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 X-Spam-Level: X-Spam-Status: No, score=-20.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B554DC64E6A for ; Mon, 19 Jul 2021 15:57:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9E16A61406 for ; Mon, 19 Jul 2021 15:57:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347405AbhGSPQK (ORCPT ); Mon, 19 Jul 2021 11:16:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:40456 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245177AbhGSOr1 (ORCPT ); Mon, 19 Jul 2021 10:47:27 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id B513E6136D; Mon, 19 Jul 2021 15:23:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626708227; bh=EVtl3DQpMr+8kzgOJSeZTYtS123L4SiJJlDRRAR5rQg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=h89eH3dK/OKcR+4lFSj5tw9fsCtoHxKEU2xrdRkM07CMErigqFYUml2NRytLqjVdp g9QQ4A2PAGIDYRuLO8v6YBYtxKXfgQeEzyPbompHLYH3xHPV3ZaYaTTm/Uuq9mk8AF khz16/OfWEbUgmvrmWRyAKEhy5w5o/D3YJfT9fD4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Lai Jiangshan , Paolo Bonzini Subject: [PATCH 4.14 231/315] KVM: X86: Disable hardware breakpoints unconditionally before kvm_x86->run() Date: Mon, 19 Jul 2021 16:52:00 +0200 Message-Id: <20210719144951.016562972@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210719144942.861561397@linuxfoundation.org> References: <20210719144942.861561397@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lai Jiangshan commit f85d40160691881a17a397c448d799dfc90987ba upstream. When the host is using debug registers but the guest is not using them nor is the guest in guest-debug state, the kvm code does not reset the host debug registers before kvm_x86->run(). Rather, it relies on the hardware vmentry instruction to automatically reset the dr7 registers which ensures that the host breakpoints do not affect the guest. This however violates the non-instrumentable nature around VM entry and exit; for example, when a host breakpoint is set on vcpu->arch.cr2, Another issue is consistency. When the guest debug registers are active, the host breakpoints are reset before kvm_x86->run(). But when the guest debug registers are inactive, the host breakpoints are delayed to be disabled. The host tracing tools may see different results depending on what the guest is doing. To fix the problems, we clear %db7 unconditionally before kvm_x86->run() if the host has set any breakpoints, no matter if the guest is using them or not. Signed-off-by: Lai Jiangshan Message-Id: <20210628172632.81029-1-jiangshanlai@gmail.com> Cc: stable@vger.kernel.org [Only clear %db7 instead of reloading all debug registers. - Paolo] Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 2 ++ 1 file changed, 2 insertions(+) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7237,6 +7237,8 @@ static int vcpu_enter_guest(struct kvm_v set_debugreg(vcpu->arch.eff_db[3], 3); set_debugreg(vcpu->arch.dr6, 6); vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_RELOAD; + } else if (unlikely(hw_breakpoint_active())) { + set_debugreg(0, 7); } kvm_x86_ops->run(vcpu);