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=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 4919CC43381 for ; Fri, 22 Mar 2019 12:25:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1AA3B2054F for ; Fri, 22 Mar 2019 12:25:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553257542; bh=+1PYINcUFQ56bOHgp+tVwe2tJ9XzuE/XqUX17EGUyL4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=PMdjNP+2W1T7K7iXncMgxvb3M8a/f97Xyjx841C/LZaFmVS8PV/Jzf6sVmsfAZiG6 94G12op2xNrJe+XXRrTI67ipzWaxDMVP6v9Dtg2tT6vsf3KuVSLI47pDMiOfhRTsZZ qJCcEwrsGAqtdfCuI/a8ewVRIePR/xvUfYh2ouc0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391160AbfCVMXq (ORCPT ); Fri, 22 Mar 2019 08:23:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:35206 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390655AbfCVMXj (ORCPT ); Fri, 22 Mar 2019 08:23:39 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 95479218A1; Fri, 22 Mar 2019 12:23:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553257419; bh=+1PYINcUFQ56bOHgp+tVwe2tJ9XzuE/XqUX17EGUyL4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Tq5O+YLj3ro8258MaOwQIPEZqcg2wRR5LzTI0p1+FV/bxHUAKOjUadQNA8IHkLb8Z N59PDEyvv2+GogK3Zj90q5tPnphO1GlcuGKp2kc7YUbmFF6KSWCQsDoXEvnqM9KuWg ZxO11FKMCmu2Pu40P5bUIa4dnDqlG5a2qY4JkcBk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jim Mattson , Konrad Rzeszutek Wilk , Sean Christopherson , Paolo Bonzini Subject: [PATCH 5.0 225/238] KVM: VMX: Compare only a single byte for VMCS "launched" in vCPU-run Date: Fri, 22 Mar 2019 12:17:24 +0100 Message-Id: <20190322111311.621105920@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190322111258.383569278@linuxfoundation.org> References: <20190322111258.383569278@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 5.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sean Christopherson commit 61c08aa9606d4e48a8a50639c956448a720174c3 upstream. The vCPU-run asm blob does a manual comparison of a VMCS' launched status to execute the correct VM-Enter instruction, i.e. VMLAUNCH vs. VMRESUME. The launched flag is a bool, which is a typedef of _Bool. C99 does not define an exact size for _Bool, stating only that is must be large enough to hold '0' and '1'. Most, if not all, compilers use a single byte for _Bool, including gcc[1]. Originally, 'launched' was of type 'int' and so the asm blob used 'cmpl' to check the launch status. When 'launched' was moved to be stored on a per-VMCS basis, struct vcpu_vmx's "temporary" __launched flag was added in order to avoid having to pass the current VMCS into the asm blob. The new '__launched' was defined as a 'bool' and not an 'int', but the 'cmp' instruction was not updated. This has not caused any known problems, likely due to compilers aligning variables to 4-byte or 8-byte boundaries and KVM zeroing out struct vcpu_vmx during allocation. I.e. vCPU-run accesses "junk" data, it just happens to always be zero and so doesn't affect the result. [1] https://gcc.gnu.org/ml/gcc-patches/2000-10/msg01127.html Fixes: d462b8192368 ("KVM: VMX: Keep list of loaded VMCSs, instead of vcpus") Cc: Reviewed-by: Jim Mattson Reviewed-by: Konrad Rzeszutek Wilk Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/vmx/vmx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6399,7 +6399,7 @@ static void __vmx_vcpu_run(struct kvm_vc "mov %%" _ASM_AX", %%cr2 \n\t" "3: \n\t" /* Check if vmlaunch or vmresume is needed */ - "cmpl $0, %c[launched](%%" _ASM_CX ") \n\t" + "cmpb $0, %c[launched](%%" _ASM_CX ") \n\t" /* Load guest registers. Don't clobber flags. */ "mov %c[rax](%%" _ASM_CX "), %%" _ASM_AX " \n\t" "mov %c[rbx](%%" _ASM_CX "), %%" _ASM_BX " \n\t"