --- arch/x86/kvm/vmx/vmx.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 5d21931842a5..0ef5ede9cb7c 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -773,12 +773,20 @@ static void vmx_emergency_disable(void) kvm_rebooting = true; + /* + * Note, CR4.VMXE can be _cleared_ in NMI context, but it can only be + * set in task context. If this races with VMX is disabled by an NMI, + * VMCLEAR and VMXOFF may #UD, but KVM will eat those faults due to + * kvm_rebooting set. + */ + if (!(__read_cr4() & X86_CR4_VMXE)) + return; + list_for_each_entry(v, &per_cpu(loaded_vmcss_on_cpu, cpu), loaded_vmcss_on_cpu_link) vmcs_clear(v->vmcs); - if (__read_cr4() & X86_CR4_VMXE) - kvm_cpu_vmxoff(); + kvm_cpu_vmxoff(); } static void __loaded_vmcs_clear(void *arg)