From patchwork Mon Jul 12 06:02:35 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 474116 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=-19.4 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, 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 631CAC11F66 for ; Mon, 12 Jul 2021 06:57:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4CF2A61004 for ; Mon, 12 Jul 2021 06:57:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238721AbhGLHAe (ORCPT ); Mon, 12 Jul 2021 03:00:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:33184 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239913AbhGLG6c (ORCPT ); Mon, 12 Jul 2021 02:58:32 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 50DEC61156; Mon, 12 Jul 2021 06:55:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626072944; bh=ArcNppnFTpmo6YFXLOP+cvlzWMFdiDntTxV/feCOl3w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AV14hT7ZTOtxDGGK0M7/fTqDrwMcn+S2C83UhAcMyOATmvtYNNPgQkRbbJZzyuhFm FadTImylHE5McYCAOgqm7ZfLmBEknnMKref/ACkj28Nohgs8rdrG1T7rcWSmzo3hPf qM2Y+v2MXaRt4Qc7EyXojVsk922xXJ9YUBcLV+WQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sean Christopherson , Paolo Bonzini Subject: [PATCH 5.12 072/700] KVM: x86/mmu: Treat NX as used (not reserved) for all !TDP shadow MMUs Date: Mon, 12 Jul 2021 08:02:35 +0200 Message-Id: <20210712060934.879718606@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210712060924.797321836@linuxfoundation.org> References: <20210712060924.797321836@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Sean Christopherson commit 112022bdb5bc372e00e6e43cb88ee38ea67b97bd upstream. Mark NX as being used for all non-nested shadow MMUs, as KVM will set the NX bit for huge SPTEs if the iTLB mutli-hit mitigation is enabled. Checking the mitigation itself is not sufficient as it can be toggled on at any time and KVM doesn't reset MMU contexts when that happens. KVM could reset the contexts, but that would require purging all SPTEs in all MMUs, for no real benefit. And, KVM already forces EFER.NX=1 when TDP is disabled (for WP=0, SMEP=1, NX=0), so technically NX is never reserved for shadow MMUs. Fixes: b8e8c8303ff2 ("kvm: mmu: ITLB_MULTIHIT mitigation") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Message-Id: <20210622175739.3610207-3-seanjc@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/mmu/mmu.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4155,7 +4155,15 @@ static inline u64 reserved_hpa_bits(void void reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context) { - bool uses_nx = context->nx || + /* + * KVM uses NX when TDP is disabled to handle a variety of scenarios, + * notably for huge SPTEs if iTLB multi-hit mitigation is enabled and + * to generate correct permissions for CR0.WP=0/CR4.SMEP=1/EFER.NX=0. + * The iTLB multi-hit workaround can be toggled at any time, so assume + * NX can be used by any non-nested shadow MMU to avoid having to reset + * MMU contexts. Note, KVM forces EFER.NX=1 when TDP is disabled. + */ + bool uses_nx = context->nx || !tdp_enabled || context->mmu_role.base.smep_andnot_wp; struct rsvd_bits_validate *shadow_zero_check; int i;