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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C4D3FC433EF for ; Wed, 20 Jul 2022 03:15:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236159AbiGTDPs (ORCPT ); Tue, 19 Jul 2022 23:15:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48102 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242648AbiGTDPG (ORCPT ); Tue, 19 Jul 2022 23:15:06 -0400 Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ECBAB323; Tue, 19 Jul 2022 20:12:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1658286744; x=1689822744; h=message-id:subject:from:to:cc:date:in-reply-to: references:content-transfer-encoding:mime-version; bh=ySMjzh3NsTJKTRrIejBJDaESWOXt7P0Fuvi7p6w8yJ0=; b=fvqXHNxyKJBi4fyA1OQ2GWC6m4ZXZ4KeGJ+2j2Ad7GL3BGZYcbS8F+8s WO6ECzg4F6u9JuAg03VrxCGy5xURWH/WihjJaYKU/fOW9v9GWGJeqb6IH K5fVu3LwO8i7cwYKG+kL5//z1QidnrRsZc4rJw8xeG0vh9vEe1mFmwbpQ GGWoI07305MfRmR1e5vjE8jF1gI4I5DVxKcUoUko0dZAsxHy0p+sMX4+o zbiDYVUAWoMK8+Koz3w3rRU04BfK7dG6EMqwthyFPlJk+8msDNZbyDALp 01oaJZzrlgG0fRbCZi/S01MZrS0aXRUW6ruea8gV4hHWAucaStTP3QzNZ g==; X-IronPort-AV: E=McAfee;i="6400,9594,10413"; a="269693302" X-IronPort-AV: E=Sophos;i="5.92,285,1650956400"; d="scan'208";a="269693302" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Jul 2022 20:12:21 -0700 X-IronPort-AV: E=Sophos;i="5.92,285,1650956400"; d="scan'208";a="630603712" Received: from ecurtis-mobl.amr.corp.intel.com (HELO khuang2-desk.gar.corp.intel.com) ([10.213.162.137]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Jul 2022 20:12:18 -0700 Message-ID: Subject: Re: [PATCH v7 036/102] KVM: x86/mmu: Allow non-zero value for non-present SPTE From: Kai Huang To: Isaku Yamahata , isaku.yamahata@intel.com Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Paolo Bonzini , Sean Christopherson , Yuan Yao Date: Wed, 20 Jul 2022 15:12:16 +1200 In-Reply-To: <20220714184111.GT1379820@ls.amr.corp.intel.com> References: <20220714184111.GT1379820@ls.amr.corp.intel.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.44.3 (3.44.3-1.fc36) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org > --- a/arch/x86/kvm/mmu/spte.c > +++ b/arch/x86/kvm/mmu/spte.c > @@ -36,6 +36,9 @@ u64 __read_mostly shadow_present_mask; > u64 __read_mostly shadow_me_value; > u64 __read_mostly shadow_me_mask; > u64 __read_mostly shadow_acc_track_mask; > +#ifdef CONFIG_X86_64 > +u64 __read_mostly shadow_nonpresent_value; > +#endif Is this ever used? > =20 > u64 __read_mostly shadow_nonpresent_or_rsvd_mask; > u64 __read_mostly shadow_nonpresent_or_rsvd_lower_gfn_mask; > @@ -360,7 +363,7 @@ void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 m= mio_mask, u64 access_mask) > * not set any RWX bits. > */ > if (WARN_ON((mmio_value & mmio_mask) !=3D mmio_value) || > - WARN_ON(mmio_value && (REMOVED_SPTE & mmio_mask) =3D=3D mmio_value)= ) > + WARN_ON(mmio_value && (__REMOVED_SPTE & mmio_mask) =3D=3D mmio_valu= e)) > mmio_value =3D 0; This chunk doesn't look right, or necessary. We need mmio_mask/mmio_value = which causes EPT violation but with "suppress #VE" bit clear. =20 So, actually, we want to make sure SHADOW_NONPRESENT_VALUE is *NOT* in mmio= _mask and mmio_value. Using (REMOVED_SPTE & mmio_mask) =3D=3D mmio_value can act= ually ensure SHADOW_NONPRESENT_VALUE is never set in MMIO spte, correct? So I th= ink using REMOVED_SPTE is fine. Or maybe additionally adding a explicit check is even better: if (WARN_ON(mmio_mask & SHADOW_NONPRESENT_VALUE)) mmio_value =3D 0; But this change maybe should be in another patch which deals setting up per= -VM mmio_mask/mmio_value anyway. This patch, instead, focuses on allowing non-= zero value for non-present SPTE.